- From: Dan Brickley <danbri@w3.org>
- Date: Thu, 2 Aug 2001 12:33:41 -0400 (EDT)
- To: <www-archive@w3.org>
(drafted notes)
F2F Day 2: RDF Schema 1.0 Discussion
Progressing RDF Schema:
- dan b (rdfs editor)
- brian m (chairing)
What are we trying to achieve?
-----------------------------
- agree a closure of our 2 active open issues
- seeking working hypotheses on other RDFS issues for next WD
(see how many we can crank through in ?n minutes)
- understand the context and status of RDFS
Context:
-------
* RDF Schema is a W3C Candidate Recommendation. This means W3C
community consider it "as good as done; need implementor feedback"
* RDF Issue List, DAML+OIL feedback provide this feedback
* We waited for XML Schema datatypes; DAML+OIL makes a proposal for
these in RDF
* How much flexibility:
- more flexible than M+S, in that we're not fiddling with a
"Recommendation";
- less flexible: RDFS isn't as contested/buggy, a CR means "almost done"
- time/resources: we have our work cut out with the model/syntax; if we
spend a lot of effort on RDFS polishing, we distract from the M+S work.
* RDF Schema is one major application of RDF Core's Model+Syntax work;
progressing RDFS is a an important sanity check for the M+S work.
* W3C context:
- Other WGs are using this spec (CC/PP, P3P, WAI EARL)
- A successor WG is planned
to do "RDF Schema 2.0" aka "Web Ontology" (DAML+OIL+???)
- we did the right thing and waited for XML Schema; now its time
to get this thing moving again.
- Simplicity Simplicity Simplicity: XML Schema took 3 years and a
huge WG to publish a rather complex spec;
W3C and RDFCore can't afford to do this. RDF Schema's value is
in its simplicity,
and (we hope) genuine extensibility: fancy stuff comes later.
(3 years ago we discussed class specific constraints,
intentionally defined classes etc for RDFS; the RDFS design
leaves these to future work; a WebOnt WG will probably do
that work).
How to make progress
--------------------
We note:
* Our next step is not our last step: we work to draft some answers to
implementor feedback
* for each of these issues, we need a working hypothesis for our Working Draft(s) *
* Consensus:
- we do not need 100% consensus to publish Working Drafts
- we have a duty to document and acknowledge dissent (within WG,
W3C and wider community)
* Strawpoll answers to (some) open issues, edit these into an RDF
Schema WD, and see how it looks _as a spec_ (for us, and wider
community; users of rdfs 1.0)
* There will be opportunities to refine the spec (and decisions) in
light of further testing
* If we get strawpoll answers to all issues, Eric will eat a spoonful
of vegemite.
Opened Issues
-------------
rdfs-domain-and-range: Should a property be allowed more than one
rdfs:range property? What should the semantics of
multiple domain and range properties be? (Dan Brickley)
PROCESS: We can spend 5, 10, 20 or 45 minutes on this. Or 2 days. But we
*must* come out of the discussion with an ACTION for the editor. Or
we don't go home. (for brian: time mgmnt 10 mins?)
PROPOSAL: * conjunctive semantics for domain and for range
* multiple ranges are not forbidden
[discussion point...]
rdfs-domain-unconstrained: The rdfs:domain and rdfs:range constraints for
rdfs:domain are missing from the RDF
Schema for RDF Schema (Dan Brickley)
PROPOSAL: * editorial oversight
Other RDF Schema Issues
-----------------------
rdfs-constraining-containers: Should it be possible to constrain the
members of a container to be of a given type?
PROPOSAL: * No compelling case has been made for additional features in 1.0
* We already allow subclasses of the containers
* Other languages (DAML+OIL; WebOnt; Prose...) can express those constraints
rdfs-xml-schema-datatypes: A suggestion that the RDF Schema Spec
might usefully use XML Schema datatypes in
examples and/or in some formal specification of the mapping of these
datatypes into the RDF model.
PROPOSAL: * Adopt the DAML+OIL implementation as an intial foray
into this issue
* Seek implementor feedback on this explicitly in our next WD
rdfs-primitive-properties: A suggestion that properties such as
rdfs:subClassOf, rdf:type and others should not be
instances of rdf:Property, but should be primitive
PROPOSAL:
* Not critical path for next working draft
* The model theory (and associated documentation) tells us
what rdfs:Class is an rdfs:Class means.
Defer to model theory.
rdfs-no-cycles-in-subClassOf: Cycles of subClassOf properties are
prohibited
PROPOSAL: * Not critical for next WD
* No change in this draft, but note we're not married to
current design
rdfs-subPropertyOf-semantics: The inheritance semantics of the
subPropertyOf relationship needs to be clarified.
PROPOSAL: * Not critical path for next WD; do after Model theory
rdfs-subClassOf-a-Property: Clarify whether a Property can have a
subClassOf property, and if so, what that would
mean?
PROPOSAL: * with the range/domain fix, this becomes: are Property
and Class disjoint
* strawman: yes they are, so it can't.
rdfs-online-char-encoding: There is problem with the character
encoding of the online RDF Schema.
PROPOSAL: * editorial oversight
* spend no time here talking about whether to change ns uri
rdfs-versioning: RDF Schema does not deal adequately with versioning.
PROPOSAL: * known hard problem; defer.
rdfs-transitive-subSubProperty: Is a sub-property of
rdfs:subPropertyOf necessarily transitive?
PROPOSAL: * take this to the mailing list / telecon. not good f2f issue.
rdfs-clarify-subClass-and-instance: Suggestion of clearer discussion
of use of subClass and instance relationships
simultaneously.
PROPOSAL: editorial wordsmithing needed,
rdfs-isDefinedBy-semantics: Must the value of an rdfs:isDefinedBy
property be a schema?
PROPOSAL: not critical path
rdfs-editorial: General editorial comments.
PROPOSAL: so noted.
Received on Thursday, 2 August 2001 12:33:41 UTC