- From: Pat Hayes <phayes@ihmc.us>
- Date: Wed, 10 Mar 2004 17:31:30 -0600
- To: "ext Jeremy Carroll" <jjc@hplb.hpl.hp.com>, "ext Pat Hayes" <phayes@ihmc.us>, "ext Patrick Stickler" <patrick.stickler@nokia.com>, "ext Chris Bizer" <chris@bizer.de>
- Cc: <www-archive@w3.org>
Ok, after more thinking. Clearly some sort of vocabulary solution would be the least painful route to take, along the lines Jeremy suggests. We have to face up to the complications it introduces, though. For example, what if an agent wants to change their mind about G, but there's an assertion out there that says that they are asserting G? What's to stop a malicious publication of assertion that A asserts P by some other agent B? What if A asserts G but then B says that G is deprecated? I think that we have to assume that there is a clear notion of the agent-thing doing the asserting, and that any asserted graph has an identifiable 'owner' who is the agent asserting it. I'm not sure how we can guarantee that this is always possible, so I'll leave that on the table as an issue. How to do it, is the question. It can't be done simply by tweaking truth-conditions (my previous gripe), so OK, we do it some other way. It will be a rather unusual semantic extension, but still a semantic extension. Lets hypothesize a class of 'RDF agents'. We don't need to say what they are exactly (RFC 2396 doesn't say what a 'resource' is exactly) but we suppose that they are resources which can perform 'web acts' with respect to RDF graphs. Web acts are 'speech acts on the Web': they include minimally asserting quoting and likely others not yet specified. Every assertion is made by an agent. Given any record of an assertion, we have to be able to figure out the agent of the assertion. Now, how does this relate to triples in graphs?? One view (1) (the one I've been using, implicitly) is that a web act is somehow connected with the publication of a graph: that the act happens when you hit the 'upload' button and something gets written on your web server. On this view, a triple in a graph would at best be a kind of noting or recording or a statement ABOUT the act, and the asserting agent is the owner of the web resource where the (original) graph is located. Another view (2), which I think Patrick is using, is that the 'act' is performed by the graph itself: that to assert *is* to have a triple of a certain kind in a graph. He wants to be sure that graphs can only assert themselves in this authoritative way, which makes sense on this view. Also, on this view, as long as asserting triples can be firmly anchored in named graphs, the locating-the-asserter problem is solved. However, I don't see how we can firmly locate triples in graphs in this way, because how can we possibly legislate against people copying triples from one graph to another? And this mixes up several things, such as the propositional nature of RDF and the distinction between a graph and a document containing the graph, that seem to be fundamental; and it muddies up RDF with things that look like locatives or indexicals ('this' or 'here') . So let me revert to the idea of a graph being a description of something, and ask what it would be describing in this case. We could say that a triple ex:agent rdfx:asserts ex:graph1 is true when the 'state of the Web' is such that ex:agent is indeed asserting, or has asserted and has not yet un-asserted, that graph. So this can come to be true and false depending on the state of the Web, which gives a model theorist nightmares but is something we have to face up to. OK so far, but this still only has the graph describing - reporting on - some event of asserting, rather than actually making anything happen. So we need a kind of web act rule (compare Grice's rules of conversational implicature :-) which says that if an agent publishes a graph which describes a web act by that very agent, then the act is deemed to have been done by that publication. That is, you cannot tell RDF lies about your own web acts. (Cannot as in 'its impossible' not as in 'its naughty') Just like in English (actually, more like in civilized English-speaking society) you cannot say "I promise..." without actually promising. I take it that this is what Jeremy meant about English doing the speech acts. However, if you say "He promises..." then unless you are empowered by him to to speak for him, eg by a power of attorney, then nobody has promised anything: which is why we need the link between the agent responsible for the triple, and the agent referred to by the triple. The weakness of this whole story is then how to establish that link between a triple and the agent responsible for it, so people can tell genuine assertings from mere descriptions of assertings. I don't have any good answer to that, but maybe we don't need to give a good answer to it, if we state the issue clearly. (Is there a good answer to the question "Who owns a web resource?") This story could be applied to either (1) or (2) above, but if with (1) there is no particular need to have the assertion be an assertion of the graph it is in. What matters is that it is an assertion BY the agent it says it is by. Its the domain rather than the range of rdfx:asserts that needs to be anchored in some kind of checkable reality. One problem seems to me to be, who is responsible for stating a general Gricean 'web act rule' like this? (Grice was the first person to describe these rules for English, but he didnt impose them, they seem to have just kind of happened.) It goes beyond the RDF or OWL semantics, which don't say anything about web actions or agency. I don't see the TAG group doing anything this formal-sounding in the forseeable future, and I don't see that we have the authority to do it. Maybe all we can do is to suggest that this might be a good way to behave and hope that the world in general listens (?) Anyway, I'll send this off and see what happens :-) 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@ihmc.us http://www.ihmc.us/users/phayes
Received on Wednesday, 10 March 2004 18:31:32 UTC