RE: Punning discussion

Bijan Parsia wrote:

>On 24 Jan 2008, at 10:48, Michael Schneider wrote:
>[snip]
>>> From: Alan Ruttenberg
>>> Sent: Tuesday, January 22, 2008 9:21 AM
>>
>>> 3) [...] How does punning effect OWL Full?
>>
>> Punning is a DL-only feature,
>
>This doesn't seem right. If you take the equality free fragment of  
>OWL Full, you cannot distinguish between punning and hilog semantics.
>RDF, the language, doesn't have equality, so it is compatible with  
>punning.

The aim is to provide an RDF compatible semantics, which has additional
semantics for all OWL-1.1 language features. And the WG charter wants
OWL-1.1-Full to maintain backwards compatibility with OWL-1.0-Full.

In order to achieve this, my idea is to extend the existing set of
OWL-1.0-Full semantic conditions by additional semantic conditions, which
provide semantics for all the new RDF graphs as given on the left hand side
of the RDF-2-FS mapping table. There will also be text in a 1.1-Full draft
which is analogue to sections 5.1 and 5.3 in the AS&S. And, there will have
to be testcases analogue to the old testcases. Perhaps, a few corrections or
adaptations will be necessary wrt the old spec, but I don't expect to see a
major revison. 

This all is a task which should be doable in reasonable time, I believe. I
wonder how much time it took to create the old 1.0-Full spec? After all, the
old spec is not a large document, and building on top of it will make things
easier.

And to answer your statement above: There is, of course, an 'owl:sameAs'
construct both in the 1.1-RDF mapping, as in the 1.0-Full spec, and it has a
semantics in the latter. So I don't see how talking about "the equality free
fragment of OWL-Full" does help us in this discussion.

>> and cannot affect the definition of Full, as
>> long as Full is understood to be an RDF compatible language.
>
>The semantics specs something in a style that is *suggestive* of how  
>to extend it to OWL, but that's a different thing. It doesn't say  
>*how* to extend the semantics. It seems as legitimate to add  
>parameterized extension relations as anything else.

There is precedence given by the OWL-1.0-Full spec. And the WG charter wants
us to maintain backwards compatibility. This restricts the number of
possible solutions significantly. Of all remaining possible solutions, I
prefer the most straightforward and least time consuming one, which is IMO
the one I sketched above. 

But in the end, the WG has to decide how to forward in the OWL-Full
question. At least, from your long mail I can see that there might be
raising interest in such a discussion. :-)

>> In RDF, two
>> occurrences of the same name denote the same entity.
>
>Again, you seem to be inflating the style of the spec into a general  
>principle. It's very straightfoward to give a semantics where this is  
>not true but is equivalent to the RDF semantics.

AFAICS, the only place in the WDs where punning is mentioned is in chap. 2
of the semantics WD. There, essentially the only thing which is said about
punning is that the vocabulary is non-separated. However, there is also a
link to Boris' "metamodelling" paper. And in this paper, punning is defined
in sec. 3.2, definition 5. It's called "Contextual Semantics" there, but
later in the text, it is also called "punning" (last paragraph before
definition 6). This definition is what I refer to by saying "punning". 

>From the same paper I can see that it really seems to be possible to have
real metamodelling (definition 6), at least in SHOIQ(D), without falling
into undecidability. But I haven't read the details yet, so you or Boris or
anyone else may FIXME if I'm wrong. Nevertheless, it seems that it has not
been decided to use this "HiLog" semantics in 1.1-DL, for whatever reason,
but to use the weaker "contextual" (aka "punning") semantics instead.

If you now lift your hand and honestly tell me that OWL-1.1-DL allows this
so called "HiLog semantics", too (and, perhaps, that its left to the
implementors of OWL-1.1 reasoners to decide which of these semantics to
support), then I promise to sit myself down and carefully check the
technical details closely, and it may well be that I will never stand up
again and say a single evil word against "punning". :)

Cheers,
Michael