Patrick, (01)
[PD] > Why would I have to know the equivalent mappings in all the
other
> ontologies? (serious question)
>
> 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?
>
All I can say is "good luck". The ontologies I have seen that do a
proper job of even the most basic inheritance are rare, and if you are
willing to trust a lot of mappings without reviewing them yourself,
well, "good luck". Maybe someday there will be acknowledged
well-constructed ontologies with accurate mappings, and trustable
authoritative sources. I don't expect to live that long, and I can
think of a lot easier way to get the accurate interoperability I need. (02)
[PD] > 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?
>
No. As I said, any difference in the relational structure (which means
any difference *at all* in the ontology) will lead to different
inferences. The interoperability I want is to be able to draw the same
inferences from the same data. Mapping different ontologies won't
achieve that. If the differences are few (for the ontologies I have
seen they will be many), then differences in inferences that are
important may not show up often, like subtle bugs in a computer
program. But they will be there. If you are going to rely on your
ontology for anything really important, mapping is a way to incur great
risk. (03)
Good grief, why accept, after a great deal of effort, a product that is
known to be defective and unreliable, when there is a straightforward
way to avoid it? I don't want to play games with my ontology, I want
to be able to rely on it for important decisions. If that means
accepting a manner of representation that is not my personal
preference, well that is a very tiny price to pay for the great
benefit. (04)
Pat (05)
Patrick Cassidy
CNTR-MITRE
260 Industrial Way West
Eatontown NJ 07724
Eatontown: 732-578-6340
Cell: 908-565-4053
pcassidy@xxxxxxxxx (06)
> -----Original Message-----
> From: ontolog-forum-bounces@xxxxxxxxxxxxxxxx
> [mailto:ontolog-forum-bounces@xxxxxxxxxxxxxxxx] On Behalf Of
> Patrick Durusau
> Sent: Thursday, May 03, 2007 12:51 PM
> To: [ontolog-forum]
> Subject: Re: [ontolog-forum] A "common basis"
>
> Pat,
>
> Cassidy, Patrick J. wrote:
>
> >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)
>
> 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?
>
> > (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 (07)
> ontology covers the more difficult it is to reconcile
> different ontologies?
>
> > (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?
>
> > 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.
>
> But it does involve the assumption that one wants to merge ontologies (08)
> that represent an entire world view (or a substantial part thereof),
> which I don't doubt for a moment would be quite complicated.
>
> 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?
>
> 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.
>
> It might well be that it would end up where you are starting with the (09)
> merging of complete ontologies. (But just beginning at a different
> starting point. I will have to think about that one for a while.)
>
> Hope you are having a great day!
>
> Patrick
>
>
>
> >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 (010)
> >>>>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 (011)
> >>>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 (012)
> >>>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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> >
> >
> >
> >
> >
> >
>
> --
> 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
>
> Topic Maps: Human, not artificial, intelligence at work!
>
>
>
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> (013)
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