|From:||Pat Hayes <phayes@xxxxxxx>|
|Date:||Mon, 21 Jan 2008 10:37:44 -0600|
(I apologize for the tangled appearance of this email reply: I am in an email-handler crisis which should be shortly resolved - Pat)
Re: [ontolog-forum] CL, CG, IKL and the relationship betwThe following is an attempt to summarize (and reformat in plain text) a long discussion about the context-independence of URIs so that I can respond to Pat's last response.
Originally I lamented that it was unfortunate that the W3C's architecture documents did not distinguish between the establishment of a URI and each instance of its use. My complaint was that this prevented using the context of the use of an instance of the URI when interpreting it.
PHreply> And I pointed out that the entire purpose of URIs was that they NOT be contextually sensitive, but always 'mean' the same wherever they occur, and this was not a problem or a bug, but an essential design feature, and that the Web would not work without it.
PH> The key point is, what would count as a 'context' for a
> context-dependent URI?
PH> 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.
JB>> In the following example, the differing 'contexts' are the different
web-pages upon which occurrences of a URI appear.
JB>> Your scenario is not applicable here. We need the following
>> scenario. You, sitting at your computer, use URI-A to browse
>> to an interesting web-page upon which you see a small graphic,
>> retrieved by an occurrence of URI-CD, which refers to an
>> assertion that the web-page you are viewing is written in
>> valid XHTML 1.0.
JB>> This is URI-CD: http://www.w3.org/Icons/valid-xhtml10
JB>> What this URI is intended to denote is this assertion (from the
>> W3C help page: http://validator.w3.org/docs/help.html) "To show
>> readers that one has taken some care to create an interoperable
>> Web page, a "W3C valid" badge may be displayed (here, the
>> "valid XHTML 1.0" badge) on any page that validates."
PH> The URI denotes that badge/image/web-resource/thingie.
> There is only one of it, and it, itself, is never used to make any
> assertions. The HTTP protocols supply us with a copy
> (webarch:representation) of it, and we can then use that copy
> to human:assert something about the page the copied image
> is on. OK, lets agree on all that.
PH> But notice that the [speech] 'acts' here ...<snip>... are
> intrinsically dynamic things, events that occur in time and
> within a social context (a 'web conversation', perhaps), not
> textual or even indexical entities. It is the act of displaying
> the "place order" button which constitutes the making of the
> offer, not the button itself.
PH> The name of the badge denotes the badge. USING a TOKEN of
> that badge in a certain way MAKES an assertion. But the name of
> the badge doesn't denote the assertion made with a copy of the
> badge. It also doesn't denote the web page on which the copy
> occurs, or the time of day when it was published, or a host of
> other things closely associated with it.
PH> You miss my point. I am conceding that one can use the image
> to make an assertion. My point is that the image is not identical
> with the assertional act that uses it, nor with the content that is
> expressed by such an act.
What then is the assertional act that makes this image into an assertion? Just this, I propose, a person takes the assertional act of embedding a token of that URI, "http://www.w3.org/Icons/valid-xhtml10", into her HTML page and publishing the page to the web.
And because the resulting assertion is indexical, the assertion thus made is different for each web-page that a TOKEN of that URI is embedded into. Are we still agreed?
PHreply> No. When you embed that graphic image into your web page, it is the IMAGE which has an indexical meaning, not the URI you use to get hold of the image with. That URI always has the same meaning: it refers to that one, single, image.
Now consider the word, "I", the first-person English pronoun. There is just one English word "I". Copies of it, tokens as you say, when embedded in speech or text, can be used by a speaker to denote that speaker who so embeds it. To denote (or name) that word we use a token of it, in quotes. And we say of the word named "I" that it denotes the speaker that embeds it in a sentence, that it is indexical, etc. Can't we similarly say of the URI named "http://www.w3.org/Icons/valid-xhtml10", that it denotes the assertion which is made when a web-page author takes the assertional act of embedding a token of it in his web-page, that it is indexical, etc.?
PHreply> No, because the URI does not assert anything about the user of the web page. It is not like the word "I". Your analogy here is spurious. If you were to simply type that URI into the text of your page (rather than USE it to retrieve an image) then readers of your page would not have any idea what you were intending to assert. The relationship between the URI and what it retrieves (and in this case, denotes) is nothing like the type/token distinction. For one thing, the image retrieved doesn't look at all like a URI.
You keep insisting that the URI denotes the image
PHreply> because, according to the W3C, it does. And since they own the URI and set the standards in this area, who are we to argue with them?
, but to me that would be like saying the word, "I", denotes some 16-point, black-ink image of the letter "I" on a paper page.
PHreply> No, its not like that at all. That would be saying that a type denotes one of its tokens, which indeed would be kind of silly.
To me both the black-ink "I" image and the w3c badge image are just vehicles for delivering content.
By the way, I would like to point out that some of the questions in this discussion may apply also to the ISO Common Logic (CL) specification. In the CL Requirements section 5.1.3, "Common Logic should be easy and natural for use on the Web" there is this statement, "b. URIs and URI references should be usable as names in the language". And in the "...syntax and semantics" section 6.3.1 "Importations and named phrases", where it states, "All texts which are published and identified on a network *shall* be mutually interpretable with all other texts on the network which can import them, over the same universe of reference and domain of discourse, and with their vocabularies merged."
PHreply> I don't see the relevance of this to that. As that quote makes plain, CL names are not understood indexically.
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