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Re: [ontolog-forum] CL, CG, IKL and the relationship between symbols in

To: Duane Nickull <dnickull@xxxxxxxxx>
Cc: "[ontolog-forum] " <ontolog-forum@xxxxxxxxxxxxxxxx>
From: Pat Hayes <phayes@xxxxxxx>
Date: Fri, 28 Dec 2007 19:17:45 -0800
Message-id: <p06230902c39b6b7c3a7b@[]>
>You may want to read Roy Fieldings thesis....
>REST?    (01)

Ive read it, of course. But yes, it is a 
foundational work for the TAG view of Web 
architecture. On the other hand, the real point 
of http-range-14 is not to re-write REST, but to 
align the REST ideas with the SWeb ideas of 
reference and denotation and description (none of 
which play any role in REST). Also, for those 
embarking on this voyage, it is vitally important 
to keep in mind that both Fielding's thesis and 
the W3C TAG use words like 'representation', 
'identify' and 'resource' in highly idiosyncratic 
ways which do not correspond to their uses in KR 
and ontology work, or indeed to normal English. 
It has become commonplace in email debates (see 
the archived W3C TAG discussions for example) to 
distinguish 'representation', 
'webarch:representation'and 'rest:representation' 
to try to keep the various meanings clear.    (02)

Pat    (03)

>On 12/28/07 6:50 PM, "Pat Hayes" <phayes@xxxxxxx> wrote:
>>>  on Fri. Dec. 28, 2007 at 5:31 PM, Pat Hayes wrote:
>>>>>  on Wed. Dec. 26, 2007 at 7:30 PM, Pat Hayes wrote:
>>>>>  [snip]
>>>>>  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
>>>>>>  contexts'.
>>>>>  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
>>>>  Laputa.
>>>>  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
>>  endpoint.
>>>  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
>>>>>  purpose,
>>>>  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
>>  people.
>>>  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.
>>  Pat
>>>>  Pat
>>>>>  (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
>>>>>  www.kashori.com
>>>>  --
>>>>  ---------------------------------------------------------------------
>>>>  IHMC (850)434 8903 or (650)494 3973   home
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>  >>> phayesAT-SIGNihmc.us       http://www.ihmc.us/users/phayes
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>    (04)

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    (05)

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