Search Techniques for the Web of Things: A Taxonomy and Survey
Identifieur interne : 000014 ( Pmc/Checkpoint ); précédent : 000013; suivant : 000015Search Techniques for the Web of Things: A Taxonomy and Survey
Auteurs : Yuchao Zhou ; Suparna De ; Wei Wang ; Klaus MoessnerSource :
- Sensors (Basel, Switzerland) [ 1424-8220 ] ; 2016.
Abstract
The Web of Things aims to make physical world objects and their data accessible through standard Web technologies to enable intelligent applications and sophisticated data analytics. Due to the amount and heterogeneity of the data, it is challenging to perform data analysis directly; especially when the data is captured from a large number of distributed sources. However, the size and scope of the data can be reduced and narrowed down with search techniques, so that only the most relevant and useful data items are selected according to the application requirements. Search is fundamental to the Web of Things while challenging by nature in this context, e.g., mobility of the objects, opportunistic presence and sensing, continuous data streams with changing spatial and temporal properties, efficient indexing for historical and real time data. The research community has developed numerous techniques and methods to tackle these problems as reported by a large body of literature in the last few years. A comprehensive investigation of the current and past studies is necessary to gain a clear view of the research landscape and to identify promising future directions. This survey reviews the state-of-the-art search methods for the Web of Things, which are classified according to three different viewpoints: basic principles, data/knowledge representation, and contents being searched. Experiences and lessons learned from the existing work and some EU research projects related to Web of Things are discussed, and an outlook to the future research is presented.
Url:
DOI: 10.3390/s16050600
PubMed: 27128918
PubMed Central: 4883291
Affiliations:
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<record><TEI><teiHeader><fileDesc><titleStmt><title xml:lang="en">Search Techniques for the Web of Things: A Taxonomy and Survey</title><author><name sortKey="Zhou, Yuchao" sort="Zhou, Yuchao" uniqKey="Zhou Y" first="Yuchao" last="Zhou">Yuchao Zhou</name><affiliation><nlm:aff id="af1-sensors-16-00600">Institute for Communication Systems (ICS), University of Surrey, Guildford GU2 7XH, UK;<email>s.de@surrey.ac.uk</email> (S.D.);<email>k.moessner@surrey.ac.uk</email> (K.M.)</nlm:aff></affiliation></author><author><name sortKey="De, Suparna" sort="De, Suparna" uniqKey="De S" first="Suparna" last="De">Suparna De</name><affiliation><nlm:aff id="af1-sensors-16-00600">Institute for Communication Systems (ICS), University of Surrey, Guildford GU2 7XH, UK;<email>s.de@surrey.ac.uk</email> (S.D.);<email>k.moessner@surrey.ac.uk</email> (K.M.)</nlm:aff></affiliation></author><author><name sortKey="Wang, Wei" sort="Wang, Wei" uniqKey="Wang W" first="Wei" last="Wang">Wei Wang</name><affiliation><nlm:aff id="af2-sensors-16-00600">Department of Computer Science and Software Engineering, Xi’an Jiaotong-Liverpool University, Ren’ai Road Dushu Lake Higher Education Town SIP, Suzhou 215123, China;<email>Wei.Wang03@xjtlu.edu.cn</email></nlm:aff></affiliation></author><author><name sortKey="Moessner, Klaus" sort="Moessner, Klaus" uniqKey="Moessner K" first="Klaus" last="Moessner">Klaus Moessner</name><affiliation><nlm:aff id="af1-sensors-16-00600">Institute for Communication Systems (ICS), University of Surrey, Guildford GU2 7XH, UK;<email>s.de@surrey.ac.uk</email> (S.D.);<email>k.moessner@surrey.ac.uk</email> (K.M.)</nlm:aff></affiliation></author></titleStmt><publicationStmt><idno type="wicri:source">PMC</idno><idno type="pmid">27128918</idno><idno type="pmc">4883291</idno><idno type="url">http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4883291</idno><idno type="RBID">PMC:4883291</idno><idno type="doi">10.3390/s16050600</idno><date when="2016">2016</date><idno type="wicri:Area/Pmc/Corpus">000131</idno><idno type="wicri:Area/Pmc/Curation">000131</idno><idno type="wicri:Area/Pmc/Checkpoint">000014</idno></publicationStmt><sourceDesc><biblStruct><analytic><title xml:lang="en" level="a" type="main">Search Techniques for the Web of Things: A Taxonomy and Survey</title><author><name sortKey="Zhou, Yuchao" sort="Zhou, Yuchao" uniqKey="Zhou Y" first="Yuchao" last="Zhou">Yuchao Zhou</name><affiliation><nlm:aff id="af1-sensors-16-00600">Institute for Communication Systems (ICS), University of Surrey, Guildford GU2 7XH, UK;<email>s.de@surrey.ac.uk</email> (S.D.);<email>k.moessner@surrey.ac.uk</email> (K.M.)</nlm:aff></affiliation></author><author><name sortKey="De, Suparna" sort="De, Suparna" uniqKey="De S" first="Suparna" last="De">Suparna De</name><affiliation><nlm:aff id="af1-sensors-16-00600">Institute for Communication Systems (ICS), University of Surrey, Guildford GU2 7XH, UK;<email>s.de@surrey.ac.uk</email> (S.D.);<email>k.moessner@surrey.ac.uk</email> (K.M.)</nlm:aff></affiliation></author><author><name sortKey="Wang, Wei" sort="Wang, Wei" uniqKey="Wang W" first="Wei" last="Wang">Wei Wang</name><affiliation><nlm:aff id="af2-sensors-16-00600">Department of Computer Science and Software Engineering, Xi’an Jiaotong-Liverpool University, Ren’ai Road Dushu Lake Higher Education Town SIP, Suzhou 215123, China;<email>Wei.Wang03@xjtlu.edu.cn</email></nlm:aff></affiliation></author><author><name sortKey="Moessner, Klaus" sort="Moessner, Klaus" uniqKey="Moessner K" first="Klaus" last="Moessner">Klaus Moessner</name><affiliation><nlm:aff id="af1-sensors-16-00600">Institute for Communication Systems (ICS), University of Surrey, Guildford GU2 7XH, UK;<email>s.de@surrey.ac.uk</email> (S.D.);<email>k.moessner@surrey.ac.uk</email> (K.M.)</nlm:aff></affiliation></author></analytic><series><title level="j">Sensors (Basel, Switzerland)</title><idno type="eISSN">1424-8220</idno><imprint><date when="2016">2016</date></imprint></series></biblStruct></sourceDesc></fileDesc><profileDesc><textClass></textClass></profileDesc></teiHeader><front><div type="abstract" xml:lang="en"><p>The Web of Things aims to make physical world objects and their data accessible through standard Web technologies to enable intelligent applications and sophisticated data analytics. Due to the amount and heterogeneity of the data, it is challenging to perform data analysis directly; especially when the data is captured from a large number of distributed sources. However, the size and scope of the data can be reduced and narrowed down with search techniques, so that only the most relevant and useful data items are selected according to the application requirements. Search is fundamental to the Web of Things while challenging by nature in this context, e.g., mobility of the objects, opportunistic presence and sensing, continuous data streams with changing spatial and temporal properties, efficient indexing for historical and real time data. The research community has developed numerous techniques and methods to tackle these problems as reported by a large body of literature in the last few years. A comprehensive investigation of the current and past studies is necessary to gain a clear view of the research landscape and to identify promising future directions. This survey reviews the state-of-the-art search methods for the Web of Things, which are classified according to three different viewpoints: basic principles, data/knowledge representation, and contents being searched. Experiences and lessons learned from the existing work and some EU research projects related to Web of Things are discussed, and an outlook to the future research is presented.</p></div></front><back><div1 type="bibliography"><listBibl><biblStruct><analytic><author><name sortKey="Guinard, D" uniqKey="Guinard D">D. Guinard</name></author><author><name sortKey="Trifa, V" uniqKey="Trifa V">V. Trifa</name></author></analytic></biblStruct><biblStruct><analytic><author><name sortKey="Zeng, D" uniqKey="Zeng D">D. Zeng</name></author><author><name sortKey="Guo, S" uniqKey="Guo S">S. Guo</name></author><author><name sortKey="Cheng, Z" uniqKey="Cheng Z">Z. Cheng</name></author></analytic></biblStruct><biblStruct><analytic><author><name sortKey="Evans, D" uniqKey="Evans D">D. 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<front><journal-meta><journal-id journal-id-type="nlm-ta">Sensors (Basel)</journal-id><journal-id journal-id-type="iso-abbrev">Sensors (Basel)</journal-id><journal-id journal-id-type="publisher-id">sensors</journal-id><journal-title-group><journal-title>Sensors (Basel, Switzerland)</journal-title></journal-title-group><issn pub-type="epub">1424-8220</issn><publisher><publisher-name>MDPI</publisher-name></publisher></journal-meta><article-meta><article-id pub-id-type="pmid">27128918</article-id><article-id pub-id-type="pmc">4883291</article-id><article-id pub-id-type="doi">10.3390/s16050600</article-id><article-id pub-id-type="publisher-id">sensors-16-00600</article-id><article-categories><subj-group subj-group-type="heading"><subject>Review</subject></subj-group></article-categories><title-group><article-title>Search Techniques for the Web of Things: A Taxonomy and Survey</article-title></title-group><contrib-group><contrib contrib-type="author"><name><surname>Zhou</surname><given-names>Yuchao</given-names></name><xref ref-type="aff" rid="af1-sensors-16-00600">1</xref><xref rid="c1-sensors-16-00600" ref-type="corresp">*</xref></contrib><contrib contrib-type="author"><name><surname>De</surname><given-names>Suparna</given-names></name><xref ref-type="aff" rid="af1-sensors-16-00600">1</xref></contrib><contrib contrib-type="author"><name><surname>Wang</surname><given-names>Wei</given-names></name><xref ref-type="aff" rid="af2-sensors-16-00600">2</xref></contrib><contrib contrib-type="author"><name><surname>Moessner</surname><given-names>Klaus</given-names></name><xref ref-type="aff" rid="af1-sensors-16-00600">1</xref></contrib></contrib-group><contrib-group><contrib contrib-type="editor"><name><surname>Sun</surname><given-names>Yunchuan</given-names></name><role>Academic Editor</role></contrib><contrib contrib-type="editor"><name><surname>Jara</surname><given-names>Antonio</given-names></name><role>Academic Editor</role></contrib><contrib contrib-type="editor"><name><surname>Wang</surname><given-names>Shengling</given-names></name><role>Academic Editor</role></contrib></contrib-group><aff id="af1-sensors-16-00600"><label>1</label>Institute for Communication Systems (ICS), University of Surrey, Guildford GU2 7XH, UK;<email>s.de@surrey.ac.uk</email> (S.D.);<email>k.moessner@surrey.ac.uk</email> (K.M.)</aff><aff id="af2-sensors-16-00600"><label>2</label>Department of Computer Science and Software Engineering, Xi’an Jiaotong-Liverpool University, Ren’ai Road Dushu Lake Higher Education Town SIP, Suzhou 215123, China;<email>Wei.Wang03@xjtlu.edu.cn</email></aff><author-notes><corresp id="c1-sensors-16-00600"><label>*</label>Correspondence: <email>yuchao.zhou@surrey.ac.uk</email>; Tel.: +44-750-088-9377</corresp></author-notes><pub-date pub-type="epub"><day>27</day><month>4</month><year>2016</year></pub-date><pub-date pub-type="collection"><month>5</month><year>2016</year></pub-date><volume>16</volume><issue>5</issue><elocation-id>600</elocation-id><history><date date-type="received"><day>18</day><month>1</month><year>2016</year></date><date date-type="accepted"><day>21</day><month>4</month><year>2016</year></date></history><permissions><copyright-statement>© 2016 by the authors; licensee MDPI, Basel, Switzerland.</copyright-statement><copyright-year>2016</copyright-year><license><license-p><pmc-comment>CREATIVE COMMONS</pmc-comment>This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC-BY) license (<ext-link ext-link-type="uri" xlink:href="http://creativecommons.org/licenses/by/4.0/">http://creativecommons.org/licenses/by/4.0/</ext-link>).</license-p></license></permissions><abstract><p>The Web of Things aims to make physical world objects and their data accessible through standard Web technologies to enable intelligent applications and sophisticated data analytics. Due to the amount and heterogeneity of the data, it is challenging to perform data analysis directly; especially when the data is captured from a large number of distributed sources. However, the size and scope of the data can be reduced and narrowed down with search techniques, so that only the most relevant and useful data items are selected according to the application requirements. Search is fundamental to the Web of Things while challenging by nature in this context, e.g., mobility of the objects, opportunistic presence and sensing, continuous data streams with changing spatial and temporal properties, efficient indexing for historical and real time data. The research community has developed numerous techniques and methods to tackle these problems as reported by a large body of literature in the last few years. A comprehensive investigation of the current and past studies is necessary to gain a clear view of the research landscape and to identify promising future directions. This survey reviews the state-of-the-art search methods for the Web of Things, which are classified according to three different viewpoints: basic principles, data/knowledge representation, and contents being searched. Experiences and lessons learned from the existing work and some EU research projects related to Web of Things are discussed, and an outlook to the future research is presented.</p></abstract><kwd-group><kwd>search</kwd><kwd>Web of Things</kwd><kwd>Internet of Things</kwd><kwd>linked data</kwd><kwd>streaming data</kwd><kwd>observation and measurement data</kwd><kwd>sensors</kwd><kwd>entities</kwd></kwd-group></article-meta></front><floats-group><fig id="sensors-16-00600-f001" position="float"><label>Figure 1</label><caption><p>Classifications of the Search Techniques in WoT.</p></caption><graphic xlink:href="sensors-16-00600-g001"></graphic></fig><fig id="sensors-16-00600-f002" position="float"><label>Figure 2</label><caption><p>WoT System Model.</p></caption><graphic xlink:href="sensors-16-00600-g002"></graphic></fig><table-wrap id="sensors-16-00600-t001" position="float"><object-id pub-id-type="pii">sensors-16-00600-t001_Table 1</object-id><label>Table 1</label><caption><p>WoT Applications and Enabling Search Techniques.</p></caption><table frame="hsides" rules="groups"><thead><tr><th align="center" valign="middle" style="border-top:solid thin;border-bottom:solid thin" rowspan="1" colspan="1">Domain</th><th align="center" valign="middle" style="border-top:solid thin;border-bottom:solid thin" rowspan="1" colspan="1">Applications</th><th align="center" valign="middle" style="border-top:solid thin;border-bottom:solid thin" rowspan="1" colspan="1">Search Requirements</th><th align="center" valign="middle" style="border-top:solid thin;border-bottom:solid thin" rowspan="1" colspan="1">Search Techniques</th></tr></thead><tbody><tr><td align="left" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Smart Cities</td><td align="left" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Community-based Flood Monitoring; <break></break>Mobile Applications; <break></break>ollution Monitoring; <break></break>Public Rental Bicycle System; <break></break>Soil Monitoring; <break></break>Water Level Monitoring; <break></break>Weather Monitoring</td><td align="left" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Require search with multiple functionalities (e.g., search by descriptions, by locations, or others); <break></break>Require managing fast changing and updating of sensing data; <break></break>May require both real-time and historical data access; <break></break>Require data analysis/prediction; <break></break>Require handling of mobile objects and their states</td><td align="left" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Real-time Data Retrieval; <break></break>Entity Search; <break></break>Location-based Search; <break></break>Context-based Sensor Search</td></tr><tr><td align="left" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Home Automation</td><td align="left" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Adaptive Building Smart Control of Washing Machine</td><td align="left" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Dynamical selection of the surrounding/affecting resources Discovery of devices</td><td align="left" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Entity Search Sensor Search</td></tr><tr><td align="left" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Manufacturing</td><td align="left" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Lifecycle Management for Industrial Automation Systems</td><td align="left" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">The discovery needs to be enabled in a dynamic environment where physical resources appear and disappear during lifecycle phases.</td><td align="left" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Context-based Search</td></tr><tr><td align="left" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Smart Grids</td><td align="left" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Virtual Power Plants</td><td align="left" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Require dynamically finding operateable distributed energy resources</td><td align="left" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Entity Search</td></tr><tr><td align="left" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Network Management</td><td align="left" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Device, Network, and Application Management</td><td align="left" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Require finding all devices that have a certain set of properties.</td><td align="left" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Context-based Search</td></tr></tbody></table></table-wrap><table-wrap id="sensors-16-00600-t002" position="float"><object-id pub-id-type="pii">sensors-16-00600-t002_Table 2</object-id><label>Table 2</label><caption><p>Comparison of Search Techniques According to Basic Principles Classification (Abbreviations are listed in the footer).</p></caption><table frame="hsides" rules="groups"><thead><tr><th align="center" valign="middle" style="border-top:solid thin;border-bottom:solid thin" rowspan="1" colspan="1">Classification</th><th align="center" valign="middle" style="border-top:solid thin;border-bottom:solid thin" rowspan="1" colspan="1">Search Technique</th><th align="center" valign="middle" style="border-top:solid thin;border-bottom:solid thin" rowspan="1" colspan="1">Data Format</th><th align="center" valign="middle" style="border-top:solid thin;border-bottom:solid thin" rowspan="1" colspan="1">Access Approach</th><th align="center" valign="middle" style="border-top:solid thin;border-bottom:solid thin" rowspan="1" colspan="1">Search Type</th><th align="center" valign="middle" style="border-top:solid thin;border-bottom:solid thin" rowspan="1" colspan="1">Scale of Experiments</th><th align="center" valign="middle" style="border-top:solid thin;border-bottom:solid thin" rowspan="1" colspan="1">D<sup>1</sup></th><th align="center" valign="middle" style="border-top:solid thin;border-bottom:solid thin" rowspan="1" colspan="1">Ar<sup>2</sup></th><th align="center" valign="middle" style="border-top:solid thin;border-bottom:solid thin" rowspan="1" colspan="1">Implementation</th><th align="center" valign="middle" style="border-top:solid thin;border-bottom:solid thin" rowspan="1" colspan="1">Remarks</th></tr></thead><tbody><tr><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Text Indexing</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">GSN [<xref rid="B25-sensors-16-00600" ref-type="bibr">25</xref>]</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Virtual sensors in XML</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">HTTP REST</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Keyword-based search, SQL query with time window</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">-</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Yes</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Cen</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Java/MySQL</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Extended as XGSN [<xref rid="B26-sensors-16-00600" ref-type="bibr">26</xref>] for distributed data acquisition and semantic annotation. <break></break>Integrated with Link Sensor Middleware (LSM) [<xref rid="B27-sensors-16-00600" ref-type="bibr">27</xref>] in OpenIoT [<xref rid="B28-sensors-16-00600" ref-type="bibr">28</xref>] project</td></tr><tr><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Text Indexing</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">SenseWeb [<xref rid="B29-sensors-16-00600" ref-type="bibr">29</xref>]</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Sensor ontology (an extension of the namespace defined by OGC SWE)</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Map display with text description </td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Keyword/spatial search</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">-</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Yes</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Cen</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">-</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Many applications described but none accessible</td></tr><tr><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Text Indexing</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Dyser [<xref rid="B30-sensors-16-00600" ref-type="bibr">30</xref>]</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Virtual sensors (microformat)</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">URL/HTTP/HTML</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Keyword-based/value-based</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">385 sensors over 5 months</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Yes</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Cen</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Java/PHP</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Query of state of real world objects; <break></break>Computation required for state awareness, the scale is limited to a small number of sensors</td></tr><tr><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Text Indexing</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Microsearch [<xref rid="B31-sensors-16-00600" ref-type="bibr">31</xref>] <break></break>Snoogle [<xref rid="B32-sensors-16-00600" ref-type="bibr">32</xref>]</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Direct communication with sensor motes with built-in metadata </td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Virtual sensors in built-in format</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Keyword-based top-k search</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">-</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Yes</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Dis</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">TelosB motes</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Early search implementations with limited functionalities and limited scalability</td></tr><tr><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Text Indexing</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">LiveWeb [<xref rid="B33-sensors-16-00600" ref-type="bibr">33</xref>]</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Sensor data in XML</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">HTML/AJAX</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Real-time content search based on keywords, category, and value range </td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">-</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Yes</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Cen</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">PHP/Java/Apache/MySQL</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Practical implementation without evaluation Should fit in global scale</td></tr><tr><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Text Indexing</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">lmDNS-SD [<xref rid="B34-sensors-16-00600" ref-type="bibr">34</xref>]</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Extended DNS record for sensors and objects</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">List of sensors</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Resource directory based on DNS-SD</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">-</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Yes</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">P2P</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">-</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Existing Internet standards utilised, thus fit in Web scale</td></tr><tr><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Text Indexing</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">DNS Search [<xref rid="B35-sensors-16-00600" ref-type="bibr">35</xref>]</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Extended DNS record for sensors</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">HTTP REST/WADL</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">URL and DNS-based (type/location)</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">250,000 zones</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Yes</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Dis</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">BIND/MySQL</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Utilise DNS structure; fit in Global scale</td></tr><tr><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Text Indexing <break></break>Spatial Indexing</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Mobile Digcovery [<xref rid="B36-sensors-16-00600" ref-type="bibr">36</xref>]</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Integration of Multi-types</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">JSON-based response</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Multi-functional JSON-based query</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">-</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Yes</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Dis</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">ElasticSearch</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Combination of search engine and Web Infrastructure</td></tr><tr><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Text Indexing <break></break>Spatial Indexing</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">IoT-SVKSearch [<xref rid="B37-sensors-16-00600" ref-type="bibr">37</xref>]</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Sampling values with metadata in Raw Data Store</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Data in built-in format</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Keyword-based (B<sup>+</sup>-tree), spatial-temporal (R-tree), value-based (B<sup>+</sup>-tree) search</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">140,800~352,000 sensors</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Yes</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Dec</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">PostgreSQL/file system</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Multiple search functionalities supported</td></tr><tr><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Text Indexing <break></break>Spatial Indexing</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">OSIRIS [<xref rid="B38-sensors-16-00600" ref-type="bibr">38</xref>]</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">OGC SWE Sensor model and data model</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">SWE services</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Spatial, temporal and keyword-based search</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">-</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Yes</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Cen</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">JSI/Apache Lucene</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Applications in Smart City domain <break></break>Website of the project no longer accessible</td></tr><tr><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Spatial Indexing</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">SensorMap [<xref rid="B39-sensors-16-00600" ref-type="bibr">39</xref>]</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Direct communication with web accessible sensors</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Web services APIs</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Spatial search (based on COLR-tree/crawling)</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">-</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">-</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Cen</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">MSRSense toolkit</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">SenseWeb-based application, not accessible currently</td></tr><tr><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Spatial Indexing</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">GeoCENS [<xref rid="B40-sensors-16-00600" ref-type="bibr">40</xref>]</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">OGC SOS, SensorML, OGC O&M</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">SWE services</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Spatial search (Peano space filling curves)</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">~40,000 sensors/procedures</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Yes</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">P2P</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">-</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Designed for sensor data from smaller organizations or individuals</td></tr><tr><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Spatial Indexing</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Geographic Service Discovery [<xref rid="B41-sensors-16-00600" ref-type="bibr">41</xref>]</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Services with geo-information</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">HTTP REST</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Spatial search (R-tree index/category server)</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">3200 services</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Yes</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Dis</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Java</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">R-tree is combined with distributed architecture</td></tr><tr><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Spatial Indexing</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">FUTS Data Query [<xref rid="B42-sensors-16-00600" ref-type="bibr">42</xref>]</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Virtual Object ontology in OWL-DL</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">SenML/JSON</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Spatial search with time window/sensor type</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">20,000 sensors</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Yes</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Cen</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Java</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Cloud database for huge data storage</td></tr><tr><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Spatial Indexing</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Geospatial Indexing [<xref rid="B23-sensors-16-00600" ref-type="bibr">23</xref>]</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">OWL-S</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">SPARQL endpoint</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Semantic query (R-tree index)</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">10,000 services</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Yes</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Dis</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Java</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">R-tree and Semantic query combined</td></tr><tr><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Location-based Clustering</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">IoT Platform [<xref rid="B43-sensors-16-00600" ref-type="bibr">43</xref>]</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">SSN ontology/OWL-DL</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">SPARQL endpoint</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">SPARQL query</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">-</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Yes</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Cen</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Java/Apache Tomcat</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Demo in smart building, could be applied to a larger scale as well</td></tr><tr><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Location-based Clustering</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Linked Sensor Streams [<xref rid="B44-sensors-16-00600" ref-type="bibr">44</xref>]</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">RDF stream data</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">SPARQL query response</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Type/location based query (based on clustering)</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">20,000 stream data</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Yes</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Dis</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Java</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Evaluation provided for clustering, not for search</td></tr><tr><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Location-based Clustering</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">IoT Service Search [<xref rid="B45-sensors-16-00600" ref-type="bibr">45</xref>]</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">OWL-S</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Service access standard</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Semantic-based query (based on clustering)</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">7500 services</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">No</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Dis</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Java Web Application/ Apache Tomcat</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Mobile services may crash this architecture</td></tr><tr><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Location-based Clustering</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Web-based Infrastructure [<xref rid="B46-sensors-16-00600" ref-type="bibr">46</xref>]</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Microdata <break></break>Microformats</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">HTTP REST</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Keyword matching with scope</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">600 simulated sensors <break></break>100,000 resources</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">No</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Dis</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">ApacheBench</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Demo in smart building, mobile services may crash this architecture</td></tr><tr><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Location-based Clustering</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Geocasting [<xref rid="B47-sensors-16-00600" ref-type="bibr">47</xref>,<xref rid="B48-sensors-16-00600" ref-type="bibr">48</xref>,<xref rid="B49-sensors-16-00600" ref-type="bibr">49</xref>]</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">-</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">-</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Geolocation-based query</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">-</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Yes</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">P2P</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">-</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Flexible approach, no reliance on any model or architecture</td></tr><tr><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Non-location-based Clustering</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">WoT Search [<xref rid="B50-sensors-16-00600" ref-type="bibr">50</xref>]</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Virtual Object ontology in OWL-DL</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">-</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Search with user preference and geo-location (search by application or human)</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">-</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">-</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">-</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">-</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Technique not implemented</td></tr><tr><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Non-location-based Clustering</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">IoT Serv<break></break>ices Indexing [<xref rid="B51-sensors-16-00600" ref-type="bibr">51</xref>]</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Web services (DPWS)</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">REST/SOAP</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Functionality clusters, spatial query (SWC-tree), temporal query</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">1600 IoT-WS <break></break>50 clusters</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Yes</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Cen</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">C#/Matlab</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Clustering process does not scale when IoT-WSs increase</td></tr><tr><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Non-location-based Clustering</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">AntClust [<xref rid="B52-sensors-16-00600" ref-type="bibr">52</xref>]</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">SSN Ontology</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">SPARQL query response</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Ant clustering based on context</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">100,000 sensors</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Yes</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Cen</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">-</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Good performance on query time but may need a lot of time to deal with incoming data, thus may not be suitable for real-time search</td></tr></tbody></table><table-wrap-foot><fn><p><sup>1</sup> D is short for Dynamicity. <sup>2</sup> Ar is short for Architecture. Other abbreviations include AJAX: Asynchronous JavaScript and XML, Cen: Centralised, Dec: Decentralised, Dis: Distributed, DNS-SD: DNS Service Directory, DPWS: Devices Profile for Web Services, FUTS: Frequently Updated Timestamped and Structured, HTML: HyperText Markup Language, JSI: Java Spatial Index, JSON: JavaScript Object Notation, O&M-S: Semantically annotated O&M, OGC: Open Geospatial Consortium, OWL: Web Ontology Language, OWL-DL: OWL- Description Logics, OWL-S: Semantic Markup for Web Services, RDB: Relational Database, RDFS: RDF Schema, SenML: Sensor Markup Language, SML-S: Semantically annotated SensorML, SOAP: Simple Object Access Protocol, SOS: Sensor Observation Service, SWE: Sensor Web Enablement, WADL: Web Application Description Language, XML: eXtensible Markup Language.</p></fn></table-wrap-foot></table-wrap><table-wrap id="sensors-16-00600-t003" position="float"><object-id pub-id-type="pii">sensors-16-00600-t003_Table 3</object-id><label>Table 3</label><caption><p>Comparison of Search Techniques According to Data/Knowledge Representation (Abbreviations are listed in the footer of <xref ref-type="table" rid="sensors-16-00600-t002">Table 2</xref>).</p></caption><table frame="hsides" rules="groups"><thead><tr><th align="center" valign="middle" style="border-top:solid thin;border-bottom:solid thin" rowspan="1" colspan="1">Classification</th><th align="center" valign="middle" style="border-top:solid thin;border-bottom:solid thin" rowspan="1" colspan="1">Search Technique</th><th align="center" valign="middle" style="border-top:solid thin;border-bottom:solid thin" rowspan="1" colspan="1">Data Format</th><th align="center" valign="middle" style="border-top:solid thin;border-bottom:solid thin" rowspan="1" colspan="1">Access Approach</th><th align="center" valign="middle" style="border-top:solid thin;border-bottom:solid thin" rowspan="1" colspan="1">Search Type</th><th align="center" valign="middle" style="border-top:solid thin;border-bottom:solid thin" rowspan="1" colspan="1">Scale of Experiments</th><th align="center" valign="middle" style="border-top:solid thin;border-bottom:solid thin" rowspan="1" colspan="1">D<sup>1</sup></th><th align="center" valign="middle" style="border-top:solid thin;border-bottom:solid thin" rowspan="1" colspan="1">Ar<sup>2</sup></th><th align="center" valign="middle" style="border-top:solid thin;border-bottom:solid thin" rowspan="1" colspan="1">Implementation</th><th align="center" valign="middle" style="border-top:solid thin;border-bottom:solid thin" rowspan="1" colspan="1">Remarks</th></tr></thead><tbody><tr><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Centralised</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Linked Sensor Data [<xref rid="B53-sensors-16-00600" ref-type="bibr">53</xref>]</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">RDF</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">HTML/XML</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">SPARQL query</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">20,000 weather stations</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Yes</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Cen</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Virtuoso RDF</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Combination of Linked Data, sensors and sensor data</td></tr><tr><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Centralised</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">IoT-DS [<xref rid="B54-sensors-16-00600" ref-type="bibr">54</xref>]</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">RDF</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">SPARQL query response</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">SPARQL query</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">100,000 instances</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Yes</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Cen</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">-</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Proposed IoT directory is similar to IoT Gateway</td></tr><tr><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Centralised</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">SemSOS [<xref rid="B55-sensors-16-00600" ref-type="bibr">55</xref>]</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">RDF</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">SML-S/O&M-S</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">SOS query mapping to SPARQL query</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">20,000 sensors</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">No</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Cen</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Apache Jena </td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Mobile sensors are ignored</td></tr><tr><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Centralised</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">SemSOS [<xref rid="B56-sensors-16-00600" ref-type="bibr">56</xref>]</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">SWE based model in Linked Data</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">OGC SWE SOS</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Named location based query</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">20,000 weather stations </td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">No</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Cen</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">RDF2Go/Sesame</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Different implementation of SemSOS</td></tr><tr><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Centralised</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">LinkedGeoData [<xref rid="B57-sensors-16-00600" ref-type="bibr">57</xref>]</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">RDF</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">SPARQL endpoint <break></break>HTTP REST</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">SPARQL-like query</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">-</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Yes</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Cen</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Java</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Enables geolocation query as part of a SPARQL query <break></break>Online version available at [<xref rid="B58-sensors-16-00600" ref-type="bibr">58</xref>] </td></tr><tr><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Centralised</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">OWLIM-SE [<xref rid="B59-sensors-16-00600" ref-type="bibr">59</xref>]</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">RDF/RDFS/OWL</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">SPARQL endpoint</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">SPARQL-like query</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">-</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Yes</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Cen</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Java</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Enable geolocation query as part of a SPARQL query</td></tr><tr><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Centralised</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">GeoSPARQL [<xref rid="B60-sensors-16-00600" ref-type="bibr">60</xref>]</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">RDF</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">SPARQL endpoint</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">SPARQL-like query</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">-</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Yes</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Cen</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Apache Jena</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Enable geolocation query as part of a SPARQL query</td></tr><tr><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Federated</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">DARQ [<xref rid="B61-sensors-16-00600" ref-type="bibr">61</xref>]</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">RDF datasets</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">SPARQL query response</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">SPARQL query</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">-</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">No</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Dec</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Java</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Requires service descriptions of datasets <break></break>Supports limited queries</td></tr><tr><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Federated</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">ANAPSID [<xref rid="B62-sensors-16-00600" ref-type="bibr">62</xref>]</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">RDF datasets</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">SPARQL query response</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">SPARQL query</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">-</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">No</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Dec</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Python</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Requires predicates of datasets</td></tr><tr><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Federated</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">SPLENDID [<xref rid="B63-sensors-16-00600" ref-type="bibr">63</xref>]</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">RDF datasets</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">SPARQL query response</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">SPARQL query</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">-</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">No</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Dec</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Java</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Requires VoID of datasets</td></tr><tr><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Federated</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">FedX [<xref rid="B64-sensors-16-00600" ref-type="bibr">64</xref>]</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">RDF datasets</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">SPARQL query response</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">SPARQL query</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">-</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Yes</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Dec</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Java</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Easy to be extended as only the endpoint is required</td></tr><tr><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Federated</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Federated Query Implementation [<xref rid="B65-sensors-16-00600" ref-type="bibr">65</xref>]</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">RDF datasets</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">SPARQL query response</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">SPARQL query</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">-</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Yes</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Dec</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Java</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Easy to be extended as only the endpoint is required</td></tr><tr><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Federated</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">SPARQL 1.1 Federated Query [<xref rid="B66-sensors-16-00600" ref-type="bibr">66</xref>,<xref rid="B67-sensors-16-00600" ref-type="bibr">67</xref>]</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">RDF datasets</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">SPARQL query response</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">SPARQL query</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">-</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Yes</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Dis</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">-</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">W3C Recommendation for Federated Query</td></tr><tr><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">RDB Mapping</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">GSN [<xref rid="B25-sensors-16-00600" ref-type="bibr">25</xref>]</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Virtual sensors in XML</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">HTTP REST</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Keyword-based search, <break></break>SQL query with time window</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">-</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Yes</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Cen</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Java/MySQL</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Extended as XGSN [<xref rid="B26-sensors-16-00600" ref-type="bibr">26</xref>] for distributed data acquisition and semantic annotation. Integrated with Link Sensor Middleware (LSM) [<xref rid="B27-sensors-16-00600" ref-type="bibr">27</xref>] in OpenIoT [<xref rid="B28-sensors-16-00600" ref-type="bibr">28</xref>] project</td></tr><tr><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">RDB Mapping</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">SenseWeb [<xref rid="B29-sensors-16-00600" ref-type="bibr">29</xref>]</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Sensor ontology (an extension of the namespace defined by OGC SWE)</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Map display with text description </td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Keyword/spatial search</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">-</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Yes</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Cen</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">-</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Many applications described but none is accessible</td></tr><tr><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">RDB Mapping <break></break>Semantic Modelling</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">SPARQLstream [<xref rid="B68-sensors-16-00600" ref-type="bibr">68</xref>]</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">SSN ontology</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">SPARQL query response</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Continuous SPARQL query with time window</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">8000 data values/second</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Yes</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Cen</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">-</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Data mapped to DSMS</td></tr><tr><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Semantic Modelling</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">C-SPARQL [<xref rid="B69-sensors-16-00600" ref-type="bibr">69</xref>]</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">RDF streams</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">SPARQL query response</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Continuous SPARQL query (time window/ periodical execution)</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">-</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Yes</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Cen</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">-</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Data mapped to DSMS <break></break>No evaluation provided</td></tr><tr><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Semantic Modelling</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">EP-SPARQL [<xref rid="B70-sensors-16-00600" ref-type="bibr">70</xref>]</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">RDF and RDF event streams</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">SPARQL query response</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Continuous SPARQL query </td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">20,000 triples/20 locations</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Yes</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Cen</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Prolog language</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Designed for Event Processing</td></tr><tr><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Semantic Modelling</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">CQELS [<xref rid="B71-sensors-16-00600" ref-type="bibr">71</xref>]</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">RDF streams</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">SPARQL query response</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Continuous SPARQL query </td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">10 million triples</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Yes</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Dis</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Java</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Processing directly on Linked Stream Data</td></tr><tr><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Semantic Modelling</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">LSM [<xref rid="B27-sensors-16-00600" ref-type="bibr">27</xref>]</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">SSN ontology</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">SPARQL endpoint/HTTP REST</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">CQELS</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">70,000 sensor data sources</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Yes</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Cen</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Java/Virtuoso/Hadoop</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Integrated with XGSN [<xref rid="B26-sensors-16-00600" ref-type="bibr">26</xref>] in OpenIoT [<xref rid="B28-sensors-16-00600" ref-type="bibr">28</xref>]</td></tr><tr><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Semantic Modelling</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Q-ASSF [<xref rid="B72-sensors-16-00600" ref-type="bibr">72</xref>]</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">SSN ontology</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">SPARQL query response</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">CQELS</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">200 queries/3000 sensors/16,000 triples</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Yes</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Cen</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">RabbitMQ/Apache Jena</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Filtering algorithm to reduce sensor communications and triple transmission</td></tr><tr><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Semantic Modelling</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Linked Sensor Streams [<xref rid="B44-sensors-16-00600" ref-type="bibr">44</xref>]</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">RDF streams</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">SPARQL query response</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Type/Location based query (based on clustering)</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">20,000 stream data</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Yes</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Dis</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Java</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Combination of Linked Data and sensor streams</td></tr></tbody></table></table-wrap><table-wrap id="sensors-16-00600-t004" position="float"><object-id pub-id-type="pii">sensors-16-00600-t004_Table 4</object-id><label>Table 4</label><caption><p>Comparison of Search Techniques According to Content being Searched (Abbreviations are listed in the footer of <xref ref-type="table" rid="sensors-16-00600-t002">Table 2</xref>).</p></caption><table frame="hsides" rules="groups"><thead><tr><th align="center" valign="middle" style="border-top:solid thin;border-bottom:solid thin" rowspan="1" colspan="1">Classification</th><th align="center" valign="middle" style="border-top:solid thin;border-bottom:solid thin" rowspan="1" colspan="1">Search Technique</th><th align="center" valign="middle" style="border-top:solid thin;border-bottom:solid thin" rowspan="1" colspan="1">Data Format</th><th align="center" valign="middle" style="border-top:solid thin;border-bottom:solid thin" rowspan="1" colspan="1">Access Approach</th><th align="center" valign="middle" style="border-top:solid thin;border-bottom:solid thin" rowspan="1" colspan="1">Search Type</th><th align="center" valign="middle" style="border-top:solid thin;border-bottom:solid thin" rowspan="1" colspan="1">Scale of Experiments</th><th align="center" valign="middle" style="border-top:solid thin;border-bottom:solid thin" rowspan="1" colspan="1">D<sup>1</sup></th><th align="center" valign="middle" style="border-top:solid thin;border-bottom:solid thin" rowspan="1" colspan="1">Ar<sup>2</sup></th><th align="center" valign="middle" style="border-top:solid thin;border-bottom:solid thin" rowspan="1" colspan="1">Implementation</th><th align="center" valign="middle" style="border-top:solid thin;border-bottom:solid thin" rowspan="1" colspan="1">Remarks</th></tr></thead><tbody><tr><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Instantaneous Data</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">LiveWeb [<xref rid="B33-sensors-16-00600" ref-type="bibr">33</xref>]</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Sensor data in XML</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">HTML/AJAX</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Real-time content search based on keywords, category, and value range </td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">-</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Yes</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Cen</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">PHP/Java/Apache/MySQL</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Practical implementation without evaluation Should fit in global scale</td></tr><tr><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Instantaneous Data</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">SensorMap [<xref rid="B39-sensors-16-00600" ref-type="bibr">39</xref>]</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Direct communication with web accessible sensors</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Web services APIs</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Spatial search (based on COLR-tree/crawling)</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">-</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">-</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Cen</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">MSRSense toolkit</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">SenseWeb-based application, currently not accessible </td></tr><tr><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Instantaneous Data</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">GeoCENS [<xref rid="B40-sensors-16-00600" ref-type="bibr">40</xref>]</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">OGC SOS, SensorML, OGC O&M</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">SWE services</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Spatial search (Peano space filling curves)</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">~40,000 sensors/procedures</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Yes</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">P2P</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">-</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Designed for sensor data from smaller organizations or individuals</td></tr><tr><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Instantaneous Data</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">CQELS [<xref rid="B71-sensors-16-00600" ref-type="bibr">71</xref>]</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">RDF streams</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">SPARQL query response</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Continuous SPARQL query </td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">10 million triples</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Yes</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Dis</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Java</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Processing performed directly on Linked Stream Data</td></tr><tr><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Instantaneous Data <break></break>Historical Data</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">IoT-SVKSearch [<xref rid="B37-sensors-16-00600" ref-type="bibr">37</xref>]</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Sampling values with metadata in Raw Data Store</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Data in built-in format</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Keyword-based (B<sup>+</sup>-tree), spatial-temporal (R-tree), value-based (B<sup>+</sup>-tree) search</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">140,800~352,000 sensors</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Yes</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Dec</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">PostgreSQL/file system</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Multiple search functionalities supported</td></tr><tr><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Instantaneous Data Historical Data</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">FUTS Data Query [<xref rid="B42-sensors-16-00600" ref-type="bibr">42</xref>]</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Virtual Object ontology in OWL-DL</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">SenML/JSON</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Spatial search with time window/sensor type</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">20,000 sensors</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Yes</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Cen</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Java</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Cloud database for huge data storage</td></tr><tr><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Historical Data</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">LSM [<xref rid="B27-sensors-16-00600" ref-type="bibr">27</xref>]</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">SSN ontology</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">SPARQL endpoint/HTTP REST</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">CQELS</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">70,000 sensor data sources</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Yes</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Cen</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Java/OpenLink Virtuoso/Apache Hadoop</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Integrated with XGSN [<xref rid="B26-sensors-16-00600" ref-type="bibr">26</xref>] in OpenIoT [<xref rid="B28-sensors-16-00600" ref-type="bibr">28</xref>]</td></tr><tr><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Context-based Sensor</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">OSIRIS [<xref rid="B38-sensors-16-00600" ref-type="bibr">38</xref>]</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">OGC SWE Sensor model and data model</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">SWE services</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Spatial, temporal and keyword-based search</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">-</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Yes</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Cen</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">JSI/Apache Lucene</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Applications in Smart City domain, <break></break>Website of the project no longer accessible</td></tr><tr><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Context-based Sensor</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Microsearch [<xref rid="B31-sensors-16-00600" ref-type="bibr">31</xref>] <break></break>Snoogle [<xref rid="B32-sensors-16-00600" ref-type="bibr">32</xref>]</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Direct communication with sensor motes with built-in metadata </td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Virtual sensors in built-in format</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Keyword-based top-k search</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">-</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Yes</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Dis</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">TelosB motes</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Early search implementations with limited functionalities and limited scalability</td></tr><tr><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Context-based Sensor</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Linked Sensor Data [<xref rid="B53-sensors-16-00600" ref-type="bibr">53</xref>]</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">RDF</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">HTML/XML</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">SPARQL query</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">20,000 weather stations</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Yes</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Cen</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">OpenLink Virtuoso</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Combination of Linked Data, sensors and sensor data</td></tr><tr><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Context-based Sensor</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">SemSOS [<xref rid="B56-sensors-16-00600" ref-type="bibr">56</xref>]</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">SWE based model in Linked Data</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">OGC SWE SOS</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Named location based query</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">20,000 weather stations </td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">No</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Cen</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">RDF2Go/Sesame</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Mobile sensors are ignored</td></tr><tr><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Context-based Sensor</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">CASSARAM [<xref rid="B73-sensors-16-00600" ref-type="bibr">73</xref>]</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">SSN ontology</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">SPARQL query response</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">SPARQL query</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">1,000,000 sensors</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Yes</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Dis</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Apache Jena API</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Multiple sensor feature support <break></break>Fast top-k sensor selection</td></tr><tr><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Context-based Sensor</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">VCS [<xref rid="B74-sensors-16-00600" ref-type="bibr">74</xref>]</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Server nodes (objects)</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">List of nodes</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Keyword-based query with multiple features</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">-</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Yes</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">P2P</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">-</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">No evaluation provided</td></tr><tr><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Context-based Sensor</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">OpenIoT [<xref rid="B28-sensors-16-00600" ref-type="bibr">28</xref>]</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">SSN ontology</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">SPARQL endpoint/HTTP REST</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Continuous SPARQL query/Publish and Subscribe model</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">-</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Yes</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Dis</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">XGSN/LSM</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Multiple practical applications provided</td></tr><tr><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Context-based Sensor <break></break>Context-based Entity</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">SPITFIRE [<xref rid="B75-sensors-16-00600" ref-type="bibr">75</xref>]</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Sensor (RDF triple)</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">SPARQL query response</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">CQELS</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">40 physical sensors</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Yes</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Cen</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Jena Semantic Web Framework</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Semantic sensor descriptions</td></tr><tr><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Content-based Sensor</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Fuzzy-based Sensor Search [<xref rid="B76-sensors-16-00600" ref-type="bibr">76</xref>]</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Sensor data streams</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">-</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Sensor data stream based search for sensors</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">1500 data points/day</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Yes</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Dis</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Java</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Ranking based on sensor data prediction</td></tr><tr><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Content-based Sensor <break></break>Content-based Entity</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Dyser [<xref rid="B30-sensors-16-00600" ref-type="bibr">30</xref>]</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Virtual sensors (microformat)</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">URL/HTTP/HTML</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Keyword-based/value-based</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">385 sensors over 5 months</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Yes</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Cen</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Java/PHP</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Query of state of real world objects <break></break>Computation required for state awareness, the scale is limited to small number of sensors</td></tr><tr><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Content-based Sensor <break></break>Content-based Entity</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Sensor Ranking [<xref rid="B77-sensors-16-00600" ref-type="bibr">77</xref>]</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Sensor with outputs in built-in format</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Ranked list of sensors</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Prediction based ranking for content-based sensor search</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">20 sensors</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Yes</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Cen</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">C++</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Local scale deployment</td></tr><tr><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Context-based Entity</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Gander [<xref rid="B78-sensors-16-00600" ref-type="bibr">78</xref>]</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Nodes (objects) (tuple space/tuple graph)</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">HTTP REST</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Multi-hop query</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">20,000 mobile visitors</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Yes</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">P2P</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Java</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Mobile applications for smart university</td></tr><tr><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Context-based Entity</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">ISE [<xref rid="B79-sensors-16-00600" ref-type="bibr">79</xref>]</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Encrypted RFID records</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">XML/HTML/JSON</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Database-based query</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">1,000,000 RFID records</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Yes</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Dis</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Nginx/Tokyo Cabinet/C++</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Cryptography for security</td></tr><tr><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Content-based Entity</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Correlation-based Sensor Search [<xref rid="B80-sensors-16-00600" ref-type="bibr">80</xref>]</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Sensor with sensor data in built-in format</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">List of sensors</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Sensor search with a given state/output</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">384 sensors</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Yes</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Cen</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Java/SMILE reasoning engine</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Based on sensor data correlation</td></tr><tr><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Context-based Entity</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">DiscoWoT [<xref rid="B81-sensors-16-00600" ref-type="bibr">81</xref>]</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Built-in description for resources (objects)</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">JSON/XML</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">RESTful interface search</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">-</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Yes</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">Cen</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">AutoWoT toolkit</td><td align="center" valign="middle" style="border-bottom:solid thin" rowspan="1" colspan="1">No evaluation provided</td></tr></tbody></table></table-wrap></floats-group></pmc><affiliations><list></list><tree><noCountry><name sortKey="De, Suparna" sort="De, Suparna" uniqKey="De S" first="Suparna" last="De">Suparna De</name><name sortKey="Moessner, Klaus" sort="Moessner, Klaus" uniqKey="Moessner K" first="Klaus" last="Moessner">Klaus Moessner</name><name sortKey="Wang, Wei" sort="Wang, Wei" uniqKey="Wang W" first="Wei" last="Wang">Wei Wang</name><name sortKey="Zhou, Yuchao" sort="Zhou, Yuchao" uniqKey="Zhou Y" first="Yuchao" last="Zhou">Yuchao Zhou</name></noCountry></tree></affiliations></record>Pour manipuler ce document sous Unix (Dilib)
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