You may want to read Roy Fieldings thesis.... (02)
On 12/28/07 6:50 PM, "Pat Hayes" <phayes@xxxxxxx> wrote: (05)
>> on Fri. Dec. 28, 2007 at 5:31 PM, Pat Hayes wrote:
>>>> on Wed. Dec. 26, 2007 at 7:30 PM, Pat Hayes wrote:
>>>> JB>>Reminds me of a question I keep having with regard to URIs in the
>>>>>> Web Architecture. There doesn't seem to be any attempt to
>>>>>> distinguish between each occurrence (I sometimes call it an
>>>>>> utterance) of a URI and its establishment.
>>>> PH> Indeed, there is not. On the contrary, there is an insistence that no
>>>>> such distinction be made. To make it is an architectural error.
>>>>> That is the whole point of URIs, if you think about what they are
>>>>> mostly used for. If your browser, in its context, were to
>>>>> interpret a URI differently from the website it identifies, in
>>>>> its context, then the entire Web would stop working.
>>>>>> And in fact, it seems to be argued often that this is by design
>>>>>> and intentional, yet nowhere is are there methods for dealing
>>>>>> with what seems to be inevitable contextual differences between
>>>>>> each occurrence of a URI.
>>>>> That is exactly the point. There should not be any such
>>>>> contextual differences. The CL logic is designed to eliminate
>>>>> them. If they, as you say, 'inevitable', then the Web must be
>>>>> broken. But on the whole it seems to work reasonably well.
>>>>>> In other words, it sounds like IKL aims for the same goal
>>>>> IKL and CL are similar in this aspect, of having globally
>>>>> transparent meanings for names.
>>>>>> but includes some machinery for achieving it, while the Web
>>>>>> Architecture claims that it is so by engineering design.
>>>>> Well, URIs on the Web have a dual aspect: they provide access to
>>>>> "information resources" (for the meaning of this jargon, go to
>>>>> the W3C) and they also are used in RDF and OWL to *denote*
>>>>> arbitrary things. The relationships between these two roles are
>>>>> subtle and controversial, and not always described very clearly.
>>>>> But certainly, both the Web architecture and the CL logic assume
>>>>> that names denote uniformly, not differently in different 'local
>>>> I just came across this in Tarski's 1944 paper, The Semantic
>>>> Conception of Truth: "...the fundamental conventions regarding
>>>> the use of any language require that in any utterance we make
>>>> about an object it is the name of the object which must be
>>>> employed, and not the object itself. In consequence, if we wish to
>>>> say something about a sentence, for example, that it is true, we
>>>> must use the name of this sentence, and not the sentence itself."
>>> Quite. The same basic point was made much earlier, and more
>>> humorously, by Johnathan Swift, in his description of the isle of
>>> But this is not *strictly* true in human discourse. If there is
>>> some way to indicate the actual object without naming it, for
>>> example by pointing to it or brandishing it or looking pointedly at
>>> it, I can refer to a thing without naming it. We do this all the
>>> time. For example, I might pick up a vegetable in a supermarket and
>>> say to you, "Rutabaga?", using the vegetable itself as the object
>>> of my query. However, this can only be done in a setting where both
>>> you and I and the thing itself are equally part of the immediate
>>> common ground.
>> I believe this is true of web objects. If I mention a URL to you
>> then both of us can use HTTP to access the same object at nearly the
>> same time.
>>>> This reminds me of my objection (due partly to my understanding
>>>> of your own arguments about it) to the current attempts to
>>>> describe the relationship between those two roles. For I think the
>>>> same could be said about the object that is accessed by using a
>>>> URI utterance in an HTTP system. To say of a web document that it
>>>> is an information resource, for example, it is the name of the
>>>> object (the URI) which must be employed, and not the object
>>>> itself. What the current version of the web architecture seems to
>>>> be saying is that web objects, as opposed to everything else, say
>>>> what they are themselves.
>>> It would be more accurate to say that they respond in a
>>> characteristic way to a certain kind of action. If you stroke
>>> something and it purrs, you conclude it was a cat: but that doesn't
>>> mean that the cat itself is referring to anything. And even if it
>>> did, the purr itself can be viewed just as much a name as "cat" is.
>>> Similarly, the http response code is a symbolic signal emitted by
>>> the resource itself. In fact, given that the TAG ruling is that in
>>> this case, the URI refers to the resource, the situation is very
>>> similar to my calling your name while addressing a crowd, and you
>>> responding "yes, I'm here". Notice that this has you referring to
>>> you by using "I".
>> Perhaps this is so, but how will this make it into RDF or OWL?
> It already is in RDF and OWL. That is, these languages presume that
> URIs denote things. There is currently some ambiguity about what
> exactly a plain URI (without a # extension) should denote: the
> current recommendation is that when that URI returns a 200 response
> to an HTTP GET, then it denotes the web resource at that http
>> Doesn't this require that axioms be added to the specification?
> No. Axioms wouldn't be enough to stipulate this.
>> Doesn't this make it a special case?
> Well, yes, but its a very very common special case.
>> With that ruling, a large set of URI must be understood to be
>> members of the class "Information Resource"
> Not the URI, but what the URI denotes. Yes, almost all of them, in
> fact. But almost all extant URIs ARE being used to identify websites
> and web pages, so this has the merit of not requiring the entire Web
> to be re-engineered to suit RDF.
>> and furthermore, that class must be understood to be disjoint with
>> all sorts of other classes.
>>>> In other words, to make utterances about a web object, you use the
>>>> web object itself (including the 200 OK), and not its name.
>>> No, you *use* the URI that accessed that web object, to also talk
>>> about it (eg in RDF or OWL)
>>>> This would be like insisting that, when talking about a car, you
>>>> had to insert the car itself in your speech somehow, as the
>>>> subject of all propositions about it. This, of course, would seem
>>>> to have the great advantage that everyone would always be
>>>> referring to the same car - unambiguously - regardless of any
>>>> local context. But actually, I think this is an illusion. Objects
>>>> can't insert themselves into ontological categories. Agents use
>>>> names to put categories around objects like cars or web documents
>>>> for particular purposes. The universe just exists, agents say what
>>>> objects are by using language.
>>> Quite. But this is irrelevant to the point we were discussing.
>>>> So I don't agree it would break the web for each utterance of the
>>>> name (URI occurrence) of some web object to be used for any useful
>>> BUt wait, you have begged the question already. To say that a name
>>> is the name OF a given thing is to presume that all occurrences of
>>> that name are names of that one thing. WHich is exactly the point
>>> at issue. If names can change their referents on every occurrence,
>>> then the very notion of a "name of a thing" ceases to be meaningful.
>> I see what you mean about saying "...name of some web object...",
>> but it looks like I begged the question by assuming what I am
>> disputing! more like self-destructing than begging.... On the other
>> hand, I thought by hedging with "useful" I avoided such cases of
>> extreme variability as would render it meaningless - oh well.
> The problem is that machines have no grasp of nuances like "useful",
> and this discussion is about conventions for machines to use, not
>> But seriously, I feel like I must be missing something again about
>> names and contexts. Here is the problem. My name is "John", a good
>> proper name, which in the presence of my immediate family, nails me
>> precisely, and very efficiently. In another family, occurrences of
>> the same name, "John", refer equally well to other referents, with
>> equal precision and efficiency. This use of the term "context"
>> appears to me very trivial and ubiquitous.
> Ubiquitous, but not at all trivial.
>> Isn't this type of context the same as a "namespace" that occurs
>> frequently in programming languages?
> Not really.
>> It permits names to change their referents, if not on *every*
>> occurrence, at least on every change of context (or namespace). Or
>> am I missing something?
> The key point is, what would count as a 'context' for a
> context-dependent URI? Consider this scenario. You, sitting at your
> computer, use a URi to browse an interesting website, and you send me
> an email telling me about it and citing the URI. I then, sitting at
> my computer, two days later on the other side of the planet, type
> that URI into my browser. We expect that we will see the same
> website: but what do our two contexts have in common? It might be
> almost nothing: the times, places, browsers, countries, users, OSs,
> maybe even cultural and linguistic settings, can be completely
> different. It is inherent to the Web that the contexts of publication
> and of use of a URI can be arbitrarily different and far apart on
> every dimension, yet the URI is supposed to retain its meaning.
>>>> even if different from other uses, all while HTTP returns the same
>>>> object for the same URI.
>>> Here you touch on a delicate point. IMO, there is indeed an
>>> important conceptual distinction to be made between the
>>> relationships of naming or reference, on the one hand, and
>>> 'accessing' or 'identifying' on the other, and many of the W3C
>>> discussions fail to make this distinction and so are hopelessly
>>> muddled. The http-range-14 decision can be summarized as: when a
>>> Web object returns a 200 response code, the URI which accessed it
>>> (ie the GETing of which resulted in the code being returned) must
>>> also be understood as denoting it. This is highly intuitive, so
>>> much so that many folk take it as so obvious as to not need saying,
>>> but it does need to be said, as it is by no means necessary.
>> And again, doesn't it need to be pounded into RDF and OWL somehow?
> Thats exactly what the http-range-14 decision is trying to do.
>>>> (But even as I try to wrap this up and hit the send button, I see
>>>> problems with this. For example, the fly (object) buzzing around
>>>> in front of the frog reflects light that physical changes the
>>>> frogs vision transducers in a distinct, fly-like way. When the
>>>> frog processes this as a fly, that is, when the frog's brain puts
>>>> it in the 'dinner' category, it appears very much like it is the
>>>> very essence of the fly, the fly's fly-ness that does so. Any frog
>>>> that arbitrarily put it in the 'mate' category, for example, would
>>>> lead a very short life.)
>>>> John Black
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