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Re: RDF primer text for 5.15: RDF mapping

From: David Booth <dbooth@w3.org>
Date: Thu, 31 Mar 2005 11:23:28 -0500
To: Jacek Kopecky <jacek.kopecky@deri.org>
Cc: WS-Description WG <www-ws-desc@w3.org>
Message-Id: <1112286208.22443.7975.camel@nc6000.w3.org>


Thanks for the draft.  I'll edit for style, add some higher level
context, and put it in the primer.  

On Thu, 2005-03-24 at 11:27, Jacek Kopecky wrote:
> Hi all, 
> below is a first cut of the text for primer section 5.15 - Mapping to
> RDF and Semantic Web, created by me and Bijan.
> Jacek
> 5.15 Mapping to RDF and Semantic Web
> WSDL is a language designed primarily with XML syntax. While XML is
> almost universally understood, it has several issues: 
>       * Composing two XML files into one depends on the languages: we
>         can be able to merge two WSDL files with the same
>         targetNamespace into one (as long as there are no conflicts),
>         but WSDL doesn't provide for composing two different documents
>         in different namespaces into a single XML document. 
>       * Extending XML languages with other XML languages depends on
>         the languages again. WSDL is extremely extensible, but the
>         meaning of every single extension in WSDL has to be defined -
>         putting a piece of XMI (XML format for UML) as extension in
>         WSDL may have different meaning from putting XMI into an XHTML
>         document. Therefore XML-based extensibility has very high cost
>         if many languages are involved. 
>       * Similarly, extending another XML language with pieces of WSDL,
>         while possible, has to be defined for all the possible
>         destinations. Putting a WSDL interface element into a UDDI
>         registry may mean a different thing from putting that
>         interface element into an XHTML document. 
>       * Finally, the meaning of pieces of WSDL is undefined by the
>         WSDL specification; while an interface element can form a
>         single XML document, it is not a WSDL document and the meaning
>         of such an element is largely undefined. 
> Application that require such levels of composability (or
> decomposability) are increasingly being based on RDF, a graph-based
> knowledge representation language, and Web Ontology Language (OWL),
> which can be thought of as an advanced schema language for RDF. The
> Semantic Web is envisioned as an interlinked collection of such
> applications, together working on the whole scale of the World Wide
> Web. 
> The document WSDL 2.0: Mapping to RDF describes how WSDL constructs
> are expressed in RDF using classes of resources (described with an
> ontology expressed in OWL) and assertions over individual resources.
> Effectively, a WSDL document represented in RDF can be easier extended
> with arbitrary RDF assertions and the WSDL information can easier be
> ascribed to arbitrary other knowledge. 
> 5.15.1 RDF representation of WSDL
> As RDF represents knowledge using resources and relationships between
> them, we need to turn WSDL concepts into this model. 
>      1. First, all components in WSDL (like Interfaces, Operations,
>         Bindings, Services, Endpoints etc., including extensions) are
>         turned into resources identified with the appropriate URIs
>         created according to Appendix C. 
>      2. Further things are represented as resources: 
>              1. Element declarations gathered from XML Schema (or
>                 similarly, other components from other type systems) 
>              2. Message content models 
>              3. Message exchange patterns (the URI identifying the MEP
>                 is the URI of the resource) 
>              4. Operation styles (similarly to MEPs, the URI of an
>                 operation style is the URI of the resource) 
>      3. All the resources above are given the appropriate types using
>         rdf:type stataments (an interface will belong to the class
>         Interface and an operation within an interface will belong to
>         the class InterfaceOperation, for example) 
>      4. All relationships in WSDL (like Operation belonging to an
>         Interface and having a given operation style) are turned into
>         RDF statements using the appropriate properties (here,
>         operation and operationStyle) 
> todo: as an example, an RDF translation of a (snippet of a) simple
> WSDL file from earlier in the primer 

David Booth
W3C Fellow / Hewlett-Packard
Received on Thursday, 31 March 2005 16:33:14 UTC

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