Meeting minutes
Approval of minutes from the last two meetings: 1 , 2
ora: Approval of minutes
<ora> PROPOSAL: Approve last two weeks' minutes
<enrico> +1
<ora> +1
<niklasl> +1
<eBremer> +1
<AndyS> +1
<tl> +1
<william_vw> +1
<gkellogg> +1
<Adrian> +1
<gtw> +1
<TallTed> +1
<rubenswo_> +1
<olaf> +1
<Dominik_T> +1
<pfps> +1
<fsasaki> +1
RESOLUTION: Approve last two weeks' minutes
Proposed resultion by Semantics TF 3
enrico: There was a proposal to simplify the well-formed fragment so that it is not needed.
… Whenever there is a triple who's object is a triple term the semantics say that the predicate is of type rdf:ReificationProperty.
… This makes the system flexible, as in Turtle there is a short-cut to introduce a reifier with a triple term without mentioning the predicate, so there will be an rdf:reifies predicate coming from that expansion.
<enrico> https://
enrico: I fixed the semantics baseline to deal with thils.
… The new version of the baseline gets rid of the well-formed semantics.
ora: What does this buy us. And, what are the downsides of this?
enrico: It means we don't need a well-formed syntax; you can write whatever you want.
… It also introduces the notion that triple terms only make sense in the object position.
… It maintains the "do whatever you want" philosophy of RDF, although it will have some meaning.
ora: If I use something which is not a property, I get nonsense.
enrico: You get a warning, as among the entailed triples you get something that does not sound correct.e
… This is typical with reasoning. You might derive something from your knowledge that is wrong, which means you need to go back and fix it.
… The entailment is interesting when you ask why something is an inferrence of rdf:ReificationProperty.
… The idea is that people will just use the short-cut, so it will always make sense.
ora: Should we add something saying that implementations are free to warn the user.
enrico: It's an entailment, so you assume that users mean what they say.
ora: This is in line with our earlier thinking; if you do something that's not okay you get something out which is not okay.
<enrico> Any IRI used as the predicate of a triple whose object is a triple term denotes an instance of the denotation of rdf:ReificationProperty.
enrico: This is what we voted on last Friday.
william_vw: Is rdf:ReificationProperty a sub-property of rdf:Property?
enrico: Yes. The modeling parts are discussed at the end.
<pfps> Remember that subclass and subproperty in RDF need to be stated - they never arise because of subset relationships
william_vw: I was talking with Doerte and she made the point that you can always infer that any object of rdf:ReificationProperty, as it is a sub-property of rdf:Property, you can infer that a property :x is used in a triple with a triple term.
enrico: We may have something to fix.
… In principle, this should not happen.
ora: Do you want to fix this before we vote on it?
enrico: I'll let you know.
pchampin: I may be misunderstanding, but I don't think there is an issue ...
… My understand that rdf:ReificationProperty is a sub-class of rdf:Property. Not a sub-property of anything.
… There may be a question if every reification property is a sub-property of rdf:refies, but not necessarily.
… That doesn't man that the presense of a property used with a triple term would entail some other property.
enrico: In RDF simple entailment, we use classes and instances of classes. This does not say anything about sub-properties.
<niklasl> +1 rdf:ReificationProperty rdfs:subClassOf rdf:Property .
william_vw: But, it's not the case that everything needs to be a sub-property of rdf:Property?
enrico: :s :p <<(...))>>> does not imply :p a sub-property of rdf:refies.
william_vw: I thought that everything in the property position can be inferred to be a sub-class of rdf:Property.
<pchampin> I think that William confuses rdf:Propety with owl:topObjectProperty / owl:DataProperty
niklasl: OWL has some other things, but RDF is simpler.
<Souri> Would this be allowed in a graph? ==> :x :firstName "John" . :y :firstName <<( :s :p :o )>> . (I hope not.)
gtw: What is the value of having this rdf:ReificationProperty?
… The sematantics seem to say it is entailed, but what do we get from that?
<tl> https://
enrico: You don't get anything, but it suggests that such a property is a rdf:ReificationProperty.
gtw: Why do it then?
… If it doesn't mean anything.
enrico: All of these entailments don't mean anything, but they help with understanding the model.
… It helps you to debug your graph.
<TallTed> Do we have an explicit draft proposal, of the thing that we might be voting on? That might help this discussion...
enrico: rdfs:Resource is also pointless.
gtw: We're not discussing changing those things, but I don't see the value of adding this if we think it's pointless.
<AndyS> rdf-semantics -- """rdfD2 xxx aaa yyy . aaa rdf:type rdf:Property ."""
enrico: It does not enrich your graph semantically, but allows you to see the entailments.
gtw: It's not saying that everything in the domain is a triple term.
enrico: It's like entailment, if you compute some entailments, that are also pointless, as they are of necessity already true.
… This allows you to increase your trust in the graph. If you see something clearly false, you have something to fix.
… Entailment is pointless, because it is already true. But, when you see it you learn something about your data.
ora: This matches my experience. It's helpful when building tooling.
tl: I understood this as a guide. You can define properties with more specific capabilities, but this is really just documentation
william_vw: I think Souri had some reservations that I asked to be clarified.
<Zakim> Souri, you wanted to ask Would this be allowed in a graph? ==> :x :firstName "John" . :y :firstName <<( :s :p :o )>> . (I hope not.)
william_vw: It would be more difficult to implement, and would lead to users messing up their data.
Souri: The original idea was to be minimal; we get a triple term who's only value is to define a reifier to talk about the triple term.
… When you see rdf:reifies, expect a triple term. That worked well from a minimalist point of view.
… when we introduce rdf:ReificationProperty, we shouldn't allow things that aren't aligned with the intention of ReificationProperty.
… Are we going to allow this, or not?
… I don't want to allow mixed use of Triple Terms.
… I see :firstName :John, and later <<(...)>>, it introduces a problem.
… If we allow any property to used, then by virtue of RDF Entailment, this causes a conflict.
… I'm not sure we need to bring in the rdf:ReificationProperty, we only need rdf:reifies.
… I'm not sure what we're getting out of it other than to find inconsistencies.
enrico: It would be more complex to impose such a restriction.
… Triple Terms can't appear elsewhere, so you need to defined a well-formed syntax.
… It's not obvious that having an enforced syntax is simpler than using the entailments to flag misuse.
tl: I think it's necessary to define an extension point for triple terms and rdf:reifies. If the group doesn't support asserts/states, then I would be in favor of the rdf:ReificationProperty.
… I am for prohibiting triple terms in the subject position, but not for other hard restrictions.
pchampin: Souri's concerns reminds me of another discrepancy: that with literals.
… Some implementations recognize xsd:integer and will reject literals that are invalid.
… But, the abstract data model allows them to be stated.
… The same can occur with rdf:ReificationProperty.
… We already use this type of flexibility unconsciously; the reasoning holds here too.
… By not insisting on well-formedness this allows some implementations to be more strict.
ora: Not quite ready to vote on now.
Souri: My phylosophy is that if you give people too much freedom, they will mess up.
… People will try to do things that don't make sense.
… Unless there is a substantial benefit, it may be better to not allow it to be stated.
… If we have rdf:reifies, we can do anything with the reifier, including to give it a type.
… The rdf:reifies hook gives us the ability ...
<Zakim> gtw, you wanted to mention that RDF 1.0-style reification will make any restriction on rdf:reificationProperty difficult due to rdf:object
fsasaki: I agree with Souri
gtw: In RDF 1.0 reification, it would be hard to do these sorts of restrictions.
… I don't see the value in rdf:ReificationProperty.
… It would be unfortunate if we got to the point where we said it was okay to violate such restrictions.
<TallTed> Please, please, can the agenda (and mailing list) include explicit text of proposal(s) on which we aim to vote? A link to a complete page of meeting minutes doesn't help advance prep much if at all.
ora: People should think about this.
Proposal for next week's discussion
ora: Anything else to discuss next week?
tl: I'd like to discuss rdf:states/rdf:asserts.
<AndyS> Is there anything we need to do for TPAC?
ora: Another good discussion for next week; what do we want to accomplish at TPAC?
enrico: Another thing related to rdf:ReificationProperty is the unrestricted nature of RDF, and if triple terms should be restricted from being used in the subject position.
<tl> s/rdf:asserted/rdf:asserts
ora: We can continue with today's discussion and get into some of these other issues.
… I don't think we need to vote on these, as they are clear discussion topics.
niklasl: I think the detail about naming the range of rdf:reifies is baked into the discussion.
Review of pull requests, available at 4
ora: There are several editorial things.
… It would be nice if we could see how long things have been open.
gkellogg: plan to merge w3c/rdf-turtle#62 after the meeting.
<gb> Pull Request 62 Add processor state, term constructor, and triple constructors. Change reifiedTriple to reifingTriple. (by gkellogg) [spec:editorial]
rubensworks: w3c/
… There are several about migrating from quoted triples to triple terms/reifiers which have good reviews.
… I think they can all be merged.
… Including Andy's update to the SPARQL grammar.
ora: No objections heard. General agreement that all open PRs can be merged.
AndyS: I think it's important to get the grammar in.
gkellogg: I think w3c/rdf-tests#135 needs to be merged.
<gb> Pull Request 135 Updates Turtle tests to use triple term syntax and reifications (by gkellogg) [enhancement] [Turtle]
AndyS: It's a bit more complex. It depends on what the expectations are.
gkellogg: I'd rather merge sooner rather than later.
AndyS: I wanted to point out that people may not have implementations ready to do good validation.
ora: I agree, lets merge.
Issue Triage, available at 5
ora: we're almost out of time, but I urge people to examine open issues to see what they may want to work on.
… We can pick up some of these items in due course, maybe at TPAC.
ktk: I think we want to spend some time together to go through the lists.
Any Other Business (AOB), time permitting
ktk: we have a couple of new members, although they're not on the call.
pchampin: University of Oxford joined with Ian Horrocks.
ora: Oxford Semantics was just acquired by Samsung.
Julian: I'm a PhD student at Universidad Politécnica de Madrid. I have already worked with RDF-star.
ora: Welcome!
<TallTed> yes, Samsung is W3C member -- https://
TallTed: It would be helpful if we could have explicit proposals for what we're voting on, not pointers to discussions.
<gkellogg_> s|<tl> s/rdf:asserted/rdf:asserts||