Pat Hayes wrote:
>> Pat Hayes wrote:
>>>> Re: Peter F Brown's post (Sat, 14 Apr 2007 09:35:14)
>>>>
>>>> Peter writes:
>>>>
>>>> "
>>>> The spec is clear, yesS. but an object is not the same thing as the
>>>> address of the object - (according to the RFC, I *am* my address): the
>>>> object needs identity as much as the address of it does. That is
>>>> where I
>>>> feel this axiom of the W3C falls downS
>>>> "
>>>>
>>>> Clearly there is a problem here. But we should be careful to
>>>> distinguish confusedly designed frameworks from confused documentation
>>>> of well-designed ones.
>>>>
>>>> While RDF specifications, for example, are relatively clear and sound,
>>>> the RDF primer provides an abundance of examples such as:
>>>>
>>>> ex:index.html exterms:creation-date "August 16, 1999" .
>>>> ex:index.html dc:language "en" .
>>>>
>>>> supposed to state that "August 16, 1999" is the creation date of a page
>>>> and "en" is he language of a page, while both are literal strings and
>>>> *not* identifiers for a date and a language, respectively.
>>>
>>> What?? Why should a string not be an identifier? In fact, it seems
>>> to me that *all* identifiers are strings. And the second example uses
>>> a language tag which is taken from an Internet standard for language
>>> tagging: what could be a better example of an agreed identifier? Why
>>> is this confused?
>>
>> Hold on. It is not whether something is a string or not which counts,
>> but how it is to be interpreted. Of course, "August 16" can be an
>> identifier for anything you may wish. But it is a string, not a date.
>
> It *is* a string, of course. It *identifies* a date. You said it was not
> an identifier, not that it was not a date. (01)
Yes, and I said that because this follows from RDF specs. A literal
string appearing as the object of a triple is treated as a literal, i.e,
as a self-referential entity, rather than an identifier for some other
entity. In this context, "August 16" is not an identifier for a date,
it is an identifier for itself. Is this better? (02)
>
>> But as the object of a triple, "August 16" is a literal, not a URI,
>> and in RDF, a literal is (supposed to be) self-referential.
>
> Plain literals, yes. It would indeed be better practice to have the
> object of that triple be a typed literal. But this is an example from
> the *primer*; one step at a time.
>
>> Thus, the denotation of "August 16" is "August 16", not a date. Thus,
>>
>> <u1> <u2> "August 16"
>>
>> effectively means that the denotation of u1 is in the denotation of
>> u2-relation with "August 16" (the string), not with a date.
>
> But that string can be interpreted as denoting a date, using widely used
> conventions for denoting dates. So this is a perfectly valid RDF
> extension, speaking strictly, where 'extra' semantic conditions are
> imposed (in this case, that the date-string is interpreted
> conventionally). We anticipated that RDF would be widely used with such
> conventions added. (03)
Can't see how this would be a good practice; for a dumb machine, you
leave the question: is "August 16" supposed to identify a date (or
whatever else), or is it supposed to identify "August 16"? (04)
While in this case you might use the range of the relation as a
guidance, it may not always be so easy. Consider the case: (05)
<text-uri> <contains-relation-uri> "the text 'hello'" (06)
Now, is "the text 'hello'" (replace single quotes with escaped double
quotes if preferable) an identifier for "the text 'hello'" or for
"hello"? It won't help that (the referent of) contains-relation-uri has
the type 'string' as its range. (07)
My point is, it seems far better to say that a literal is
self-referential rather than that it may or may not be, depending on
some unspecified context. (08)
vQ (09)
>
> Pat
>
>
>>
>>>
>>>> But from
>>>> this apparently confused example one should not infer that RDF
>>>> itself is
>>>> confused (in this respect).
>>>>
>>>> (This is not to say that RDF is not confused.)
>>>
>>> One can make many valid criticisms of RDF, but being confused isn't
>>> one of them.
>>
>> I did not say that RDF was confused either. I just said I hadn't said
>> it were.
>>
>> vQ
>>
>>>
>>> Pat
>>>
>>>>
>>>>
>>>> Wacek
>>>>
>>>>
>>>>
>>>> --
>>>> Wacek Kusnierczyk
>>>>
>>>> ------------------------------------------------------
>>>> Department of Information and Computer Science (IDI)
>>>> Norwegian University of Science and Technology (NTNU)
>>>> Sem Saelandsv. 7-9
>>>> 7027 Trondheim
>>>> Norway
>>>>
>>>> tel. 0047 73591875
>>>> fax 0047 73594466
>>>> ------------------------------------------------------
>>>>
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>>>
>>>
>>
>> --
>> Wacek Kusnierczyk
>>
>> ------------------------------------------------------
>> Department of Information and Computer Science (IDI)
>> Norwegian University of Science and Technology (NTNU)
>> Sem Saelandsv. 7-9
>> 7027 Trondheim
>> Norway
>>
>> tel. 0047 73591875
>> fax 0047 73594466
>> ------------------------------------------------------
>
> (010)
--
Wacek Kusnierczyk (011)
------------------------------------------------------
Department of Information and Computer Science (IDI)
Norwegian University of Science and Technology (NTNU)
Sem Saelandsv. 7-9
7027 Trondheim
Norway (012)
tel. 0047 73591875
fax 0047 73594466
------------------------------------------------------ (013)
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