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		<p><a href="http://www.w3.org/"><img src="http://www.w3.org/Icons/w3c_home" alt="W3C" height="48" width="72" /></a><a href="http://www.w3.org/2005/Incubator/XGR/"><img height="48" width="160" alt="W3C Incubator Report" src="http://www.w3.org/2005/Incubator/images/XGR" /></a></p>

<h1><a name="title" id="title"></a>W3C RDB2RDF Incubator Group Report</h1>

<h2><a name="w3c-doctype" id="w3c-doctype"></a>W3C Incubator Group Report 26 January 2009</h2>
<dl>
	<dt>
		This version:
	</dt>
	<dd>
		<a href="http://www.w3.org/2005/Incubator/rdb2rdf/XGR-rdb2rdf-20090126/">http://www.w3.org/2005/Incubator/rdb2rdf/XGR-rdb2rdf-20090126/</a>
	</dd>
	<dt>
		Latest version:
	</dt>
	<dd>
		<a href="http://www.w3.org/2005/Incubator/rdb2rdf/XGR-rdb2rdf/">http://www.w3.org/2005/Incubator/rdb2rdf/XGR-rdb2rdf/</a>
	</dd>
	<dt>
		Previous version:
	</dt>
	<dd>
		This is the first public version
	</dd>
	<dt>
		Editor:
	</dt>
	<dd>
		Ashok Malhotra, Oracle
	</dd>
</dl>

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<h2><a name="abstract" id="abstract"></a>Abstract</h2>
<p>This is the final report from the RDB2RDF XG.
 The XG recommends that the W3C initiate a WG to standardize a language for
 mapping Relational Database schemas into RDF and OWL. </p>

<h2><a id="status" name="status">Status of This Document</a></h2>
<p><em>This section describes the status of this document at the time of its publication. Other documents may supersede this document. A list of <a href="/2005/Incubator/XGR/">Final Incubator Group Reports</a> is available. See also the <a href="http://www.w3.org/TR/">W3C technical reports index</a> at http://www.w3.org/TR/.</em></p>

<p>Publication of this document by W3C as part of the <a href="http://www.w3.org/2005/Incubator/">W3C Incubator Activity</a> indicates no endorsement of its content by W3C, nor that W3C has, is, or will be allocating any resources to the issues addressed by it. Participation in Incubator Groups and publication of Incubator Group Reports at the W3C site are benefits of <a href="http://www.w3.org/Consortium/join">W3C Membership</a>.</p>

<p>Incubator Groups have as a <a href="http://www.w3.org/2005/Incubator/procedures.html#Patent">goal</a> to produce work that can be implemented on a Royalty Free basis, as defined in the W3C Patent Policy. Participants in this Incubator Group have made no statements about whether they will offer licenses according to the <a href="http://www.w3.org/Consortium/Patent-Policy-20030520.html#sec-Requirements">licensing requirements of the W3C Patent Policy</a> for portions of this Incubator Group Report that are subsequently incorporated in a W3C Recommendation.</p>

<p>This is the final recommendation from the RDB2RDF XG.</p>


<div class="toc">
<h2 class="notoc">
    <a id="contents" name="contents">Table of Contents</a>
   </h2>

   <ul id="toc" class="toc">
    <li class="tocline"><a href="#recommendation"><b>1. Recommendation</b></a>
		<ul class="toc">
    		<li class="tocline"><a href="#usecases"><b>1.1 Use Cases</b></a>
     			<ul class="toc">
      				<li class="tocline"><a href="#biomedical">1.1.1 Integrating Databases to Research Nicotine Dependency</a></li>
      				<li class="tocline"><a href="#triplify">1.1.2 Triplify: Exposing Relational Data on the Web</a></li>
      				<li class="tocline"><a href="#enterprise">1.1.3 Integration of Enterprise Information Systems</a></li>
      				<li class="tocline"><a href="#ordnance">1.1.4 Ordnance Survey Use Case</a></li>
				</ul>
			</li>
			<li class="tocline"><a href="#liaisons"><b>1.2 Liaisons</b></a></li>
			<li class="tocline"><a href="#startingpoints"><b>1.3 Starting Points</b></a></li>
    	</ul>
	</li>
	<li class="tocline"><a href="#references"><b>References</b></a></li>
    <li class="tocline"><a href="#acknowledgments"><b>Acknowledgments</b></a></li>
   </ul>
</div>

<hr /><div class="body"><div class="div1">
<h2><a name="recommendation" id="recommendation"></a>1 Recommendation</h2><p>
 The RDB2RDF XG recommends that the W3C initiate a Working Group (WG) to
 standardize a language for mapping Relational Database schemas into RDF and
 OWL.  Such a standard will enable the vast amounts of data stored in
 Relational databases to be published easily and conveniently on the Web.  It
 will also facilitate integrating data from separate Relational databases and
 adding semantics to Relational data.</p><p>This recommendation is based on the a survey of the State Of the Art
 conducted by the XG <a href="#StateOfArt">[StateOfArt]</a> as well as the usecases
 discussed below.</p><p>The mapping language defined by the WG would facilitate the development of
 several types of products.  It could be used to translate Relational data into
 RDF which could be stored in a triple store.  This is sometimes called
 Extract-Transform-Load (ETL).
 Or it could be used to generate a virtual mapping that could be queried using
 SPARQL and the SPARQL translated to SQL queries on the underlying Relational
 data.  Other products could be layered on top of these capabilities to query
 and deliver data in different ways as well as to integrate the data with other
 kinds of information on the Semantic Web.</p><p>The mapping language should be complete regarding when compared to to the
 relational algebra.  It should have a human-readable syntax as well as XML and
 RDF representations of the syntax for purposes of discovery and machine
 generation.</p><p>There is a strong suggestion that the mapping language be expressed in
 rules as defined by the W3C <a href="#RIF">[RIF]</a> WG. The syntax does not have
 to follow the RIF syntax but should a round-trippable mapping
 between mapping language and a RIF dialect.
 The output of the mapping should be defined in terms of an RDFS/OWL
 schema.</p><p>
 It should be possible to subset the language for simple applications such as
 Web 2.0. This feature of the language will be validated by creating a library
 of mappings for widely used apps such as Drupal, Wordpress, phpBB.</p><p>
 The mapping language will allow customization with regard to names and data
 transformation.  In addition, the language must be able to expose vendor
 specific SQL features such as full-text and spatial support and vendor-defined
 datatypes.</p><p>
 The final language specification should include guidance with regard to
 mapping Relational data to a subset of OWL such as OWL/QL or OWL/RL.</p><p>
 The language must allow for a mechanism to create identifiers for database
 entities. The generation of identifiers should be designed to support the
 implementation of the linked data principles <a href="#LinkedData">[LinkedData]</a>. Where
 possible, the language will encourage the reuse of public identifiers for
 long-lived entities such as persons, corporations, geo-locations, etc.  See
 <a href="#liaisons"><b>1.2 Liaisons</b></a>.</p><p>
 The proposed Working Group will also create a set of test cases that could be
 used to verify conformance.</p><div class="div2">
<h3><a name="usecases" id="usecases"></a>1.1 Usecases </h3><p>To bootstrap exploitation of the Web as a globally accessible linked
 database, we need a few essentials:</p><ul><li>Web accessible data needs to increase in granularity and cross
 linkage.</li><li>Web applications and solutions must produce structured interlinked data as
 extensions of existing functionality.</li><li>Web users must be shielded from the underlying complexity of injecting
 structured linked data into the Web.</li></ul><div class="div3">
<h4><a name="biomedical" id="biomedical"></a>1.1.1 Integrating Databases to Research Nicotine Dependency</h4><p>
 Complex biological queries generally require the integration of information
 from several sources. To understand the genetic basis of nicotine dependence,
 gene and pathway information needed to be integrated and three complex
 biological queries answered using the integrated knowledge base.   The gene
 information source NCBI Entrez Gene, which has gene-related records of ~2
 million genes needed to be integrated with pathway information sources, such
 as KEGG (Kyoto Encyclopedia for Genes and Genomics). Comparing results across
 model organisms required homology information provided by the NCBI HomoloGene,
 containing homology data for several completely sequenced eukaryotic
 organisms).</p><p>
 An ontology-driven approach was used to integrate the two gene resources
 (Entrez Gene and HomoloGene) and the three pathway resources (KEGG, Reactome
 and BioCyc). An OWL ontology called the Entrez Knowledge Model (EKoM) was
 created for the gene resources and integrated with the extant BioPAX ontology
 designed for pathway resources. The integrated schema was populated with data
 from the pathway resources, publicly available in BioPAX-compatible format,
 and gene resources for which a population procedure was created.
 </p><p>
 SPARQL was used to formulate queries to investigate the genetic basis of
 nicotine dependence over the integrated knowledge base:</p>
<ul>
	<li>Which genes participate in a large number of pathways?
	</li>
	<li>Identify "hub genes" from the perspective of gene interaction?
	</li>
	<li>Which genes are expressed in the brain, in the context of neurobiology of nicotine dependence and various neurotransmitters in the central nervous system?
	</li>
</ul>
<p>
 The result was very successful.  The queries could easily identify hub genes,
 i.e., those genes whose gene products participate in many pathways or interact
 with many other gene products. See
 <a href="#NicoteneDependence">[NicotineDependence]</a> for details.</p>

</div>

<div class="div3">
<h4><a name="triplify" id="triplify"></a>1.1.2 Triplify: Exposing Relational Data on the Web</h4>
<p>In order to make the Semantic Web useful to ordinary Web users, RDF and OWL
 have to be deployed on the Web on a much larger scale. Web applications such
 as Content Management Systems, online shops or community applications (e.g.
 Wikis, Blogs, Fora) already store their data in relational databases <a href="#triplifypaper">[triplifypaper]</a>. Providing a standardized way to map the relational data
 structures behind these Web applications into RDF, RDF-Schema and OWL will
 facilitate broad penetration and enrich the Web with RDF data and ontologies
 and facilitate novel semantic browsing and search applications.</p><p>By supporting the long tail of Web applications and thus counteracting the
 centralization of the Web 2.0 applications the planned RDB2RDF standardization
 will help to give control over data back to end-users and thus promote a
 democratization of the Web.</p><p>To support this usecase scenario, the mapping language should be easily
 implementable for lightweight Web applications and have a shallow learning
 curve to foster early adoption by Web developers.</p></div><div class="div3">
<h4><a name="enterprise" id="enterprise"></a>1.1.3 Integration of Enterprise Information Systems</h4><p>
 Efficient information and data exchange between application systems within and
 across enterprises is of paramount importance in the increasingly networked
 and IT-dominated business atmosphere. Existing Enterprise Information Systems
 such as CRM, CMS and ERP systems use Relational database backends for
 persistence. RDF and Linked Data can provide data exchange and integration
 interfaces for such application systems, which are easy to implement and use,
 especially in settings where a loose and flexible coupling of the systems is
 required.</p><p>Insight can often be gained by integrating data from databses built for
 different purposes in separate corporate silos.  For example, integrating data
 from a bug database with a customer database may help understand ordering
 behavior as a function of the bugs encountered.</p><p>
 In Supply Chain Management (SCM), for example, it is vital to exchange product
 catalogs and other goods related information within a network of
 interconnected businesses involved in the ultimate provision of product and
 service packages. Such information is stored in relational databases and
 sometimes already exchanged electronically, but a variety of different
 technologies are used (e.g. proprietary files, XML files, DB dumps, Web
 Services etc.). Realizing a completely electronic information flow requires
 significant initial investments and currently limits the flexibility of
 businesses (e.g. with regard to changes in business partners). The envisioned
 RDB2RDF mapping language applied in conjunction with existing RDB based SCM
 systems will support the use of RDF and unique identifiers for realizing
 flexible information information flows accompanying supply chains.
 </p><p>
 The mapping language to be standardized by the proposed WG will simplify the
 publishing of enterprise data and information from Relational data backends
 and, thus, facilitate the interlinking and exchange of information between
 business information systems. In this scenario on-demand transformation of
 relational data to RDF, scalability and completeness with regard to the
 relational algebra are central requirements. </p></div>

<div class="div3">
<h4><a name="ordnance" id="ordnance"></a>1.1.4 Ordnance Survey Use Case</h4>
<p>
 Ordnance Survey, the National mapping agency of the UK, operates a very
 large geographical information system based on Oracle Spatial.
 The database contains topographical features, soil type and land use
 information.  All these types of information are independently
 maintained and use separate terminologies.  They describe the same land area
 but the boundaries of objects utilized for representing land
 use and soil type and topography do not coincide:  For example, a pasture
 might consist of two distinct types of soil.</p><p>An example of a need to integrate this information is modeling filtration
 of
 pollutants into water bodies from agricultural land. The soil
 type determines the degree of filtration, the land use determines the type
 of pollutant.  Topography determines whether
 the field is next to a water body.</p><p>An ontology exists for describing the types of objects in each database.
 The benefit from mapping the data to RDF is in simplifying querying and
 integration of the data.  The very high volume of data makes an ETL
 approach impracticable, besides, the Oracle Spatial database offers spatial
 joining which is generally not available on RDF stores.</p><p>
 Thus, it is necessary to take SPARQL queries expressed in terms of the land
 use, soil type and topography ontologies and convert them into
 single SQL statements, with all joining and filtering to take place at the
 relational database.  In the process, high level concepts need to be
 translated into SQL conditions on data that is not readily human readable.</p><p>
 Business questions to be answered by the use case are for example:</p><ul><li>What is the total length of river bank bordered by permeable soil used for
 grazing along a certain river?</li><li>What types of crops are being cultivated within 100m of water, with total
 land use grouped by crop.</li><li>What watter bodies are subject to high environmental load from
 agriculture, as defined by little current and extensive use of adjacent
 land.</li></ul><p>
 From the viewpoint of RDB to RDF mapping, this usecase highlights the need to
 integrate data from different databases, built for different purposes.  It
 also
 emphasizes need for extensibility in the mapping language for supporting RDBMS
 vendor
 specific features.  In the present case, Oracle expresses a spatial join
 using a special type of derived table not found
 in standard SQL, thus the customization need is deeper than just supporting
 calls to native SQL functions.</p><p>
 The inference requirement consists primarily of expanding class membership
 into and's and or's of conditions on the relational data.  In
 some cases, these conditions are spatial, such as bordering on or contained
 in.  The user should  be familiar with the ontologies but
 should not have to know about the classification codes used in the
 databases.
 </p></div>
</div>

<div class="div2">
<h3><a name="liaisons" id="liaisons"></a>1.2 Liaisons</h3>
<p>
 The WG must track the evolution of SPARQL and liaise with the DAWG WG as well
 as the OWL WG.  The proposed WG will also keep track of work on assigning
 unique identifiers to well-known entities such as the ENS system associated
 with the OKKAM project
 <a href="#okkam">[OKKAM]</a> and the Common Naming Project started by Neuro Commons
 <a href="#CommonNaming">[Common Naming Project]</a></p></div>

<div class="div2">
<h3><a name="startingpoints" id="startingpoints"></a>1.3 Starting Points</h3><p>
 The WG will take as its starting point the mapping languages developed by the
 <a href="#D2RQ">[D2RQ]</a> and <a href="#Virtuoso">[Virtuoso]</a> efforts.</p></div></div>

<div class="div1">
<h2><a name="references" id="references"></a>References</h2>

<dl><dt class="label"><a name="CommonNaming" id="CommonNaming"></a>Common Naming Project</dt><dd>
       <a href="http://neurocommons.org/page/Common_Naming_Project"><cite>Neuro Commons Common Naming Project
       </cite></a>, Science Commons, Sept 17, 2008.
        (See http://neurocommons.org/page/Common_Naming_Project.)</dd><dt class="label"><a name="D2RQ" id="D2RQ"></a>D2RQ</dt><dd>
       <a href="http://www4.wiwiss.fu-berlin.de/bizer/D2RQ/spec/"><cite> The D2RQ Platform v0.5.1, User Manual and Language
 Specification
       </cite></a>, Chris Bizer, Richard Cyganiak, Jorg Garbers, Oliver Maresch
        (See http://www4.wiwiss.fu-berlin.de/bizer/D2RQ/spec/.)</dd><dt class="label"><a name="RIF" id="RIF"></a>RIF</dt><dd>
            <a href="http://www.w3.org/2005/rules/wiki/RIF_Working_Group"><cite>W3C Rule Interchange Format Working Group</cite></a>
        (See http://www.w3.org/2005/rules/wiki/RIF_Working_Group.)</dd><dt class="label"><a name="LinkedData" id="LinkedData"></a>LinkedData</dt><dd>
            <a href="http://www.w3.org/DesignIssues/LinkedData.html"><cite>Design Issues for Linked Data</cite></a>, Tim Berners-Lee
        (See http://www.w3.org/DesignIssues/LinkedData.html.)</dd>

     <dt class="label"><a name="StateOfArt" id="StateOfArt"></a>StateOfTheArtSurvey</dt>
	  <dd><a href="http://www.w3.org/2005/Incubator/rdb2rdf/RDB2RDF_SurveyReport.pdf"><cite>Mapping Relational Data to RDF and OWL: A Literature
	        Survey</cite></a>, Satya Sahoo, Wolfgang Halb</dd>
		       <dt class="label"><a name="okkam" id="okkam"></a>OKKAM</dt><dd>
            <a href="http://www.okkam.org/"><cite>An Entity Name System (ENS)
 for the Semantic Web</cite></a>, Paolo Bouquet, Heiko Stoermer, Barbara
 Bazzanella, January 2008.
        (See http://www.okkam.org/.)</dd>
	<dt class="label"><a name="Virtuoso" id="Virtuoso"></a>Virtuoso</dt>
	<dd>
	     <a href="http://virtuoso.openlinksw.com"><cite>Virtuoso Meta Schema Language</cite></a> (See:
	     http://virtuoso.openlinksw.com/dataspace/dav/wiki/Main/VOSSQL2RDF)
	</dd>
	     <dt class="label"><a name="triplifypaper" id="triplifypaper"></a>Triplify
	     </dt><dd>
       <a href="http://www.informatik.uni-leipzig.de/~auer/publication/triplify.pdf"><cite>Triplify - Lightweight Linked Data Publication from Relational
 Databases, submitted to WWW 2009
       </cite></a>Auer, Dietzold, Lehmann, Hellmann, Aumueller
        (See http://www.informatik.uni-leipzig.de/~auer/publication/triplify.pdf.)</dd><dt class="label"><a name="NicoteneDependence" id="NicoteneDependence"></a>NicoteneDependence</dt><dd>
       <a href="http://dx.doi.org/10.1016/j.jbi.2008.02.006 "><cite>An ontology-driven semantic mashup of gene and biological
 pathway information: Application to the domain of nicotine dependence
       </cite></a>Satya S. Sahoo, Olivier Bodenreider, Joni L. Rutter, Karen J.
 Skinner and Amit P. Shetha       (See http://dx.doi.org/10.1016/j.jbi.2008.02.006 .)</dd></dl></div>

<h2>
   <a id="acknowledgments" name="acknowledgments">Acknowledgments</a>
  </h2>

  <p>
   The editor would like to thank the members of the RDB2RDF XG who have contributed to the ideas in this report.
   We would also like to thank the guests who have come and presented their work to the RDB2RDF XG.
  </p>
</div>
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