- From: Graham Klyne <GK@NineByNine.org>
- Date: Thu, 12 Jul 2001 18:37:40 +0100
- To: RDF core WG <w3c-rdfcore-wg@w3.org>
- Message-Id: <5.0.2.1.2.20010712174518.03011cd0@joy.songbird.com>
My proposal has gratifyingly generated some responses. (I would point out: this is isn't a clear-cut issue for me -- I am seeing some potent arguments for explicit support for some form of anonymous resources in the model/abstract syntax. But, I feel I must continue to play devil's advocate here to push down to the minimum requirements that must be supported/specified. Otherwise, I fear that we could end up with a whole load of baggage that really doesn't belong in the RDF core.) I include below a summary of the responses I have noted to date. In summary, the arguments _for_ anonymous resources in the model/abstract syntax are: (a) difficulty of creating globally unique genids (b) capturing semantics needed to express queries Are there more? ... To my mind, the most potent reason raised in response to my proposal for supporting anonymous resources (or similar) in the model is the difficulty and complexity of reliably generating a unique identifier, and the implications this has when combining RDF graphs. This represents a difficulty in dealing with M&S as currently defined and used. The other case that has been strongly argued is the requirement for variables in a query. While I can see the utility of what is being proposed, I have two problems with this: (a) I don't see anything in M&S that sanctions the idea of query variables: as such, this proposal seems to be a significant extension rather than clarification of the current M&S that we are chartered to do. (I'm not claiming this means that the query issue should not be addressed, but that we must be clear why and how far we might pursue it.) (b) I have a concern that anonymous resources are not exactly the right hook for attaching the query variable problem. A query requires that one can distinguish between known and unknown values in the query expression, and anonymous resources can provide that distinction. But when we take it to a different context, it seems that a very different interpretation of the anonymity may be desired. I find myself wondering if support for some kind of scoped identifier wouldn't address both of the goals raised. This would be in contrast to URIs which are, by design, globally scoped and bound to specific resources. I don't know if the semantics could play out simply yet sufficiently flexible to handle these goals. I think this, too, would be a clear extension to M&S. #g -- Summary of responses to anonymous resource proposal at http://lists.w3.org/Archives/Public/w3c-rdfcore-wg/2001Jul/0082.html. Aaron: [11-Jul-2001 12:47:33-0500] (a) Is OK that triples can contain anonymous entries, but not with a new anonymous resource type. (b) thinks genID algorithm should be specified. Sergey: [11-Jul-2001 14:26:07-0800] Agrees with Aaron about genID algorithm. Jos: [12-Jul-2001 12:17:24+0100] Thinks that anaonymous resources have NO name; cites empty circles. Ron: [11-Jul-2001 20:33:47-0700] Agrees with Aaron about (a), but "predefined" genIDs would be nice, not essential: [[[ I'd be happy with a non-normative convention suggesting how the IDs should be generated. I don't want it to be a MUST in the clarified spec. ]]] DanC: [12-Jul-2001 02:02:51-0500] Strongly feels anonymous resources must be represented in the model. Jan: [12-Jul-2001 10:36:54+0100] Anon resources are needed in the model. Jos: [12-Jul-2001 12:28:51+0100] Agrees with DanC. DanBri: [12-Jul-2001 07:29:33-0400] Warning about possible problems of generating same URI for same text in different context. Gives an example with a relative URI. StefanK [non-WG comment, posted to RDF-IG, 12-Jul-2001 09:38:28+0200] Thinks that forcing a system to invent names will cause problems. [[[ 1. An important application of RDF is the join of RDF graphs: By now named resources (with identical URI) are glued together, but anonymous are not. Please don't change this. ]]] and [[[ 2.1 I don't think there exists an algorithm that fulfills the requirement of your 'essential property of a unique URI' you mentioned above. ]]] Jan: [12 Jul 2001 14:19:28 +0100] Cites an earlier analysis, claiming it shows why anonymous resources are needed in the model. http://ioctl.org/rdf/discuss/anonymous#Complications ------------ Graham Klyne (GK@ACM.ORG)
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- text/plain attachment: Notes-anon-resource-20010712.txt
Received on Thursday, 12 July 2001 13:39:21 UTC