Bijans quibbles are all quite correct, but I plead that I was trying to get
across a basic almost sociological divide here (and was talking to logicians)
and there wasnt time to go into too much detail. He is also quite right that
OWL2 refers to "axioms", a fact I had simply forgotten. Its unusual, though, in
this respect. Calling them axioms is by no means, um, axiomatic. (01)
One counter-quibble: (02)
On Oct 18, 2011, at 6:34 PM, Bijan Parsia wrote: (03)
> On 18 Oct 2011, at 23:52, Pat Hayes wrote:
>
> .....
> [snip]
>> Still, there has been widespread interest in extending the expressive power
>of a DL logic by adding some of the functionality of a rule language to it.
>This has the great appeal of keeping the DL fragment intact while allowing
>inference engines to step outside the DL world where needed,
>
> Er...why isn't this just "They are more expressive logics". (04)
Well, that is a very natural way to see it from a logically trained POV, I
agree. But the sense I often get is that this not in fact how implementers see
it, but more like using a rule engine to do quick patch-around hacks to
overcome a local lack of expressivity (eg doing a very quick check for
transitivity) but not even claiming any kind of completeness or attempting to
relate the rules to the logical semantics in other than a superficial way. I
dont accuse you or your colleagues of such sloppiness, of course, nor do I mean
to say that more careful or theoretically sound work is not done; but there are
certainly more, um, shall we say, scruffy points of view which just want to get
things working as quickly as possible. And my point in the email was only that
Ali might well have come across some discussion from within that more
engineering-oriented kind of tradition, is all. (05)
> I'm not sure I see, from the generic inference engine POV, the difference
>between, e.g., adding transitivity to ALC and adding DL Safe rules.
>(Obviously, from an implementation perspective, they are quite different. Some
>are sometimes amenable some of the time to hybrid proof procedures, but those
>aren't even always preferred these days, at least, in the sense of bolting
>together separatedly developed engines). (06)
Quite. I was talking about the bolting-together approach. (07)
Pat (08)
>
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