- From: Graham Klyne <GK@NineByNine.org>
- Date: Tue, 03 Apr 2001 10:40:05 +0100
- To: www-rdf-logic@w3.org
It is with great interest that I have followed the thread about the adequacy of RDF. I think Peter F. Patel-Schneider captured a theme with these comments: >1/ There are many places in the RDF and RDFS documents where vitally >important statements about the semantics of RDF or RDFS are presented with >no formal backup, and in a totally inadequate fashion. [...] >2/ The triple model does not provide sufficient representational power to >transfer interesting semantic content. While fully accepting both of these statements, I'd like to try and make a case for not giving up on RDF: Regarding point (2): I shall assume that by "interesting semantic content", a level of understanding about some domain of discourse adequate for the purposes of a range of reasoning activities is meant. I guess this would be roughly what is required for software agents to negotiate autonomously and flexibly on behalf of their human "masters". I think there is a range of applications for which the expressive power of basic RDF is adequate. (e.g. RSS, calendaring, directory metadata, message metadata, web page metadata, etc., etc.) I think these will typically be applications in which human participants are still directly involved. For these applications, the expected value of using RDF is (a) to leverage common tools, and (b) to ease the movement of (RDF-coded) data between different applications, or to be able to combine data from multiple applications. Prosaic stuff, but still valuable. I also happen to think there are some simple rule-based systems (e.g. simple access control, directed searching, system component matching) that can be built using a kind of limited inference framework similar to that of RDF(S), which falls considerably short of FOL. Where I think things get interesting is if we can use this dull old common metadata format as a foundation on which to build the more interesting semantic content and reasoning elements. Because, if we can do this, the "semantically aware" components potentially have access to a wealth of raw data for their cogitations. Then the question I ask is: Is RDF adequate as a basis for building definitions of richer semantic capabilities? (I don't ask if it's the best base to build from, or complete, just if it's an adequate foundation. Someone reminded me recently that in the Internet standards area "the Best is the enemy of the Good".) I think the answer to this question, from what the logicians among us have been saying, is "Yes". I think there is value in the simplistic framework of RDG precisely because it is simple. For an Internet standard I think it would be a mistake to build up the base RDF so that the simple functions are no longer simple. Something I have learned is that Internet standards are often most successful when built in relatively small incremental stages. I think that, roughly speaking, RDF is the right size of step and would resist trying to put full semantic expression (whatever that may be) into the RDF core. The fact that we might build different semantic frameworks on that core is a real strength at this time. I don't think this is anything not already said, but it seems to have been lost in the recent debate about the semantic adequacy of RDF. Turning to point (1): I think that, in some respects, the RDF specification is its own worst enemy, and that the lack of comprehensive formal underpinnings may be part of the reason. As one who intends to be an active participant in the RDF review WG, I hope to do my part in rectifying this. I believe other participants will do likewise. But I think we have a significant job of education ahead of us: (a) education of the specification writers in the subtleties of formal underpinnings (e.g. is it a "model"? I know I have much to learn), and (b) education of the specification users; this means being able to draft the specification in such a way that the expectations of system developers who don't have a background in formal systems are set appropriately. I believe that truly outstanding experts in the field of logic and semantics are engaged here, and I truly hope that you will help us to get the formalities right this time, and to effectively communicate the necessary elements to the target audience of Web systems developers. #g ------------ Graham Klyne (GK@ACM.ORG)
Received on Tuesday, 3 April 2001 06:41:50 UTC