W3C home > Mailing lists > Public > www-rdf-interest@w3.org > October 2002

Re: Meaning of URIRefs

From: pat hayes <phayes@ai.uwf.edu>
Date: Fri, 25 Oct 2002 17:34:31 -0500
Message-Id: <p05111b13b9df7431143a@[]>
To: Sandro Hawke <sandro@w3.org>
Cc: www-rdf-interest@w3.org

>I need to call it a day and week

Yep, me too.

>, but let me leave with one small set
>of questions for now:
>>  Well, it seems to me that there is a simple, clear story here.
>>  1. RDF is a logic (an assertional language) , and entailment has its
>>  usual meaning.
>>  2. Urirefs 'belong' to their owners, and the owner is only
>>  responsible for the sentences hse publishes. That is, owners are not
>>  responsible for their urirefs, but they are responsible for their
>>  triples (just like everyone else.)
>>  3. In general, its good advice to only believe things published by
>>  entities you trust; but it is not logically inconsistent to be either
>>  paranoid or gullible.
>>  The only special thing that needs to be said is that
>>  4. if you publish something which uses a uriref belonging to someone
>>  else,  then it is your responsibility to ensure that the meaning you
>>  intend it to have is consistent with the meaning its owner intends it
>>  to have, ie expressed in whatever assertions hse makes using it.
>So if animals says Cat and Dog are disjoint classes, and I say _:x is
>an animal:Cat and an animal:Dog, what happens?  What does my message
>mean?  Is my message false or in some way in error?

Each message has a clear meaning, and they clearly contradict one 
another (in OWL; I presume we have moved from RDF to OWL at this 
point). So, clearly, something is wrong here. Exactly what is wrong 
isnt entirely clear. On my criteria, you have made a mistake and if I 
draw a silly conclusion from this mess, eg that the Pope is made of 
green cheese, than it can be said to be your fault. However, I didn't 
derive it just from what you said, but rather from what you said and 
what animals said.

>If I just say that _:spot is an animals:Dog, and animals (the document
>at the URI) says that Dog is a subclass of Mammal, it in no way
>follows that _:spot is an animals:Mammal?   Maybe the URI part of the
>URIRef is a strong-hint for additional content to include?

Sure, strong-hint is fine, I guess. But look: suppose you in fact 
just said something sensible about _:x, say that it was a cat and 
also a Siamese, and suppose some other schmuk said that all Siamese 
were dogs. I now have a contradiction derived from three sources. 
There's nothing you can do to protect me from believing some nonsense 
written by someone else. So no matter what *you* say, *I* need to be 
always on my toes to make sure I don't just believe anything people 
say using other people's urirefs. For that matter, I need to be on my 
toes when reading what people say about their OWN urirefs; there is 
lots of silly stuff out there which was written by its original 
authors. There are even people who think that emailboxes are human 
beings, for example.

>If some other web document (not at the animals URI) says that
>animals:Dog is a subclass of animals:Tree (disjoint from
>animals:Mammals), does the reader have any basis for thinking that
>_:spot is more legitimately an animals:Mammal than an animals:Tree?

Strict answer: no. Realistic answer: maybe, because owners of urirefs 
are more likely to take some care with what they say using those 
urirefs. Bottom line: you, the RDF reader, have to decide who you 
trust. Caveat lector.

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Received on Friday, 25 October 2002 18:34:37 UTC

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