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Re: DAML+OIL: Questions & Improvements.

From: Dave Beckett <dave.beckett@bristol.ac.uk>
Date: Tue, 30 Jan 2001 11:35:16 +0000
To: www-rdf-logic@w3.org
Message-ID: <4352.980854516@tatooine.ilrt.bris.ac.uk>

I'll reply to this bit of the message since it seems like an
appropriate place to give my comments based on stuff I've been doing
with Redland[1] and Rapier[2].

>>>"King . Dany" said:
<snip/>
> Syntactically however, it is... mostly (discrepancies: 1. RDF is requires
> acyclic subclass relations, DAML+OIL allows cyclic subclass relations; 2.
> DAML+OIL requires one syntax for cardinality to avoid exposed content, thus
> other equivalent and legal RDF syntaxes are illegal for DAML+OIL
> cardinality; 3. RDF allows only one range restriction per property, DAML+OIL
> allows multiple; 4. the "daml:collection" doesn't exist in RDF).  Therefore,
> with such vast differences in semantics and a ever growing syntactic
> divergence, how can backward compatibility be an issue?
<snip/>


1. acyclic/cycle class relations/RDF Properties

I need to know which one to give optimise for.  I assert without
evidence that asking typing/classing questions will be very common
for RDF/RDFS systems and applications of them and they need to be
optimised and have good APIs.

2. cardinality
3. range/domain

Not proposing to do anything special for these at present.

4. daml:collection

When designing my Rapier[2] parser, I designed support for other
types of parseType and collections (class of things that include
rdf:Seq, rdf:Bag, rdf:Alt), assuming that some people would need this
since it is commonly agreed the current container stuff is horrible.
I haven't finished implementing this support yet.


Implementation details: I currently propose to allow unknown
parseType values to be handled in three ways - 1) Return a string of
original content including <>s etc, 2) pass on XML SAX events, 3)
form as new XML content with any required namespaces defined locally.
For collections, there will be an API for the application to register
/ implement the collection methods when a collection resource type is
found and matches some [R]->rdf:subClassOf->[new-collection-uri]
statement.  The latter may not be necessary for most applications if
the collections interpretation in [3] is used.


Dave
Institute for Learning and Research Technology (ILRT), http://www.ilrt.org/


[1] Redland - http://www.redland.opensource.ac.uk/
[2] Rapier - http://www.redland.opensource.ac.uk/rapier/
[3] A Proposed Interpretation of RDF Containers - 
    http://www-uk.hpl.hp.com/people/bwm/rdf/issues/containersyntax/ 
Received on Tuesday, 30 January 2001 06:35:17 GMT

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