Introduction

XML data is one of the most common format of data being transformed into Linked Data. Therefore, the XSLT module is created to provide very fine-grained classes and properties to describe how data was created by applying XSLT transformation. Some of the OPMV Core Ontology classes and corresponding XSLT Module sub-classes include:

• Agent: Processor
• Artifact: Binding, Stylesheet, Template, MatchingTemplate, NamedTemplate
• Process: Transformation

The module also created its own class QName and reused concepts from existing vocabularies, including foaf:Agent and doap:Version.

It defines 8 object properties that extend the OPMV core and the OPMV Common Module:

• xslt:used, xslt:source and xslt:binding as sub-properties of common:usedData, which itself is the sub-property of opmv:used;
• xslt:initialTemplate, xslt:module and xslt:stylesheet as sub-properties of common:usedScript, which is another sub-property of opmv:used;
• xslt:wasResultOf as sub-property of opmv:wasGeneratedBy, to refer to the artifact generated by the XSLT transformation process;
• xslt:processor as sub-property of opmv:wasControlledBy, to refer to processor that performed the transformation process. The processor can be either a XSLT 1.0 processor or a XSLT 2.0 processor.

Besides, the XSLT module also defines the following stand-alone object properties, some of which are listed below:

• xslt:imports to refer to the stylesheet that imports another one;
• xslt:includes to refer to the stylesheet that includes another one;
• xslt:initialMode to refer to the initial mode used for a transformation;
• xslt:mode to refer to the mode, which is identified by a QName, associated with a template;
• xslt:name to express the qualified name of something in XSLT;
• xslt:name to express the qualified name of something in XSLT.

Additional object properties and data properties from the XSLT module can be found documented in details in its schema, made available at its namespace: http://purl.org/net/opmv/types/xslt#.

Example

Example: Data creation by data transformation with XSLT

In this use case an RDF graph is created to describe each region based on the NaPTAN/NPTG data. Because the whole NaPTAN/NPTG data is available as one big XML file, the developer uses a stylesheet to split it up into lots of little XML files. Each of these XML files contains information about one region and a number of administrative areas and a number of districts. Then the developer processed this bunch of XML files with an XSLT stylesheet. The XSLT creates a number of RDF documents, one per region, administrative area and district.

The first example triples below use terms from the OPMV core to describe how each RDF graph about a region is created by data transformations with XSLT. The second example shows how the same information can be more precisely expressed using the XSLT module.

### the rdf graph is generated by a transformation process that uses the processor _:saxon

</data/transport/nptg/2010-03-31/region/EA>
   a opmv:Artifact ;
   opmv:wasEncodedBy <nptg/2010-03-31/region/EA.rdf> ;
   opmv:wasGeneratedBy [
     a opmv:Process ;
     opmv:used _:regionData ;
     opmv:used _:transformation ;
     opmv:wasControlledBy   _:saxon ;
     opmv:wasControlledBy <http://www.jenitennison.com/#me> ;
   ] 
.


</data/transport/nptg/2010-03-31/region/EA.rdf>
   a foaf:Document , opmv:Artifact ;
   opmv:wasGeneratedBy [
     a opmv:Process ;
     opmv:used </source/transport/nptg/2010-03-31/region/region-1.xml> ;
     opmv:used </code/transport/nptg/2010-03-31/xsl/region.xsl> ;
     opmv:wasPerformedBy _:saxon ;  ### _:saxon is a software
     opmv:wasPerformedBy <http://www.jenitennison.com/#me> ;
   ] 
.

The example below shows how we can use the XSLT module to:

• differentiate the different roles played by the processor :saxon and agent :me in the transformation process
• express that the XML data is the source data and the XLST script is the script used as inputs to the transformation process.

</data/transport/nptg/2010-03-31/region/EA.rdf>
   a foaf:Document , opmv:Artifact ;
   xslt:wasResultOf [
     a xslt:Transformation ;
     xslt:source </source/transport/nptg/2010-03-31/region/region-1.xml> ;
     xslt:stylesheet </code/transport/nptg/2010-03-31/xsl/region.xsl> ;
     xslt:processor _:saxon ;  ### _:saxon is a software
     opmv:wasPerformedBy <http://www.jenitennison.com/#me> ;
   ] 
.