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DAML+OIL, RDF, XML & WebOnt

From: Jeremy Carroll <jjc@hplb.hpl.hp.com>
Date: Fri, 7 Dec 2001 11:20:54 -0000
To: <www-webont-wg@w3.org>
Message-ID: <JAEBJCLMIFLKLOJGMELDMEKDCCAA.jjc@hplb.hpl.hp.com>
Summary: DAML+OIL is built on RDF, not XML.

Conclusion from below:
[[[
DAML+OIL assumes full RDF processing with a compliant RDF parser.

A DAML ontology written in N3 or N-triple is still a DAML ontology.

This is in contrast with other RDF dialects such as RSS [7] or CC/PP [8]
where many implementations assume a rigid XML document format, with no
variation from the examples in the specs.
]]]


After the daml+oil walkthru walkthru I feel a need to articulate my
understanding of the relationship between DAML+OIL, RDF and XML.

This is either:
+ for the newbies to RDF for education
or
+ a proposal for how webont should be

depending on whether other people agree with me!


XML [1] is a general purpose mark-up language for making documents that are
both machine and human readable.

RDF [2] is a data description framework which gives a way of constructing
labelled directed graphs, and an understanding [3] of how these may be
interpreted as a description of something.
One possible serialization of an RDF graph is given in an XML form. There
are other possible serializations such as N3 [4] or N-Triple [5]. It is also
possible to have a graph which is not in a document and hence not serialized
(e.g. in memory somewhere). There are many alternative representations of
the same information in RDF/XML.

DAML+OIL uses RDF to describe ontologies. Hence, a possible serialization of
a DAML ontology is as an RDF/XML file.

In particular, there are many different RDF/XML files that correspond to the
same RDF graph. DAML+OIL places no restriction on which RDF/XML
serialization is used.
For example, it is legal to write a DAML+OIL ontology expanding the
daml:collection lists out in full.

For example the idiom

<daml:Ontology rdf:about="" />

does not have to appear first, and can use an absolute URI instead of the
relative URI ""; it can also use an rdf:Description node

<rdf:Description rdf:type="http://www.daml.org/2001/03/daml+oil#Ontology" />

or

<rdf:Description>
   <rdf:type rdf:resource="http://www.daml.org/2001/03/daml+oil#Ontology" />
</rdf:Description>

That is DAML+OIL assumes full RDF processing with a compliant RDF parser
such as ARP [6] (note my interest :) ).

Also a DAML ontology written in N3 or N-triple is still a DAML ontology.

This is in contrast with other RDF dialects such as RSS [7] or CC/PP [8]
where many implementations assume a rigid XML document format, with no
variation from the examples in the specs.

Jeremy

[1] "Extensible Markup Language (XML) 1.0", World Wide Web Consortium
Recommendation, 1998 http://www.w3.org/TR/1998/REC-xml-19980210

[2] "RDF Model & Syntax" W3C, 1999,
http://www.w3.org/TR/1999/REC-rdf-syntax-19990222/

[3] "RDF Model Theory" W3C Working Draft 2001 http://www.w3.org/TR/rdf-mt/

[4] "N3" hmm? Berners-Lee & Connolly

[5] "RDF Test Cases" W3C Working Draft 2001
http://www.w3.org/TR/rdf-testcases/

[6] "Another RDF parser", J Carroll, 2001,
http://www-uk.hpl.hp.com/people/jjc/arp

[7] "RDF Site Summary (RSS) 1.0", 2000, http://purl.org/rss/1.0/spec

[8] "Composite Capability/Preference Profiles (CC/PP): Structure and
Vocabularies" W3C Working Draft 2001 http://www.w3.org/TR/CCPP-struct-vocab/
Received on Friday, 7 December 2001 06:21:20 GMT

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