Proposed issue: What does using an URI require of me and my software?

I'm trying to frame this as a reasonable crisp issue so we can knock it 
off our plates.
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KEY TEXT:

From: http://lists.w3.org/Archives/Public/www-tag/2003Jul/0022.html

"""3) There may be some need to clarify frequent misunderstandings by
making some things clear.

-  the architecture is that a single meaning is given to each URI (such
as P), that the URI ownership system makes statements by owners
authoritative weight, despite what other documents may say.
- the architecture does not permit the meaning of a URI to be changes
by consistent misuse by others.
- that use of a URI in RDF implies a commitment to its ontology, and if
there is doubt as to what ontology that is, the web may be used to
resolve it.
- that the web is not the final arbiter of meaning, because URI
ownership is primary, and the lookup system of HTTP is though important
secondary. (That is, if you hack a web server's ontology files, you do
not change hat the URI means, you just break a machine for a while)
- etc etc."""

The main line is "that use of a URI in RDF implies a commitment to its 
ontology".

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AN INTERPRETATION

I interpret "implies" and "commitment" strongly. I.e., I don't see it 
captures the meaning of this claim to say, "use of a URI in RDF suggest 
that checking out the ontology might be helpful".

So, to make the claim starker, I rewrite thusly:

	"use of a URI in RDF commits you to its (owner's) ontology"

(Thus far we have no account of whether it's only using a URI 
"assertionally" or even "without scare quotes" that so commits. Given 
that RDF has neither non-assertional modes nor scare quotes, it may be 
moot. I am curious, however, about the status of URIs in literals!!!)

So, the question arises: What does commitment require of me? It seems 
to me that commitment to an ontology, minimally, as a necessary 
condition, requires my importing that ontology into my document. How 
could it not? Really? Oh, an my *only* importing/using that ontology. 
There may be some fine cases where I can nuance a bit, but it seems 
like being committed to someone's ontology requires that I say no less 
than what they said, and I only say more in a variety of compatible 
wasy.

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TECHNICAL POINT

This resolves to a simple technical point: Should an RDF 
processor/reasoner/agent import, to the best of its ability, pace 
network outages, cacheing, etc. "the" ontology of every URI it sees in 
a document? There *is software that made this assumption*. In our 
group, a student wrote an editor, RIC, that did exactly this. DanC and 
Tim, at the WWW BOF, I'm pretty sure, said that this was what you *had* 
to do. DanC said, I believe, that all his software already did that.

I'm not against software doing that. I'm against the spec requiring it.

There are various attempts to "limit the damage" by saying that you 
only have to do this for "predicate uris", or for "declared 
namespaces". All of these, in principle I think, grant that some sort 
of document authorial control over imports is required. I want rather a 
lot for the author. That someone's software tells me "Oh, look, they 
changed their ontology, you're no longer compatible with what they said 
in the defining ontology" is fine and useful. But I don't think *THAT 
SOFTWARE* gets to tell me that my use of the URI is now bound by the 
changed ontology.

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PROCEDURAL POINT

I don't see how this is a matter for Web Architecture rather than the 
working groups. Not all uses of URIs entail inclusion of the document 
the URI points to, even in HTML. For example, <a 
href="...someImage.jpg">...</a> vs. <img src="...soemImage.jpg"/>.

There is already evidence that the working groups and the community 
have been wrestling with this technical point. See the debates about 
owl:imports. I contend that there is no consensus about which control 
mechanism is best, but that there is rough consensus that *some* sort 
of control mechanism is needed.

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RED HERRINGS

Retrievability is a total red herring. Much of Tim's language above 
seems devoted to weakening the requirement that you look up the 
ontology each time. That weakening just doesn't do anything for me. The 
requirement is commitment to the URI owner's ontology, and, apparently, 
to the current URI owners *current* ontology (which I must try to 
ascertain to the best of my ability, and we're tolerant of web 
failures, etc.)

Natural language defintions. These are related but distinct. But let me 
tell you, if you think I'm committed to not only the *formal, machine 
readable* ontologies (in an importy sense) but the *natural language* 
ontologies...uh...well, let's just say I don't know how to import the 
latter. (Actually, this would suggest that I, a software writer, would 
have to check EVERY URI for the natural language spec and rewrite my 
software to conform. Yick.)

Cheers,
Bijan Parsia.

Received on Tuesday, 23 September 2003 11:00:55 UTC