- From: pat hayes <phayes@ai.uwf.edu>
- Date: Wed, 5 Feb 2003 13:41:52 -0600
- To: "Peter F. Patel-Schneider" <pfps@research.bell-labs.com>
- Cc: www-rdf-comments@w3.org
>The RDF primer, in Section 2.2, states > > Using URIrefs as subjects, predicates, and objects in RDF > statements allows us to begin to develop and use a shared > vocabulary on the Web, reflecting (and creating) a shared > understanding of the concepts we talk about. For example, in > the triple > ex:index.html dc:creator exstaff:85740 . > the predicate dc:creator, when fully expanded as a URIref, is an > unambiguous reference to the "creator" attribute in the Dublin Core > metadata attribute set (discussed further in Section 6.1, a > widely-used set of attributes (properties) for describing > information of all kinds. The writer of this triple is effectively > saying that the relationship between the Web page (identified by > http://www.example.org/index.html) and the creator of the page (a > distinct person, identified by > http://www.example.org/staffid/85740) is exactly the concept > identified by http://purl.org/dc/elements/1.1/creator. Moreover, > anyone else, or any program, that understands > http://purl.org/dc/elements/1.1/creator will know exactly what is > meant by this relationship. > >This appears to me to state that the meaning of tokens in RDF *is* >their commonly agreed on meaning, regardless of how that meaning is >specified. Yes, in a sense, but... >If so, this means that RDF reasoners are responsible for >implementing this meaning. ....no, because that conclusion follows form a different sense of 'meaning'. See below. > >Is this actually the case? If so, how can RDF reasoners be implemented? >If not, please explain what the above quote means. (Speaking for myself here, not with the voice of any official WG, but what the hell...) My own reading of this issue agrees largely with yours, Peter, but I do not draw the apocalyptic conclusions that you do from it. I think you are reading more into it than is intended. The point is that there is not a single notion of 'meaning' being used in these debates. The above passage refers to a broader sense of 'meaning' than the one specified by the model theory. Let me take a very simple example to illustrate the point. Suppose some RDF is published by A with the following form: #antelope rdf:type rdfs:Class . #antelope rdf:comment "This is intended to be the class of all antelopes, considered as a species." and B uses this uriref in some other place as follows: #Arthur rdf:type A#antelope . Now, nothing much follows formally from these two taken together: but a person (not some RDF software) reading this, and knowing the formal meaning of things like rdf:type, might well conclude that B's intention was to assert that Arthur was an antelope. I hope you don't find this a ridiculous or philosophically risky observation. The point of all this 'social meaning' talk is only to say that 'meaning' in this very loose, broad, warm fuzzy human sense (which we do not need to make precise: choose your own sense, in fact) is not somehow cancelled or abrogated whenever one performs a formal inference using RDF. So for example, if B also asserts the RDF: #PetAntelope rdfs:subClassOf A#antelope . Joe rdf:type #PetAntelope . then the formal RDF semantic rules allow one (human or machine) to conclude that Joe rdf:type A#antelope . and - and this is the point - the fact that some FORMAL inference intervenes, as it were, between the assertion and the conclusion should NOT be used, or useable, as an argument that this conclusion differs in meaning, in any way or sense of 'meaning' at all, from the first B assertion above: so the same informal conclusion about being an antelope that one might be justified in inferring from the comment in the first case, also applies, and in the same way and for the same reasons, in the second case. Even though the second case involves a formal inference step and the first one doesn't. There is NO implication intended here that this 'informal' inference is somehow magically made formal, or that software is supposed to be able to understand English comment strings. The point is rather to avoid an argument in the other direction, an argument that I suspect may never have even occurred to you (it hadnt to me until I got involved in this debate), along the following lines: "Formal meaning is just a mathematical curiosity and has nothing to do with Real Meanings (the kind that really Matter in Human Discourse in Society, or whatever), so whenever any formal inferences are done, the formal conclusions lose all their Real Meaning and are just mathematical curiosities of no real significance, devoid of any Real Meaning content outside some narrow abstract mathematical domain." The point of fussing over this comes from the expectation that RDF formal inference processes will in fact be involved in larger processes which are indeed social in nature at both 'ends' - such things as sending orders, making bids, deciding to buy something, giving permissions to charge to an account, that kind of thing; and to pre-empt any attempt by someone (who will be nameless but whose name is Legion) to claim that RDF/RDFS/OWL/whatever cannot be used to do this because they can only convey 'formal' meanings and this stuff is all to do with 'social' meanings, and you can't get a social meaning down a narrow formal pipe. The point being that although (of course) an RDF engine cannot be expected to understand, or have its own behavior influenced by, any meaning of any RDF it is processing beyond that specified by the model theory, nevertheless this 'other' meaning may be in a sense attached to the RDF (invisibly to the RDF engine, but still attached; and maybe visible to other entities at either end of the process) and get conveyed from one place to another intact. Here's an analogy: think of RDF as something like the post office. All it *understands* is addresses; but there can be all kinds of things inside the envelopes and packages. It doesn't need to *read* that inside stuff - for all the post office knows, the packages could all be empty - but it does get them moved from place to place. The formal meaning is the address; the social meaning is the stuff in the package. And the point is just to say that even though the stuff is inside and not mentioned explicitly in the address, it nevertheless still gets delivered. Pat -- --------------------------------------------------------------------- IHMC (850)434 8903 or (650)494 3973 home 40 South Alcaniz St. (850)202 4416 office Pensacola (850)202 4440 fax FL 32501 (850)291 0667 cell phayes@ai.uwf.edu http://www.coginst.uwf.edu/~phayes s.pam@ai.uwf.edu for spam
Received on Wednesday, 5 February 2003 14:40:09 UTC