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Re: bags of axioms

From: Pat Hayes <phayes@ihmc.us>
Date: Thu, 1 Nov 2007 14:10:42 -0500
Message-Id: <p06230905c34fd287a20f@[]>
To: Matthew Pocock <matthew.pocock@ncl.ac.uk>
Cc: public-owl-dev@w3.org

>On Wednesday 31 October 2007, Pat Hayes wrote:
>>  >Hi,
>>  >Through having logical and physical URIs, the ontology elements are making
>>  >some sort of statement that they are a recognisable set of axioms, that
>>  > exist for some purpose, and so on.
>>  ? Why? This seems like wrong thinking to me. First, there's no
>>  distinction between 'logical and physical' URIs, so lets just talk
>>  about URIs. Think of a URI as a name. Giving a name to something is
>>  just making a statement that it can be referred to, is all. And that
>>  hardly amounts to saying anything about it. Google queries are
>>  evanescent things that have no location, but they are encoded as URIs.
>Granted. This is perhaps more an issue of resolvable vs non-resolvable URIs,
>and the mechanisms used to turn logical URIs into physical URIs etc. that we
>all have to deal with in some way. Probably off-topic.
>Regards the "Giving a name to something is just making a statement that it can
>be referred to" is exactly what we don't want to do - these bags of axioms
>shouldn't be refered to, they should just be moved about and absorbed by
>software agents. They are transient in existence.

Well, OK, but I guess I still don't see why being transient means you 
can't refer to it. I can refer to a lightning stroke. You seem to be 
giving more weight to the idea of naming something than it deserves 
to have.

But if you were to just say, it doesn't NEED to be given a name, then 
OK, I take your point.

>  > >b) have no logical URI that identifies them, or any other identifier
>>  > smaller than themselves
>>  Don't have in fact, or can't have because you don't want to ever give
>>  them one? If the latter, why not?
>It simply does not exist. These are anonymous bags of axioms. They do not
>exist outside of the communication transaction. They should never be refered
>to outside of the communication transaction.

That is, they don't need to have a name. OK, but now Im rather 
puzzled as to why you are concerned about these things at all. Why 
have an ontology which talks about entities that can never be 
referred to? What use is this ontology going to be? How will it have 
any consequences for your system?

>  > >c) are a sub-set of the axioms entailed by some other ontology, which does
>>  >have a logical URI
>>  >
>>  >Is there some other top-level element other than Ontology that better
>>  > fulfills these needs?
>>  Whats wrong with Ontology? Nothing you have said is inconsistent with
>>  these things being in the class Ontology.
>Well, OWL/XML requires a URI attribute on the ontology element for a start.

Oh, good point, I had forgotten that. Fair enough, that does seem 
like a mistake now you point it out.

>Also, all of the tools we have looked at require the ontology to have a URI.
>>  They don't HAVE to have a
>>  URI, you could refer to them with Bnodes. But in fact it is a very
>>  low-cost business to construct a unique URI, rather like gensym in
>>  GOFLISP. Use, say, the base URI of the derived-from ontology and
>>  append the real time in seconds the thing was streamed. Or whatever.
>>  Of course if you try to GET or owl:import that URI things will break.
>>  So, don't.
>In practice, this is close to what we do actually do. However, it feels ugly
>and dirty to be minting URIs that serve no purpose other than to get a file
>to validate, and which no software should ever use in any way for a bag of
>axioms that where only packaged together for transmission purposes.
>>  >If not, is there some standard way to indicate to tools that the ontology
>>  > has no physical or logical URI, but is a) a sub-set of the axioms in
>>  > another ontology or b) the axioms entailed by another ontology or c) a
>>  > sub-set of the axioms entailed by another ontology?
>>  Not a standard, but you could invent this subclass of Ontology if you
>>  want, call them EvanescentOntologies or something.
>Ah, yet more non-standard solutions :) Don't we all love forks.

Well, OK, but you can't expect any standard to predict in advance all 
the entities that anyone is ever going to want to describe. Seems to 
me that if you are the first to run into this, then if you write a 
really neat ontology of them and publicize it, other people will use 
your solution and it will become a de facto standard. At any rate, 
its a much less painful process than trying to convene a Working 
Group and getting it to recommendation.


PS. This is a highly nonstandard and heretical suggestion, but if you 
really are NEVER going to refer to any of these things, then maybe 
you can just use the same URI over and over again for all of them. 
That's even lower cost, and it might work (I havnt checked or even 
thought it through carefully.) Think of it as a bare plug used to 
fill the URI attribute socket.

>>  Pat

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Received on Thursday, 1 November 2007 21:11:03 GMT

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