W3C home > Mailing lists > Public > www-rdf-logic@w3.org > April 2002

Why not import everything? (was: Re: getting daml:imports right is easy?)

From: Pat Hayes <phayes@ai.uwf.edu>
Date: Mon, 29 Apr 2002 09:40:46 -0700
Message-Id: <p0510154fb8ee726dd4bf@[]>
To: Drew McDermott <drew.mcdermott@yale.edu>
Cc: www-rdf-logic@w3.org
>[I'm forwarding a short interchange between Dan Connolly and me on
>the "importing" issue, with his permission.]
>From: Drew McDermott <drew.mcdermott@yale.edu>
>To: connolly@w3.org
>    I'm not sure what log:semantics is either, formally;
>    but re cyc-style lifting, see
>      Contexts: A Formalization and Some Applications
>      http://www-formal.stanford.edu/guha/guha-thesis.ps
>I really must get around to reading this.

This is about what McCarthy calls 'contexts' and what Cyc calls 
microtheories, more or less (ie there are minor differences between 
the various versions). These are handy for keeping namespaces a 
reasonable size when building large complex ontologies, but I don't 
see  that they have anything much to do with importing.

BTW there is a nice readable survey paper by Doug Lenat on how 
microtheories are used in Cyc, which (last time I looked) you can 
find by grubbing around the Cyc website.  (Im off-web so cant find 
the URI.) Doug doesn't write a lot, but when he does its worth 

>    > But, as I said on www-rdf-logic, importing an ontology just means
>    > incorporating its contents.  What's hard about that?
>    ont:imports isn't just magic syntax. It's a property
>    that relates ontology documents. It can be specialized
>    using subProperty.
>    ...
>    So Lassie is an animal; but you have to do reasoning
>    to figure out what to import from OntX.
>Well, our disagreement is clear, but, at least in part, easily
>settled.  In our view, 'imports' *is* magic syntax, and not a property
>of anything.

I agree, that is the only sensible way to look at it.  If/when we get 
around to putting something like this into the CL standard it will 
definitely be a special syntax, not a normal logical assertion. If it 
were an assertion it would have to be in a special meta-level 
concerned with ontologies as entities, and I don't think anyone wants 
to get involved with that.

However, I still wonder if we need it. Consider the admittedly naive 
assumption that anyone who uses a vocabulary is committed to using it 
the same way. Then we don't need importing: just use the same names 
is all you have to do. OK, so it is going to break down at times; but 
I bet 'imports' is going to break down at times as well, because 
people will misunderstand the intended meanings in complex 
ontologies, and so on. Seems to me that the only real purpose of 
having an 'imports' tag is to be able to NOT import some stuff you 
DONT want to agree to. So it might be more use, in fact, to have that 
as the primitive. That is, instead of having as a default that you 
might not agree with anything that you don't explicitly mention as 
imported, the SW might actually do better to base itself on the 
riskier, but more interesting, presumption that you agree with 
anything that you don't explicitly disagree with. Then engines could 
just troll around looking for content and put it together to draw 
conclusions, and could probably get a lot further than if they are 
restricted to the narrow channels of explicit import links. It will 
go wrong sometimes, but we have far harder interoperability problems 
to solve (involving genuine conceptual mismatchings), so I think a 
few simple disagreements are the least of our worries.

Q: What if my engine finds a contradiction between stuff it got from 
ontology A and ontology B? A: Well, it could just ignore them; or it 
could try to decide which of them was more likely to be right (using 
dates, maybe, or a Googlish kind of how-many-others-agree criterion) 
and maybe send them a notice telling them about the problem, if there 
was some way to do that.  Then one of them might want to change, or 
to exclude the other.

This suggests a vision of an SW which is in a constant process of 
self-repair. Imagine a kind of truth-maintenance protocol that 
allowed agents to negotiate differences of opinion. With a bit of 
care and a bit of luck, the SW might get to be more reliable in its 
opinions than the people who wrote the ontologies in the first place. 
At any rate, it could sort out sub-communities of ontologies which 
all use vocabulary terms in a consistent way. This would also, it 
occurs to me, provide some security against malicious bad-data 
ontologies which someone will almost certainly think of creating once 
the SW gets real.

Pat Hayes

IHMC					(850)434 8903   home
40 South Alcaniz St.			(850)202 4416   office
Pensacola,  FL 32501			(850)202 4440   fax
Received on Monday, 29 April 2002 12:42:27 UTC

This archive was generated by hypermail 2.3.1 : Wednesday, 2 March 2016 11:10:37 UTC