- From: Patrick Stickler <patrick.stickler@nokia.com>
- Date: Tue, 16 Apr 2002 21:34:45 +0300
- To: RDF Core <w3c-rdfcore-wg@w3.org>
It seems that the fundamental, practical "get the job done" point of RDF Datatyping is not a point of concensus of the WG, much to my disappointment, so I thought I'd briefly summarize what I consider it to be. Who knows, maybe we really do all agree about the following... ;-) RDF has no native representation for any datatyped values. It knows nothing about integers, dates, strings, etc. And this is a good thing, because it keeps RDF platform and system independent, which one would expect from a standard intended for the global interchange knowledge. Literals belong to a pseudo catch-all datatype that is not much use insofar as "real" datatyping is concerned. But it has a simple job to do and it does it well. It represents strings. Plain and simple. Fair enough. What is needed is a way for system A to exchange datatyped knowledge with system B in a manner that is independent of either systems native representations yet which will preserve meaning across that exchange. Take the following example: System A 8506131627 | V <date,"1985-06-13T16:27:00"> | V [RDF Graph] | V <date,"1985-06-13T16:27:00"> | V "00198506131627000000" System B The underlying, native representation for dates is different for each system, but the representation of interchange is standardized. And what counts most is not the particular idiom used in the RDF graph, but that it is unambiguous and consistent in which datatype context the lexical form is to be interpreted by System B in order to obtain the value originally expressed by System A. Now, it may be that system B doesn't know what 'date' means, in which case, it's stuck. But if it does know what 'date' means, then it knows which value is identified by the pairing <date,"1985-06-13T16:27:00"> which is unambiguously expressed in the RDF graph by a particular idiom, and can map that pairing to the actual value, as it is represented within system B. For various practical reasons, how those pairings are expressed in the RDF Graph varies, and each variation is called an idiom. And the sole purpose of an idiom is to capture a pairing of datatype and lexical form. Thus, the very heart of RDF Datatyping is the "literal-in-context", the pairing of the lexical form with a datatype, a datatyped literal, whatever you want to call it, it's all the same. An idiom is just a means to that end. Period. Yes, it's important for those idioms to be well defined, and for there to be as few standard idioms as possible (simply for practical reasons). But "all idioms are created equal" in that their common purpose is to associate a lexical form with a datatype context for consistent and unambiguous interpretation. Whether or not folks want/need the datatyping MT to provide a formal definition for such datatyped literal pairings seems an open question. It could be argued that failure to capture such a fundamental basis of datatyping is a shortcoming of the MT, or that the MT is to that extent incomplete. This is not to criticize Pat's excellent work, but simply to suggest that perhaps it is not finished. Personally, I don't need it in the MT. Sections 1-4 work just fine for me (and probably will for most RDF users). But if others will sleep better with a formal MT definition, that's also quite fine by me. I certainly appreciate such concerns and am happy to do what I can to help address them. I don't consider the present WD to shift the stake in the ground one bit. Now, perhaps extending the MT to provide a formal definition of datatyped literal pairings would require a little twisting or bending at the stake, but it also probably wouldn't pull it out. Anyway, just thought I'd get that off my chest before going to bed... Cheers, Patrick -- Patrick Stickler Phone: +358 50 483 9453 Senior Research Scientist Fax: +358 7180 35409 Nokia Research Center Email: patrick.stickler@nokia.com
Received on Tuesday, 16 April 2002 14:31:58 UTC