- From: Rikkert Koppes <rikkert@finalist.com>
- Date: Wed, 13 Jun 2007 11:42:30 +0200
- To: Richard Cyganiak <richard@cyganiak.de>
- CC: Pat Hayes <phayes@ihmc.us>, Sandro Hawke <sandro@w3.org>, semantic-web@w3.org
What you do is wrong, it was my problem as well. You just can't use the same identifier as both you and your webpage. You should do something like: <http://richard.cyganiak.de/#me> a foaf:Person . <http://ontoworld.org/wiki/Richard_Cyganiak#me> a foaf:Person Rikkert Koppes (mophor) Richard Cyganiak wrote: > > > On 12 Jun 2007, at 22:07, Pat Hayes wrote: >>> To pick up just one point: Where do you draw the line between >>> harmful punning and efficiency-increasing punning? Any rules of >>> thumb for when it is OK? Why is it OK to pun with email addresses, >>> but not with wives? >> >> Because people and email addresses are so different that almost >> nothing you ever want to say about or do to one is ever said about or >> done to the other. If you email to PatHayes, you must have meant to >> PatHayes' email address. If you assert that my email address has two >> children, you must have meant me. With two people (or two mailboxes) >> however, things are different. There really is no way to tell then >> which is meant: you can't locally disambiguate the punning. > > Here are two web pages about me: > > <http://richard.cyganiak.de/> > <http://ontoworld.org/wiki/Richard_Cyganiak> > > One is in German, the other in English: > > <http://richard.cyganiak.de/> dc:language "de" . > <http://ontoworld.org/wiki/Richard_Cyganiak> dc:language "en" . > > You say it's OK to use a web page URL to denote the person it's about, > so: > > <http://richard.cyganiak.de/> a foaf:Person . > <http://ontoworld.org/wiki/Richard_Cyganiak> a foaf:Person . > > Both clearly denote the same person, so we can confidently state: > > <http://richard.cyganiak.de/> > owl:sameAs <http://ontoworld.org/wiki/Richard_Cyganiak> . > > This allows us to conclude: > > <http://richard.cyganiak.de/> dc:language "de" . > <http://richard.cyganiak.de/> dc:language "en" . > > Which is obviously wrong. So what did I do? > > 1. I used the DC, FOAF, and OWL vocabulary, which are used in exactly > this way all over the Semantic Web. > 2. I used an inference rule sanctioned by the OWL specifications, > which is used all over the Semantic Web. > 3. I used your claim that punning is OK. > > And I arrived at an incorrect conclusion. Why, Pat? > >> So the rule of thumb, which can be made operationally quite precise, >> is that punning is OK if (there is a very high probability that) >> there is enough contextual information available at the point of use >> to figure out which of the various meanings is intended. > > I think on the open Semantic Web, there is a very high probability > that your URI will end up in places where that contextual information > is not available and thus the information consumer cannot figure out > which of the various meanings was intended. It seems to me that, > following your own guideline, we'd have to conclude that punning on > the Semantic Web is almost never OK. > > Richard > > >> >> Pat >> >>> >>> Cheers, >>> Richard >>> >>> >>>> But the appropriate thing to say is not to denigrate punning, but >>>> to explain what is wrong with doing it badly. >>>> >>>>> >>>>>> And what about a URI >>>>> > that I own and wish it to denote, say, the planet >>>>>> Venus, or my pet cat? What do I do, to attach the >>>>>> URI to my intended referent for it? >>>>> >>>>> You publish a document (an ontology) so it's available through >>>>> that URI. >>>>> If it's a hash URI, you publish the ontology at the non-hash version. >>>>> If it's a slash URI, you publish the ontology at the far end of a 303 >>>>> redirect. And you content-negotiate HTML and RDF. >>>>> >>>>> So when users paste that URI into their browser, they get the >>>>> official >>>>> documentation about it. >>>> >>>> None of that attaches a URI to my cat (though see below) >>>> >>>>> And when RDF software dereferences that URI, it gets some logical >>>>> formulas which should be understood (like the HTML) to be asserted >>>>> by the >>>>> URI's owner/host/publisher. Those formulas constrain the possible >>>>> meanings of that URI, relative to other URIs. >>>> >>>> Neither does any of that (and in this case, I can *prove* it, using >>>> Herbrand's theorem.) >>>> >>>>> They can't nail a URI to >>>>> Venus >>>> >>>> Quite. In fact, none of this can nail a URI to ANYTHING other than >>>> something accessible using a transfer protocol. >>>> >>>>> , but they can use other ontologies to provide useful (and possibly >>>>> very constraining) information, like that it's an astronomical >>>>> body with >>>>> a mass of about 5e+24kg. >>>> >>>> You are begging the question. Suppose an ontology asserts >>>> >>>> ex:Venus rdf:type ex:AstronomicalBody . >>>> >>>> Now, what ties that object URI to the actual concept of being an >>>> astronomical body? And so on for all the other URIs in all the >>>> other OWL/RDF ontologies. The best you can do is to appeal to the >>>> power of model theory to sufficiently constrain the interpretations >>>> of the entire global Web of formalized information. But that >>>> argument from Herbrand's theorem (basically, if it has a model at >>>> all then it has one made entirely of symbols) applies just as well >>>> no matter how large the ontology is. >>>> >>>> The only way out of this is to somewhere appeal to a use of the >>>> symbolic names - in this case, the IRIs or URIrefs - outside the >>>> formalism itself, a use that somehow 'anchors' or 'grounds' them >>>> to the real world they are supposed to refer to. If we all assume >>>> that English words are so grounded (not a bad assumption) then this >>>> can be done in principle by using the URI in English sentences or >>>> to other kinds of representation which are widely accepted as >>>> real-world identifiers, like SS numbers or facial images. I did all >>>> three in >>>> >>>> http://www.ihmc.us/users/phayes/PatHayes.html >>>> >>>> If the TAG said this somewhere, and recommended how to do it, that >>>> would be great. >>>> >>>>> >>>>> My advice here is, I confess, not widely followed. But I hear >>>>> more and >>>>> more people converging on the idea that this is both practical and >>>>> likely to be sufficiently effective. >>>> >>>> I agree. Still, its important to describe it properly. It doesn't >>>> mean that URIs have a unique denotation. >>>> >>>>> >>>>>> The point surely is that URIs used to refer (not >>>>>> as in HTTP, but as in OWL) do *not* have a >>>>>> standardized meaning. Standards are certainly a >>>>>> chore to create, but they only go so far. OWL >>>>>> defines the meanings of the OWL namespace, but it >>>>>> does not define the meanings of the FOAF >>>>>> vocabulary, >>>>> >>>>> No, that's up to the owner(s) of the FOAF terms. >>>>> >>>>>> or the URIrefs used in, say, >>>>>> ontologies published by the NIH or by JPL. >>>>> >>>>> And that's up to the NIH and JPL, respectively. >>>> >>>> I understand that. I was reacting to Tim's comments, which seemed >>>> to suggest that all this should be determined by standards-setting >>>> groups. >>>> >>>>> >>>>>> The >>>>>> only way those meanings can be specified is by >>>>>> writing ontologies: and finite ontologies do not >>>>>> - cannot possibly - nail down referents >>>>>> *uniquely*. >>>>> >>>>> Ah -- there we go. There must be a long history of this subject in >>>>> philosophy. Can things ever be nailed down uniquely? I haven't a >>>>> clue. >>>>> But that's the wrong question. >>>> >>>> Surely this is exactly the question. I didn't raise the issue, Tim >>>> did. There is a claim, often repeated and sometimes cited as >>>> doctrine, that a URI *must* identify a *single* referent. To do >>>> this requires that things are nailed down uniquely (isn't that >>>> EXACTLY what it says?) but they can't be. >>>> >>>>> In this thread, I don't think we're >>>>> talking about whether we can really be sure what we mean when we say >>>>> such a URI denotes Venus. >>>> >>>> Well then don't SAY that is what you are concerned with, for >>>> goodness's sake. That is what is implied by "the URI for Venus has >>>> a unique denotation". >>>> >>>>> Instead, we're talking about whether it's a >>>>> good practice to use a single URI to denote clearly distinct things >>>> >>>> Aaaaargh. What do you think is 'clearly' distinct? >>>> >>>> The second rock from the sun might be a continuant or an occurrent. >>>> Those are as clearly distinct as a rock and a Roman goddess. I know >>>> people are a lot more familiar with the second kind of clearly >>>> distinct, but ontologies aren't people. And the first kind of >>>> difference is more important, if anything, than the second, for an >>>> ontology. The second kind of muddle is easily resolved. The first >>>> kind can be fatal. >>>> >>>>> , >>>>> such as: >>>>> (1) the second rock from the sun >>>>> (2) the Roman goddess of love >>>>> (3) a star tennis player >>>>> (4) ... etc >>>>> The term "ambiguity" covers both these issues, but we don't need to >>>>> combine them. >>>> >>>> Well, you tell me how to distinguish them, then. >>>> >>>>> The first is a kind of imprecision, a fuzziness >>>> >>>> No, its worse than that. Its like the distinction between an object >>>> and a process. Fuzziness/imprecision is what gives you the >>>> 'Everest' kind of examples. >>>> >>>>> , while >>>>> the second is the re-use of a word for a second meaning, a homonym. >>>>> (Homonyms seem to be called "overloading" in computer programming.) >>>>> >>>>> I think we know how to work with homonyms, but since we're >>>>> engineering a >>>>> new system, it seems like a good design decision to forbid them, >>>>> doesn't >>>>> it? >>>> >>>> Well, actually, no. Overloading is widely used for good engineering >>>> reasons. And on an open system like the Web, we arent going to be >>>> able to prevent it happening, so we will need to have methods of >>>> dealing with it. Once those are deployed, one might as well take >>>> advantage of them. Making grand statements about what should be >>>> done seems to me like trying to tell evolution what it ought to be >>>> doing. >>>> >>>> Pat >>>> -- >>>> --------------------------------------------------------------------- >>>> IHMC (850)434 8903 or (650)494 3973 home >>>> 40 South Alcaniz St. (850)202 4416 office >>>> Pensacola (850)202 4440 fax >>>> FL 32502 (850)291 0667 cell >>>> phayesAT-SIGNihmc.us http://www.ihmc.us/users/phayes >> >> >> -- >> --------------------------------------------------------------------- >> IHMC (850)434 8903 or (650)494 3973 home >> 40 South Alcaniz St. (850)202 4416 office >> Pensacola (850)202 4440 fax >> FL 32502 (850)291 0667 cell >> phayesAT-SIGNihmc.us http://www.ihmc.us/users/phayes >> >> > >
Received on Wednesday, 13 June 2007 09:42:33 UTC