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-harry
Harry Halpin, University of Edinburgh
http://www.ibiblio.org/hhalpin 6B522426
Forwarded message 1
Congrats on getting SAWSDL to Candidate Recommendation. I'm Harry
Halpin, Chair of the GRDDL WG [1] which links XML and XHTML (including
"microformats") to the Semantic Web in order to facilitate the
deployment of the Semantic Web. I have a news posting and a few
comments. There was an action for WG member Fabien to determine the
relationship between GRDDL and SAWSDL these to you earlier, but due to
his travelling I will attempt to articulate these.
In order to prevent a "surprise" Last Call, I'd like for your WG to
know that we are going to go, barring any final comments or problems,
to request move to Last Call on or shortly after Feb 15th for the
following three documents:
1) GRDDL Specification [2]
2) GRDDL Primer [3]
3) GRDDL Use Cases [4]
We believe this technology is related to the SAWSDL WG as a GRDDL can
be considered a type of function or "process" from XML to RDF, and after
reading the latest version of SAWSDL I believe there is a definite and
interesting relationship to SAWSDL [5]. First, according to my reading
of [5], ""liftingSchemaMapping and loweringSchemaMapping, that are
added to XML Schema element declarations, complex type definitions and
simple type definitions for specifying mappings between semantic data
and XML." In essence, a GRDDL is a way for a "lifting". However, there
are three differences:
1) "lifting" as you define it maps to a "semantic model", which "does
not rely on any particular semantic modeling language. It only requires
that the semantic concepts defined in it be identifiable via URI
references." In this regard, GRDDL is a subset of "lifting," as it
defines its output to a RDF graph, a subset of all "semantic models".
2) GRDDL applies to XML documents in general, including XHTML and XML
Schema. Insofar as "lifting" as defined in SAWSDL by
"liftingSchemaMapping" refers to XML Schema, GRDDL is a superset of
"lifting".
3) Lastly and most importantly, SAWSDL specifIes a way of specifying the
mapping that is componentized to the types of the XML Schema, while
GRDDL currently only operates over the whole XML document, and so cannot
at this time specify transformations at the level of simple and complex
XML Schema types.
I think these observatons require no changes to SAWSDL as the spec
stands. However, it would be nice to put in a reference to GRDDL, such
as after the sentence: "Other languages, such as XQuery can also be
used." "GRDDL (Gleaning Resource Descriptions from Dialects of Language)
is a way of "lifting" XML documents, including XML Schema, to RDF.
Transformations created for use by GRDDL can be used as lifting mappings
for SAWSDL if appropriate."
In other words, nothing new should be implemented, and the note merely
notices the relationship and that if someone makes a GRDDL transform for
an XML Schema to RDF someone can save effort and use the same transform
if wanted in a SAWSDL. I would also like to add a note about the
relationship to SAWSDL one of the GRDDL documents.
thanks!
[1] http://www.w3.org/2001/sw/grddl-wg/
[2] http://www.w3.org/2004/01/rdxh/spec
[3] http://www.w3.org/2001/sw/grddl-wg/doc29/primer.html
[4] http://www.w3.org/2001/sw/grddl-wg/doc43/scenario-gallery.htm
[6] http://www.w3.org/TR/sawsdl/
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-harry
Harry Halpin, University of Edinburgh
http://www.ibiblio.org/hhalpin 6B522426