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Subject: RE: ebXML Representtion of Metadata

I note that you do not list XMI in your list of considerations, have you
looked at this?  XMI is the adopted OMG standard for representation of
metadata in XML.  There has already been some discussion of using XMI within
EbXml.  I am not as familiar with RDF and will take a look at it.

Cory Casanave
Data Access Technologies

> -----Original Message-----
> From:	Miller, Robert (GXS) [SMTP:Robert.Miller@gxs.ge.com]
> Sent:	Tuesday, May 23, 2000 2:40 PM
> To:	ebxml-core@lists.oasis-open.org; ebXML-Architecture List
> Subject:	ebXML Representtion of Metadata
> Representation of Metadata in ebXML
> This submission is a proposal by the author, Bob Miller, and has not been
> yet undergone review by the ebXML Project Teams.  As such, it has no
> official standing.
> The ebXML requirement for interoperability among both existing and future
> XML implementations imposes a functional requirement for the machine
> recognition of semantic and syntactic properties of XML elements which
> comprise compliant ebXML documents.  Such properties are commonly referred
> to as metadata.  
> XML 1.0 provides a basic capability for representing metadata via the use
> of
> attributes associated with XML elements.  The XML Schema work in progress
> in
> W3C provides a somewhat more sophisticated mechanism.  This work has not
> yet
> achieved the level of a W3C Recommendation.  The Resource Description
> Framework (RDF) Model and Syntax Specification, which has reached the W3C
> Candidate Recommendation level, is part of the W3C Metadata Activity, and
> it
> provides a broad capability for representing data objects.  It supports
> the
> concepts of object classes, superclasses, and subclasses, of common
> properties (including constraints) of such objects, and of extension to
> user
> defined properties of such objects.   
> Metadata defined in an RDF can be used to automatically generate an XML
> DTD,
> Schema, or other XML syntax useful in validating compliance of an XML
> document to defined properties of the elements comprising the document.
> Metadata defined in an RDF is itself representable in XML, and a concrete
> syntax for such representation is defined in the RDF specification.
> Upon careful review of the XML DTD, XML Schema, and RDF specifications, I
> conclude that the RDF specification is most capable of representing the
> metadata properties of Core Components and other business data objects
> defined by the ebXML specifications.    
> To support this recommendation, I propose the following condition be
> satisfied for any document which claims ebXML compliance:
> 				Compliance to ebXML specifications requires
> that each XML element that appears in an XML document asserting ebXML
> compliance shall: 
> *	provide a pointer, either as an explicit attribute definition in the
> XML element usage instance or by prior reference to a default attribute
> definition for the XML element to an RDF/XML representation of metadata
> associated with the XML element
> *	define in each referenced RDF at least such minimal properties as
> may be specified as required for compliance by the ebXML specifications.
> The ebXML specification shall define a well known attribute name within a
> namespace defined by the ebXML specification, to contain the pointer to
> the
> RDF metadata.  The ebXML specifcation shall also specify the names of
> properties, in such namespaces as appropriate, which are to be used to
> define specific metadata properties required or optional in the ebXML
> specification.  Additional properties not defined by the ebXML
> specification
> may be provided in namespaces not defined by ebXML.  Such additional
> properties shall be outside the scope of the ebXML specification 
> I suggest that the attribute name chosen to represent this pointer be
> named 
> 	'RDF'
> prefaced of course by the namespace qualifier that identifies the ebXML
> namespace.  
> A key feature of this design is the storage of metadata associated with
> business objects and core components in a common format approved by the
> W3C
> as a Candidate Recommendation, accessible as needed via a pointer
> mechanism
> associated with the individual XML elements which comprise a document.
> For
> an existing XML document defined without knowledge of ebXML requirements,
> conformance to ebXML can be achieved through simple enrichment of the DTD
> (or Schema) used to define the document.
> Also, minimal overhead is imposed on the processing of an ebXML document
> when there is no business need to dynamically traverse the associated
> metadata. In the normal case of repetitive use of a common business
> document, traversal of the metadata would likely be a one-time activity
> used
> to establish mappings between the business application and the document
> content.  Similarly, construction of a Schema to provide partial
> validation
> of document content would be a one-time activity.  The choice to apply
> Schema validation to incoming or outgoing documents during testing and
> during live production is left to user discretion.
> In my opinion, the ebXML Core Components should assume responsibility for
> specifying the required and optional ebXML RDF properties for use both in
> the definition of Core Components and in the definition of other data
> objects required to define an ebXML compliant document.  
> The RDF specification is syntax neutral, and so meets the requirement that
> Core Components work output should be syntax neutral.  Since a concrete
> representation of RDF in XML also exists, there appears to be no need for
> the Registry and Repository team to address the representation of the
> output
> of the Core Component team in XML syntax.  There may remain a need for the
> Registry and Repository team to cooperate with the Business Process and
> Core
> Component teams to define the RDF representation of the output of the
> Business Process team. 
> Cheers,
>              Bob 

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