Pat, (01)
Cassidy, Patrick J. wrote: (02)
>Actually, N^2 applies to the terms of ontologies also. The notion of
>using existing equivalence of two terms in two ontologies to reduce the
>effort of mapping might work, but only partly because:
> (1) one has to know the equivalence mapping in all the other
>ontologies -- not a trivial amount of work, and certainly not 0. If
>there are a large number of ontologies, one has to inspect the
>equivalence mappings of **every one**!! Try it, you won't like it.
>
>
Why would I have to know the equivalent mappings in all the other
ontologies? (serious question) (03)
If I trust your mapping of ontology A to ontology B, and I want to map
ontology C to B, why do I need to take the extra step of understanding A? (04)
> (2) exact equivalence of intended meaning occurs in probably less
>than half the terms in any two ontologies, and there is often meaning
>overlap which is much more work to reduce
>
>
Hmmm, so is it fair to say that at least part of the problem arises due
to the complexity of the ontologies? That is to say the more terms an
ontology covers the more difficult it is to reconcile different ontologies? (05)
> (3) *any* structural difference (difference in the relations) of two
>terms in two ontologies will make them formally different (different
>inferences) even if their intended meanings are the same.
>
>
>
So it would not be helpful in some cases to know the inferences in
different ontologies for the same terms? Granted that it would be
possible to reconcile them but what if I wanted to preserve them? (06)
> Even if it seemed to work on a very small number of ontologies, it
>is totally impractical when you get over 10. If you know of an example
>where it has been done, let us know.
>
>
>
Oh, I am not disagreeing that what you propose would be a lot of work. (07)
But it does involve the assumption that one wants to merge ontologies
that represent an entire world view (or a substantial part thereof),
which I don't doubt for a moment would be quite complicated. (08)
So if I trust a mapping of term A to term B, then would you agree that I
can map term C to B without encountering the problem you describe? (09)
Of course, the more complex the terms, that is in terms of their
relationships to other terms and permitted inferences, the more complex
the problem would become. (010)
It might well be that it would end up where you are starting with the
merging of complete ontologies. (But just beginning at a different
starting point. I will have to think about that one for a while.) (011)
Hope you are having a great day! (012)
Patrick (013)
>Pat
>
>Patrick Cassidy
>CNTR-MITRE
>260 Industrial Way West
>Eatontown NJ 07724
>Eatontown: 732-578-6340
>Cell: 908-565-4053
>pcassidy@xxxxxxxxx
>
>
>
>
>>-----Original Message-----
>>From: ontolog-forum-bounces@xxxxxxxxxxxxxxxx
>>[mailto:ontolog-forum-bounces@xxxxxxxxxxxxxxxx] On Behalf Of
>>Christopher Menzel
>>Sent: Thursday, May 03, 2007 11:09 AM
>>To: [ontolog-forum]
>>Subject: Re: [ontolog-forum] A "common basis"
>>
>>On May 3, 2007, at 5:03 AM, Patrick Durusau wrote:
>>
>>
>>>Adam,
>>>
>>>Adam Pease wrote:
>>>
>>>
>>>
>>>>Hi Chris,
>>>> Many thanks. I was really addressing a point that you weren't
>>>>making, but which is all too common.
>>>> I'm sympathetic to using SUMO for semantic interoperability.
>>>>When I've done projects in that area, it has worked well. At the
>>>>
>>>>
>
>
>
>>>>risk of stating the obvious, the advantage, at least in
>>>>
>>>>
>>theory, of
>>
>>
>>>>a common model over a federated approach is that one has mappings
>>>>
>>>>
>
>
>
>>>>linear in the number of products needing integration, rather than
>>>>
>>>>
>
>
>
>>>>potentially N^2.
>>>>
>>>>
>>>I am glad you mentioned the "potentially N^2" issue. I have seen
>>>that claim on a number of occassions but never with what I
>>>considered a convincing explanation of why it must be so.
>>>
>>>For example, assume that I have terms A, B, and C, all of which I
>>>wish to say represent the same subject.
>>>
>>>While I agree that it is possible to say A = B, A = C, B =
>>>
>>>
>>C, ....,
>>
>>
>>>isn't that an implementation choice?
>>>
>>>In other words, if I have the mapping A = B and then later add B =
>>>
>>>
>
>
>
>>>C, do I really need A = C? The effect of the first two mappings is
>>>
>>>
>
>
>
>>>sufficient to reach the desired result.
>>>
>>>Well, it should be noted that relying upon separate mappings does
>>>result in a problem Steve Newcomb has faced with his topic map
>>>implementation, that is how to determine when "all" the mappings
>>>have been performed.
>>>
>>>Ah, or is the N^2 claim based on a requirement that in order to
>>>apply whatever inferences are available at A to C, a direct
>>>
>>>
>>mapping
>>
>>
>>>is required? Still, that seems to be an implementation
>>>
>>>
>>question and
>>
>>
>>>not one of the actual mapping.
>>>
>>>That is a particular methodology of mapping is being presumed. I
>>>would assume once the mapping is complete, then the outcomes of
>>>inferencing will be the same. Yes?
>>>
>>>I have usually encountered the N^2 comment when a particular
>>>vocabulary is being advocated. Noting that an implied mapping is
>>>being peformed even by those who advocate a particular vocabulary,
>>>
>>>
>
>
>
>>>but that the implied mapping is not (usually) available for others
>>>
>>>
>
>
>
>>>to inspect or use. (The same can be the result using topic maps.
>>>There is no requirement that a mapping in an implementation, which
>>>
>>>
>
>
>
>>>may be commercial intellectual property, be disclosed. For
>>>
>>>
>>the most
>>
>>
>>>part, I think greater disclosure can potentially lead to more
>>>interoperability. But, there are tradeoffs and reasonable people
>>>will draw the line on disclosure at different places.)
>>>
>>>
>>I don't think this is the issue Adam had in mind, Patrick. I
>>believe
>>Adam's N^2 remark doesn't have anything to do with the terms in a
>>particular vocabulary (though there may in fact *be* an N^2 problem
>>of some sort lurking there), but with the number of the languages
>>used by the ontologies one is trying to integrate. Suppose we have
>>four ontologies, each one written in a separate language --
>>say Loom,
>>Classic, SNEPS, and KL-1 (chosen because I have some appropriate
>>graphics from a presentation I gave a few years ago :-) :
>>
>>
>>
>>
>
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> (014)
--
Patrick Durusau
Patrick@xxxxxxxxxxx
Chair, V1 - Text Processing: Office and Publishing Systems Interface
Co-Editor, ISO 13250, Topic Maps -- Reference Model
Member, Text Encoding Initiative Board of Directors, 2003-2005 (015)
Topic Maps: Human, not artificial, intelligence at work! (016)
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