Part of F2F1 Minutes.
OWL Working Group Meeting Minutes, 07 December 2007
DRAFT. Currently Under Review
See also: IRC log
- Evan Wallace
OWL DL and OWL Full
Slides for this session: Media:pfps-f2f1.pdf (pp. 1-3)
Here's a brief description of how model theoretic semantics works
Peter Patel-Schneider: OWL DL has a fairly straightforward take on this
Peter Patel-Schneider: OWL Full and RDF take a slightly weird take on this
Peter Patel-Schneider: wherein properties and classes live in the world with real objects
Peter Patel-Schneider: Here are the differences between OWL DL and Full semantics
See "Two Model Theories" slide
Peter Patel-Schneider: things like rdf:type and owl:Class are not in the world in DL but are in Full
Alan Ruttenberg: In OWL DL Universe what is the status of Ontologies?
Peter Patel-Schneider: There is a separate place for them because of annotations
Peter Patel-Schneider: This description is about the specification and not practice
Bijan Parsia: The things in the OWL Full universe are in there with a theory
Peter Patel-Schneider: None of this matters in some sense
Peter Patel-Schneider: What matters is the behavior which results
Peter Patel-Schneider: ...such as entailments
Peter Patel-Schneider: Differences: It's possible to make assertions about the OWL vocabulary that change their interpretation
Slides for the rest of this session: Media:carroll-f2f1.pdf
Jeremy to take over presenting
Alan Ruttenberg: question about the intention of compatibility to be entailments of DL and Full be identical
Jeremy Carroll: for me the whole point is to get compatibility with RDF
Jeremy Carroll: A goal is "least surprise" for users of RDF when using OWL
Jeremy Carroll: OWL annotations are intended to behave as RDF annotations
Alan Ruttenberg: There are implications for RDF annotations that users may not be aware of
Alan Ruttenberg: I want to make a distinction between usage and consequences of the semantics
Bijan Parsia: I don't understand what you mean by RDF triple-by-triple semantics
Jeremy Carroll: In the OWL 1.0 semantics there are correspondence theorems between OWL Full and DL Semantics
Jeremy listed Issues related to the FULL and DL differences
such as 63, 76, 81, 69, 72, 55, 73
Jeremy Carroll: Do we want to allow semantic subsetting for fragments
Bijan Parsia: If we are going to support OWL Full do we need to support the full RDF umbrella
Bijan Parsia: described in Jeremy presentation
Jeremy Carroll: The semantic of RDF reification are essentially none
Bijan Parsia: There exists somewhere in the known universe a Statement that includes: S, P, O
Jeremy Carroll: There is no clear statement in the specs for how reification can work interoperably from system to system
Bijan Parsia: In the OWL full situation you have to interpret the reification syntax somehow
More discussion about how this can be done
Jeremy Carroll: Punning
In some peoples mind the web arch specifies that a URI corresponds to a single meaning
Punning is weaker than OWL Full because it violates this principle
Jeremy Carroll: this seems to cause user confusion
In my view, the mapping rules were the hardest part of the OWL Rec
Jeremy Carroll: The drivers behind the mapping rules in OWL 1.1 are different
Jeremy Carroll: ...and this will lead to considerable change and probably
Boris Motik is speaking
Jeremy Carroll: ...issues later on.
Boris Motik: In my opinion many of these problems are the result of
Boris Motik: ...shoe-horning everything in the same universe.
Point for discussion later:
Boris Motik: if we came up with an OWL Full that has a clean model theoritic framework
...then we could fix this.
Alan Ruttenberg: This would be a smaller OWL Full?
Bijan Parsia: Punning was intended to meet the goals of Full at least quarter way
Peter Patel-Schneider: The dogma in this case is the same syntax extension of RDF
Bernardo Cuenca Grau: The people who like OWL Full should really come up
...with features for OWL Full that they like and use
...Then we could do some research.
Ian Horrocks: The point I wanted to make was how much of this proposed
...work will be part of the work of this WG?
Boris Motik: Cleaning this up would be a huge accomplishment for this group.
Alan Ruttenberg: To my mind, it's not clear that cleaning up OWL Full is desirable to
... the Full/RDF community.
Jeremy Carroll: Dropping the comprehension principles seems like the
... smallest change that would be of value.
Alan Ruttenberg: Is this in scope for our group? Strictly speaking I don't think so.
Ian Horrocks: This kind of work just isn't in scope.
Bijan Parsia: Form an OWLED task force to look at this.
Alan Ruttenberg: We need to have a discussion about what compatibility means.
Alan Ruttenberg: If we allow OWL Full semantics changing that will affect backwards compatibility
Discussion of semantic fragments
Alan Ruttenberg: we have a delta now in the sublanguage entailments
Bijan Parsia: finding some delta that makes sense that makes the languages
...as close as possible would be a good thing.
Ian Horrocks: If we are comfortable with this semantic subsetting then
... we should be happy with the Full - DL differences
Ian Horrocks: One slight difference in Jeremy's proposal would be allowing
... more syntactic freedom but actually reducing the entailments
... by removing the comprehension principles for e.g.
Jeremy Carroll: HP might be happy with such a result if it is consistent
... with some broader framework.
Jeremy Carroll: There are easy bits in the OWL 1.1 language.
... getting those bits working are a bounded and achievable task.
Bijan Parsia: My experience is that users are concerned about not
... being able to process large numbers of RDF graphs
...with DL reasoners.
... Features like punning improves this situation.
Ian Horrocks: I wonder how hard it would really be to extend the status quo
... with some acceptable differences.
Ian Horrocks: This is a strawman for something that we could do.
Jeremy Carroll: I'd need to take this proposal back to HP before commenting on it.
Bijan Parsia: I would like us to keep the political and the user requirements seperate
ACTION: jeremy describe how punning and cardinality play poorly with each other
Ian Horrocks: I'd like to see suggestions for concrete ways of moving forward to address these problems
Jeremy Carroll: Why don't we start with Qualified Cardinality Description?
Peter Patel-Schneider: Someone made comment that Qualified Cardinality Descriptions leads to non-monitonicity
... and I remember finding it believable
ACTION: pfps inform the WG on absurdity of QCR / OWL Full
ACTION: jeremy attempt Wiki sketch of QCR semantics OWL Full
Alan Ruttenberg: on concrete actions...
... we have a set of options
Jeremy Carroll: a suggestion that Jeremy concentrate on OWL Full
... Semantics and drop out of User Facing Documents
Alan Ruttenberg: Any other specific proposals?
Ian Horrocks: Let's try and extend where are now and see where we end up.
Alan Ruttenberg: When do we evaluate when this approach is failing
... so that we can try another approach?
... I want to have some ideas about where we would go if this
... doesn't work.
Jeremy Carroll: We have had two variants proposed today.
... Sacrifice backwards compatibility and work towards 1.1
Bijan Parsia: We are spending a lot of time on this.
... I would like to know how much interest in this WG
... with Full compatibility.
How many people want to use OWL Full for 1.1?
Jeremy rephrase: When using 1.1 do you want to use Full semantics?
5 yes in room 15 no
q2 Are you a potential customer for Bijan's description of patch-up rules?
many in favor