- From: Guha <guha@epinions-inc.com>
- Date: Thu, 04 May 2000 11:00:26 -0700
- To: Dan Brickley <danbri@w3.org>
- CC: Sergey Melnik <melnik@db.stanford.edu>, Jan Wielemaker <jan@swi.psy.uva.nl>, Dave Reynolds <der@hplb.hpl.hp.com>, www-rdf-interest@w3.org
Yes, Anonymity is not a property of the object, but a property of the description of the object. The situation is similar to indexicals. I can use "he" to refer to Dan, but that does not mean Dan is of type "he" or "indexical". guha Dan Brickley wrote: > On Thu, 4 May 2000, Sergey Melnik wrote: > > > Instead of associating semantics with URIs one could state it > > explicitly: > > > > book1 --author--> var:.... > > > > would become > > > > book1 --author--> whatever_URI > > whatever_URI --rdf:type--> rdf:Anonymous > > > > Interesting approach, but I don't think that quite works. We really > shouldn't be calling these "anonymous resources" as that leads us to > think that the resource itself is intrinsically nameless. That habit leads > us to solutions such as yours, which suggest that the anonymity is a > property of the resource, rather than of some mention or description of > the resource. Since I don't think anonymity is a property of the resource, > your proposal expresses exactly what I'm disagreeing with! > > I argued a similar point last month: > http://lists.w3.org/Archives/Public/www-rdf-interest/2000Apr/0022.html > > excerpt: > > Sometimes we don't know the commonly agreed ID for some entity, but > > nevertheless write some RDF statements that mention it in passing. When > > we send someone an RDF model and lack such URIs (sometimes because of > > partial knowledge; sometimes because social process > > doesn't exist to give uncontroversial URIs to these entitites) we still > > need to represent those entities in some kind of data structure. > > > > So these are the so-called 'anonymous resources'. I really think this is a > > bad name; it suggests that the anonymity is in some way intrinsic to the > > resource. That's not the case: rather, some 'mention' of that resource is > > anonymous in that we happen not to name the resource on that occasion. > > I agree with you that associating semantics with special URI schemes for > use with RDF isn't a great solution, but feel the analogy with variables > makes this worthy of some investigation. > > RDF's world consists solely of Web-nameable resources (things for which > the notion of identity makes sense, and which may/might/can have URIs) and > un-nameable (intrinsically anonymous??) literal strings. RDF applications > that express queries, inference rules etc. typically add to this some > notion of a variable. eg. TimBL's DesignIssues work > (eg. http://www.w3.org/DesignIssues/Toolbox.html) makes a stab at doing > this. > > Anyone representing rules/queries over RDF content (and hence > using variables) needs to decide whether those data structures will > themselves have a representation in the RDF 1.0 Model, or whether they'll be > inexpressible in the core model and be represented in a superset of RDF > 1.0 that has an explicit notion of variables. As Tim says in the Toolbox > doc. (discussing NOT, rather than variables, but general point holds)... > > 'As RDF has little power at its basic level, anything new has to be > introduced by reification - by describing it in RDF. Hence, to say > "not(node, property, value)", you have to say, for example, "there is > something which is an RDF property and has a subject of A and whose B > property has vale C and is false". ' > > So if I want to represent variables within an RDF context, we either > find a hack that appeals (eg. "var:" IDs) or admit that certain things are > not elegantly represented in base RDF (although of course they can be > "tunnelled through" the RDF triples model, ie. quoted > but not understood by most 1.0 processors). > > I've seen quite a few systems tunnel rules (containing variables) over > RDF, eg. Jos De Roo's work (ftp://windsor.agfa.be/outgoing/RCEI/NET/euler/index.html) > which lead me to suggest that the anonymous node problem and the > tunnelling-data-containing-variables-through-RDF problem are two views of > the same issue. In both cases, we need to represent to machines the fact > that we don't know the Web names for various entities, but nevertheless > know some other things about them. Whether the definition of URI/Resource > is broad enough to be used for variables is an interesting > (religious?) question. Reading RFC2396 I'm inclined to suggest that this > is acceptable: > > Excerpted from related thread at > http://lists.w3.org/Archives/Public/www-rdf-interest/2000Mar/0028.html > the RFC tells us... > > i) A Uniform Resource Identifier (URI) is a compact string of characters > for identifying an abstract or physical resource. > > ii) A resource can be anything that has identity. > > and in particular this rather cryptic paragraph: > > iii) > > The resource is the conceptual mapping to an entity or set of > entities, not necessarily the entity which corresponds to that > mapping at any particular instance in time. Thus, a resource > can remain constant even when its content---the entities to > which it currently corresponds---changes over time, provided > that the conceptual mapping is not changed in the process. > > Now this in particular sounds to me a lot like our current problem... > > Dan > > -- > mailto:danbri@w3.org
Received on Thursday, 4 May 2000 13:53:57 UTC