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As of this point the attendees have been TallTed, niklasl, olaf, ora, tl, gkellogg, fsasaki, gtw, AndyS, Tpt, pchampin, enrico, Souri, eBremer 13:55:48 Zakim has left #rdf-star 13:55:50 RRSAgent, bye 13:55:50 I see no action items 13:56:04 RRSAgent has joined #rdf-star 13:56:04 logging to https://www.w3.org/2024/08/23-rdf-star-irc 13:56:06 Zakim has joined #rdf-star 13:56:08 meeting: RDF-star Semantics TF 13:56:10 agenda: https://www.w3.org/events/meetings/6d0cd306-0be8-4267-865a-6272cc8d9da4/20240823T100000/ 13:56:11 clear agenda 13:56:11 agenda+ Which grammars for simple, RDF, and RDFS entailments? 13:56:26 meeting: RDF-star Semantics TF 13:57:00 niklasl has joined #rdf-star 13:58:07 AndyS has joined #rdf-star 13:58:21 agenda+ simple: fully unrestricted grammar? 13:58:21 agenda+ RDF: mandatory well-formed fragment? 13:58:21 agenda+ RDF: which metamodelling features? 13:58:21 agenda+ RDFS: introducing rdfs: asserts? 13:58:52 present+ 13:59:18 present+ 13:59:22 RRSAgent, draft minutes 13:59:23 I have made the request to generate https://www.w3.org/2024/08/23-rdf-star-minutes.html TallTed 13:59:28 RRSAgent, make logs public 14:00:08 present: AndyS, TallTed, niklasl, pchampin 14:00:16 RRSAgent, draft minutes 14:00:17 I have made the request to generate https://www.w3.org/2024/08/23-rdf-star-minutes.html TallTed 14:00:52 previous meeting: https://www.w3.org/2024/08/22-rdf-star-minutes.html 14:00:52 next meeting: https://www.w3.org/2024/08/29-rdf-star-minutes.html 14:01:01 gkellogg has joined #rdf-star 14:01:12 gkellogg has joined #rdf-star 14:01:43 RRSAgent, draft minutes 14:01:44 I have made the request to generate https://www.w3.org/2024/08/23-rdf-star-minutes.html TallTed 14:01:50 enrico has joined #rdf-star 14:01:50 tl has joined #rdf-star 14:01:52 present+ 14:02:03 present+ 14:02:03 present+ 14:02:43 I am in a train, so it would be better if somebody else chairs today 14:03:08 ora has joined #rdf-star 14:03:39 agenda? 14:04:15 scribe- 14:04:21 chair: ora 14:04:22 scribe+ 14:04:23 chair+ 14:04:26 present+ 14:04:27 gkellogg_ has joined #rdf-star 14:04:33 RRSAgent, draft minutes 14:04:35 I have made the request to generate https://www.w3.org/2024/08/23-rdf-star-minutes.html TallTed 14:04:51 Zakim, open item 1 14:04:51 agendum 1 -- Which grammars for simple, RDF, and RDFS entailments? -- taken up [from agendabot] 14:05:37 enrico: the current baseline says that you have RDF Simple (completely unrestricted), 14:05:44 https://github.com/w3c/rdf-star-wg/wiki/RDF-star-%22minimal-baseline%22 14:05:49 s/RDF Simple/simple semantics 14:06:01 ... then RDF semantics is restricted to the well-formed syntax 14:06:03 Souri has joined #rdf-star 14:06:09 ... then there would be RDF-S semantics. 14:06:34 ... Whether Simple RDF should be completely unrestricted is an open question. 14:06:59 ... Another open question is whether the well-formed fragment is strongly constrained. 14:07:32 ora: when you say "completely unrestricted", you don't mean things like "literals in the subject position" right? 14:07:58 enrico: no, I mean unrestricted when it comes to triple terms. 14:09:00 doerthe has joined #rdf-star 14:09:12 ... One option: capturing the semantics of rdf:reifies into the meta-model without any syntactic restriction. 14:09:12 present+ 14:09:28 q? 14:09:29 present+ 14:09:29 q+ 14:09:32 present+ 14:09:35 ack tl 14:09:36 ... Another option is to constrain syntactically the position of rdf:reify. 14:10:02 Zakim, who's here? 14:10:02 Present: AndyS, TallTed, niklasl, pchampin, enrico, tl, gkellogg, ora, doerthe, Souri 14:10:04 On IRC I see doerthe, Souri, gkellogg_, ora, tl, enrico, gkellogg, AndyS, niklasl, Zakim, RRSAgent, TallTed, driib5, csarven, gtw, gb, pchampin, ktk, rhiaro, Tpt, agendabot 14:10:32 RRSAgent, draft minutes 14:10:34 I have made the request to generate https://www.w3.org/2024/08/23-rdf-star-minutes.html TallTed 14:11:11 tl: I sympathize with the idea to allow any term in any position, but in the case of triple terms, we decided to be very restrictive (only with the rdf:reifies predicate...). 14:11:19 q? 14:11:32 ... So I don't see any value in allowing them in the subject position. 14:11:49 q+ 14:12:10 ... The reifier can be used in any position we like, so nobody is hurt by restricting triple-terms themselves in the object position. 14:12:13 ack enrico 14:12:21 pfps has joined #rdf-star 14:12:57 q+ 14:12:58 enrico: RDF simple already allows you to do whatever you want. 14:13:09 ... You simply do pattern matching over a meaningless graph. 14:13:15 q+ 14:13:59 ... RDF semantics add more semantics, RDFS adds more (inc. the notion of types). 14:14:15 ack ora 14:15:23 q+ 14:15:23 ... Only in RDFS do some IRIs have a specific semantics. 14:15:43 ... I suggest we do something similar for the semantics of rdf:reifies. 14:16:19 ora: RDF simple seems to justify some uses of RDF that I have seen, 14:16:32 ... which I don't like, but you can't prevent people from doing what they want. 14:17:07 ... To what extent do we want to *enfore* things. 14:17:37 enrico: in RDF semantics, there is no enforcement. Just new triple corresponding to the meta-model. 14:18:10 ... + entailment based on blank node abstraction. 14:18:16 ack pchampin 14:18:33 scribe+ 14:18:36 ... Only in RDFS do IRIs have a special meaning, provisioning for more entailment. 14:18:49 pchampin: reacting to Enrico 14:19:12 q+ 14:19:19 ...saying "pattern matching over a meaningless graph" worries me 14:19:45 we agree p-a 14:19:59 ... every IRI denotes something in the domain of discourse, predicates are binary relationships. 14:19:59 ack niklasl 14:20:33 pchampin: just to comment on Enrico's calling Simple semantics "meaningless". There is a semantics, so there is a meaning, even if very weak. 14:20:46 ... Happy to see on IRC that enrico agrees :) 14:20:53 scribe- 14:21:53 niklasl: in Simple RDF, literals are not allowed in the subject position, not just because they are not allowed in RDF 1.1, but because they do not belong there. 14:22:03 ... I don't think the same holds for triple terms. 14:23:16 q+ 14:23:37 ... I'm not sure where we should draw the line here. Entailment could lead anything to end up in the subject position (with inverse properties). 14:24:21 ... We should focus on the ergonomics of concrete syntaxes. We could *discourage* triple terms in the subject position, without strictly forbidding them. 14:25:22 ... We could have a concrete syntax for the generalized abstract model -- e.g. N3. 14:25:42 ... This would not be the general user interface, but some form of expert interface. 14:25:47 ack enrico 14:26:25 enrico: when I say that Simple RDF is meaningless, I mean that IRIs are not bound to any pre-defined entity. 14:26:59 +1 to this notion of meaningless 14:27:15 ... Even if you use an otherwise well defined IRI, in simple entailment, its meaning is lost. 14:28:04 ... Now, about the position of tripe-terms: even when restricted to object position, we can make meaningless statements (e.g. "john buys this triple term"). 14:28:08 q+ 14:28:21 +1 to concrete, full-fledged well-formed notion. 14:28:32 ack gkellogg_ 14:28:40 ... The only meaningful use of a triple-term is as the object of rdf:reifies. 14:28:55 gkellogg_: I can understand the arguments for allowing triple terms in the subject position. 14:30:03 ... I'm concerned about the impact on vendors if people start to use it. 14:30:20 :liz :spouse <<(:richard :loves :liz)>>. ???????? 14:30:21 +1 to restrict triple-terms to he object position only, and only when the predicate is rdf:reifies (or rdf:asserts, if we include that) 14:30:22 +1 to gkellogg_ ; it's about "guiding the usage" for me too 14:30:28 We need a "generalized-except-predicates are IRIs" 14:30:34 s/to he/to the/ 14:30:41 ack pchampin 14:30:48 scribe+ 14:31:36 enrico, but is "not preventing all misuse" an argument for "not preventing misuse" ? Or am I missing your written remark here? 14:31:43 pchampin: I'm OK with restricting to object only like literals 14:32:13 ... someone may come up with a predicate where is makes sense in the subject position 14:32:33 s/someone/at the same time, someone/ 14:33:00 :liz :spouse rdf:type. ????? 14:33:02 +1 pchampin, another predicate can come along to making sense (e.g. imagining a possible future RDF 1.x for graph terms being composed of triple terms, akin to lists... But *not now*.) 14:33:07 q? 14:33:10 q+ 14:33:15 ack AndyS 14:33:24 AndyS: I am neutral on this. 14:33:41 ... We have to align the concrete syntaxes with the RDF data model. 14:33:52 ... If we put anything in N-Triples, in must be in Turtle as well. 14:34:37 ... The simple should work, that what makes c14n, SHACL, SPARQL work. 14:34:59 ... Forcing the complex on everyone will cause problems. 14:35:21 q+ 14:35:23 ... Again, I'm neutral, we should have a strawpoll and see where everyone's opinion's are. 14:35:42 ora: are you advocating for less restrictive? 14:36:04 AndyS: SPARQL has literals in the subject position, as a natural consequence of variables. 14:36:13 I have no issues with SPARQL allowing that. 14:36:13 ... but if your data is correct, SPARQL will work correctly. 14:36:25 ora: implementations can rely on the assumption that the data is correct. 14:36:51 It already allows "Alice" ^foaf:name ?alice . 14:37:02 AndyS: if we talk about enforcing, then we are considering that data can be wrong, and should be checked. 14:37:55 ack doerthe 14:38:07 I'm not for "enforcing only sensible", I'm for "minimizing user error". 14:38:15 doerthe: I also agree with pchampin and enrico, I think. 14:38:29 ... I would prefer triple terms in the subject position, but I can live without that. 14:38:59 ... I would be opposed to restricting triple terms with specific predicates, such as rdf:reifies. 14:39:07 q? 14:39:08 q+ 14:39:09 q+ 14:39:15 ack niklasl 14:39:16 ... If we consider rdf:reifies to be a predicate, then other predicates should be allowed as well. 14:39:30 ... Otherwise weird things may happen with entailment. 14:39:42 ack enrico 14:39:48 niklasl: I agree. This kind of restriction should be a SHOULD at most. 14:39:58 gkellogg_: and that's what RDF concepts currently says. 14:40:26 enrico: ok for not restricting RDF Simple. 14:40:34 Souri8 has joined #rdf-star 14:40:38 present+ 14:40:54 ... In the meta-model, there should be a class of predicates that accept triple terms as objects. 14:40:58 RRSAgent, make minutes 14:41:00 I have made the request to generate https://www.w3.org/2024/08/23-rdf-star-minutes.html pchampin 14:41:44 [enrico breaking up, he writes what he wanted to say] 14:42:01 I'll write. I propose to have in RDF semantics the restriction that only predicates instance of a class rdf:reificationClass can have triple terms as objects 14:42:16 and that triple terms can be only in object position of such predicates 14:42:30 I can live with that 14:42:41 So to leave open the possibility that anybody could have her own interpretation of rdf:reifies 14:42:44 Pedantic: rdf:ReificationProperty ? 14:42:52 looks good to me 14:42:55 yest nikasl 14:43:13 ora: the question is then: if they are not, will there be crazy behaviour, or what? 14:43:19 Not crazy, but the meaning would be left to the user 14:43:25 +1 14:43:34 s/yest /yes / 14:43:52 what would be the advantage? Just to pint out 14:43:53 +1 maybe not spelled out "crazy" in the spec 14:44:00 q+ 14:44:00 point again ;) 14:44:08 ack AndyS 14:44:08 ANd we can have a RDF rule saying that A B tripleterm ==> B a rdf:reificationProperty 14:44:09 whishful thinking 14:44:10 If I say :r :myProp <<( :s :p :o )>> . Are we going to entail (using RDF entailment) that :myProp rdf:type rdf:ReificationClass . ? 14:44:35 Yes 14:44:58 s/whishful/wishful/ 14:45:08 Yes Andy 14:45:14 AndyS: to check my understanding, 14:45:37 yes to all 14:45:55 ... this mechanism (as described in the baseline document) would not go into a spec. 14:45:55 This means no well formed syntax anymore 14:46:07 but just the metamodelling rule above 14:46:10 yeah! :) 14:46:20 ah, ok, thank you enrico 14:46:28 Asking about this section - would it be removed -- https://github.com/w3c/rdf-star-wg/wiki/RDF-star-%22minimal-baseline%22#abstract-syntax-of-well-formed-rdf 14:46:44 q+ 14:46:44 yes andy 14:47:01 q+ 14:47:11 niklasl: being pendantic, a better name would be "ReificationProperty" 14:47:15 ora: yes 14:47:21 Are we going to state in RDF1.2 spec that "to start with, rdf:reifies by definition is an instance of the rdf:ReificationProperty class" 14:47:26 +1 niklasl 14:47:45 STRAWPOLL: Do you support the idea that in RDF semantics only predicates that are instances of rdf:ReificationProperty can have triple terms as objects? 14:47:57 +1 14:47:59 +1 14:48:00 +1 14:48:00 +1 14:48:02 +1 14:48:04 +1 14:48:09 -1, what is an instance? 14:48:13 +1 14:48:26 a instanceof b iff a a b. 14:48:28 0 (not sure yet, need to think) 14:48:44 rdf:reifies rdf:type rdf:ReificationProperty . 14:48:49 q+ 14:48:56 ack pfps 14:48:59 no pfps 14:49:11 ack gkellogg_ 14:49:14 pfps: what does "instance" mean in this strawpoll? 14:49:17 does the strawpoll mean that triple terms can appear in subject position? 14:49:25 it is just a metamodelling triple from rdf, just like may others 14:49:34 q+ 14:49:35 "instance" => an individual in the rdf:ReificationProperty class 14:49:48 :a :p :b ==> :p a rdf:predicate 14:50:30 no no gregg 14:50:31 ack enrico 14:50:40 gkellogg_: it adds some complexity 14:50:49 q+ 14:51:03 Pedantic: :p a rdf:Property . 14:51:18 True, but then there is no restriction. 14:51:41 enrico: whenever an IRI is used in the predicate position, it has rdf:type rdf:Property. Similarly, whenever a predicate has a triple term as object, it has rdf:type rdf:ReificationProperyt. 14:51:48 ... No check to be done. 14:51:48 ack pchampin 14:51:59 ack tl 14:52:08 Is it okay to assume OWA? Which means due to typo, rdf:deifies, could be come one such property. 14:52:16 q+ 14:52:18 s/be come/become/ 14:52:20 ack enrico 14:52:24 tl: does it implies that triple terms can not appear in the subject position? or is it still an open question? 14:52:32 gkellogg_: it is an orthogonal question. 14:52:43 +1 14:53:16 +1 14:53:17 q+ 14:53:25 q+ 14:53:32 ack niklasl 14:53:34 ora: I will have to drop for another meeting in 2 minutes. Are we happy with the discussion so far? Can we move forward in the agenda? 14:53:47 agenda? 14:54:16 niklasl: if a property is used with a triple term, it is automatically inferred to be a reification property. Is that the case? 14:54:17 What will happen to Turtle shortcuts? Would that apply only to pre-designated reification properties (like rdf:reifies, for example)? 14:55:05 ack tl 14:55:10 ... if I have ":alice :knows <<( s p o )>>", does that make :knows a ReificationProperty? 14:55:14 enrico: yes 14:55:22 q+ 14:55:24 Turtle shortcuts only generate RDF TripleTerm <<(...)>> in the object position. 14:55:26 ack enrico 14:55:47 tl: I'd like a strawpoll on triple terms in the subject position. 14:56:25 and also only :r rdf:reifies <<(:s :p :o)>> 14:57:05 q+ 14:57:06 I need to drop, someone else maybe take over chairing 14:57:25 enrico: with this meta-model, if a triple term occurs in the subject position, then the property will be entailed to be the inverse of a ReificationProperty. 14:57:54 -1 on triple-terms in the subject position 14:58:01 source - We could add a way to have a property but need to consider whether it is a "short" cut anymore. 14:58:26 q+ 14:58:33 s/source/Souri8/ 14:58:44 ack niklasl 14:59:17 niklasl: enrico, would you be against N-Triples no allowing triple terms in the subject position? 14:59:25 enrico: strongly against it. 14:59:28 q+ 14:59:37 s/no allow/not allow/ 14:59:46 ack tl 15:00:12 ack gkellogg_ 15:00:17 tl: we can have constraints in RDF in the abstract syntax, and I think we should. 15:00:58 gkellogg_: if we allow triple terms in the subject position in Turtle, we need to update N-Triples, and then the abstract syntax. 15:01:11 I dislike triple terms as subjects in N-Triples. I am *for* them in that position in SPARQL. Just as the case is with literals today. 15:01:32 ... I would be more inclied to allow them in the subject position if there was no way to express that in concrete syntaxes. 15:01:36 q? 15:01:36 q? 15:01:42 q+ 15:01:43 It is easier to allow it later on than to prevent it later on. 15:01:47 -1 to have abstract syntax construct not expressible in concrete syntaxes 15:01:49 ack enrico 15:01:53 +1 to niklasl 15:01:58 q? 15:02:10 q+ 15:02:15 q+ 15:02:37 ack enrico 15:03:06 enrico: the only reason that could convince me of disallowing triple terms in the subject position would be implementation concerns. 15:03:41 Should we say that a ReificationProperty cannot have an inverse property (similar to datatype properties)? 15:03:41 ... We should not assume that everyone implements things in a certain way, but if 99% of them do, them it would be a good reason. 15:03:50 ack pchampin 15:04:22 q+ 15:04:33 ack pfps 15:04:59 q+ 15:05:07 I agree with enrico, but if the fact that a property is an instance of ReificationProperty because it happens to have a triple term, it is not a restriction at all. So why are we having it? 15:05:23 enrico: this is a restriction for the user. 15:05:26 It can be enforced in OWL? (disjointWith) 15:05:34 ... It can not have any other meaning. 15:05:51 ... Just like using p in the predicate position forces it to be a property. 15:06:03 ... This is just meta-modelling, but it is useful to tell the user what they are actually doing. 15:06:04 ack enrico 15:06:41 ... People may not care about it, but it's there. 15:06:46 But then this "STRAWPOLL: Do you support the idea that in RDF semantics only predicates 15:06:46 that are instances of rdf:ReificationProperty can have triple terms as 15:06:46 objects?" doesn't mean what most people think it means. 15:07:19 pfps: but then most people will misinterpret the word "can" in the strawpoll. 15:08:38 STRAWPOLL: Any IRI used as the predicate of a triple whose object is a triple term denotes an instances of the denotation of rdf:ReificationProperty. 15:08:54 s/instances/instance/\ 15:08:56 +1 15:09:00 +1 15:09:00 +1 15:09:08 +1 15:09:10 +1 15:09:26 +1 15:09:35 +1, but this doesn't say very much at all 15:09:42 +0+0.5 15:10:01 s/+0+0.5/+0.5/ 15:10:19 +0.5 15:10:19 +1 15:10:27 It allows to have arbitrary predicates as reification predicates 15:11:00 opening the door to the different use cases, without problems about how to call such proeprties 15:11:22 q+ 15:12:25 q- 15:13:07 STRAWPOLL: Do you support allowing triple terms in the subject position? 15:13:11 +0 15:13:19 s/+0/ +0 15:13:25 -1 15:13:27 -1 15:13:28 +1 15:13:29 0 15:13:30 +1 15:13:33 -0.5 15:13:36 -0.9 (-1 for support in N-triples (and Turtle and TriG)) 15:13:40 +0.5 15:13:41 0 15:14:06 STRAWPOLL: do you support disallowing triple terms in the subject position 15:14:13 +0 15:14:13 +1 15:14:18 -1 15:14:20 +1 15:14:25 -1 15:14:31 +1 15:14:32 0 15:14:34 +0.9 (+1 to disallow in N-triples (and Turtle and TriG)) 15:14:41