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Re: ISSUE 5.6 - daml:imports as magic syntax

From: Jeff Heflin <heflin@cse.lehigh.edu>
Date: Wed, 11 Sep 2002 17:26:59 -0400
Message-ID: <3D7FB523.643B6B5F@cse.lehigh.edu>
To: "Smith, Michael K" <michael.smith@eds.com>
CC: www-webont-wg@w3.org

Mike,

Your XML:Base solution certainly get around the relative URI problem.
But I'm not sure why you don't think it handles the <ontology about="">
problem. That's just another relative URI. However, there is still a
problem:

I don't think the embedded rdf:RDF tags are legal RDF. In RDFM&S Section
2.2.1 it seems that rdf:RDF should only appear at the top-level of a
document. If it is legal, then it would be interpreted as a property of
an Ontology, which doesn't seem right.

Jeff



"Smith, Michael K" wrote:
> 
> Here is what I think is a simple suggestion for an essentially
> syntactic treatment of owl:imports using XML:Base.
> 
> I wrote this note and then finally followed Jonathan's pointer to
> XInclude, which seems like a decent option, except for the requirement
> that a loop be a fatal error.  In distributed ontologies I would
> expect loops to show up.  ???
> 
> As I understand our current draft status, the structure of an OWL
> ontology with an imports clause is,
> 
> <rdf:rdf
>     xmlns     ="#"
>     ... plus other namespace declarations >
>  <owl:ontology about="">
>   ...
>   <owl:imports rdf:resource="http://www.w3.org/foo.owl" />
>   ...
>  </owl:ontology>
> </rdf:rdf>
> 
> (No comment on how odd the RDF:RDF wrapper around all OWL ontologies
> seems.)
> 
> If we consider textually replacing the imports clause with the text of
> the referenced ontology we would get something like:
> 
> <rdf:rdf
>     xmlns     ="#" >
>  <owl:ontology about="">
>   ...
>   <rdf:rdf
>       xmlns     ="#" >
>    <owl:ontology about="">
>     ...
>    </owl:ontology>
>   </rdf:rdf>
>   ...
>  </owl:ontology>
> </rdf:rdf>
> 
> Which has obvious problems, in both the imbedded namespace declaration
> and the imbedded 'about' attribute.
> 
> It would seem that we could solve this using XML:BASE.  Suppose the
> expansion augmented the imported ontology with a base expression that
> referenced the imported document.
> 
> <rdf:rdf
>     xmlns     ="#" >
>  <owl:ontology about="">
>   ...
>   <rdf:rdf
>       xml:base= "http://www.w3.org/foo.owl"
>       xmlns     ="#" >
>    <owl:ontology about="">
>     ...
>    </owl:ontology>
>   </rdf:rdf>
>   ...
>  </owl:ontology>
> </rdf:rdf>
> 
> This should actually work for the namespace component, since the scope
> of the xml:base occurence starts with the rdf:rdf element, and will
> extend until a new base is established or we exit the scope of the
> rdf:rdf tag. (See http://www.w3.org/TR/xmlbase/)
> 
> So, the remaining problem is the imbedded 'about' attribute.  Since we
> get to define what this attribute means, I would think we could define it
> relative to the current base URI.
> 
> Note that this works in the case of multiple, imbedded imports.
> 
> - Mike
> 
> Michael K. Smith, Ph.D., P.E.
> EDS - Austin Innovation Centre
> 98 San Jacinto, #500
> Austin, TX  78701
> 
> * phone: +01-512-404-6683
> * mailto:michael.smith@eds.com
> 
> -----Original Message-----
> From: Dan Connolly [mailto:connolly@w3.org]
> Sent: Tuesday, September 10, 2002 11:28 AM
> To: Jonathan Borden
> Cc: Jeff Heflin; Peter F. "Patel-Schneider; www-webont-wg@w3.org
> Subject: Re: ISSUE 5.6 - daml:imports as magic syntax
> 
> On Mon, 2002-09-09 at 19:40, Jonathan Borden wrote:
> >
> > Peter F. Patel-Schneider wrote:
> > >
> > > A treatment of imports can be done completely syntactically, by
> replacing
> > > imports foo, where foo is a URI (or whatever) by the contents of the
> > > document pointed at by foo.   This is the way I would handle it in the
> > > abstract syntax and direct semantics.
> >
> > hmmm... if we consider that daml:imports is syntactic sugar for XInclude
> > http://www.w3.org/TR/xinclude/ i.e.
> >
> > <xi:include
> >     xmlns:xi="http://www.w3.org/2001/XInclude"
> >     href="foo.daml"
> > />
> >
> > just using XInclude as it is already specified would allow us to prune
> this
> > whole discussion and the issues it raises of special syntax, semantics
> etc.
> 
> Not a bad idea...
> 
> XInclude wouldn't come for free (the RDF/XML spec doesn't say that
> RDF parsers must grok XInclude) but if we're interested in special
> syntax for syntactic inclusion, I'd prefer XInclude syntax, which
> is designed for exactly that purpose, rather than daml:imports,
> which sorta looks like an RDF property but it's sorta unclear
> how to specify that it acts like one.
> 
> --
> Dan Connolly, W3C http://www.w3.org/People/Connolly/
Received on Wednesday, 11 September 2002 17:27:02 GMT

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