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Re: comment on the fragment document: (inverse) functional and DL-Lite

From: Ivan Herman <ivan@w3.org>
Date: Thu, 06 Mar 2008 13:33:16 +0100
Message-ID: <47CFE48C.3070508@w3.org>
To: Boris Motik <boris.motik@comlab.ox.ac.uk>
CC: public-owl-wg@w3.org
Boris,

yep, our mails crossed, I just realized where I got it wrong in:

http://www.w3.org/mid/47CFDB45.20902@w3.org

so this issue is solved:-)

I guess what this revealed, however, and besides my own stupidity, is 
that it is still fairly difficult to read the document as is. Do not 
take me wrong: all my attempts and comments are just to try to find some 
ways of improving it...

Though your approach is clearly more concise, it makes it fairly 
difficult for a casual reader to have a clear picture of what is and 
what is not allowed in each fragment. This is made even more complicated 
by the fact that, I believe, many readers of this document may come in 
without trying to understand the full OWL 1.1 (after all, they try to 
find the minimum they can use!) and, as it stands now, they do have to 
have a thorough understanding of the full functional syntax before even 
having a hope to understand what these fragments are. This may be a lot 
to ask for, eg, RDF(S) users who try to find a minimal way to make use 
of better reasoners. (Although it may well be that an overview in this 
direction should be in another document and not this one. I am not sure.)

In any case, I think a table listing the features (in RDF) and adding 
marks on what can and cannot be used (or under what circumstances) would 
be great. Also, adding examples, like Bijan just did for the functional 
syntax, would be *very* helpful.

It would also be good to have some clear 'elevator pitch' for each of 
the fragments, probably in the introduction. Something which say "if 
your application/ontology is roughly like that, try to check whether 
this and this fragment works for you, and this will make you happy":-)

While I am at it, two more, purely editorial comments, if I may:

- I wonder whether the first table in 4.3.1. did not use the wrong 
typesetting. Ie, on the right hand coloumn the header cell should simply 
say 'then' and the rest belongs to the table below

- there is an overlap between the Tables in 4.3.2 and the RDFS 
entailement rules in

http://www.w3.org/TR/rdf-mt/#RDFSRules

I think it would be important to clarify how those two rule sets relate 
to one another. I would expect (but I may be wrong) that the rule set in 
this document is real superset of the RDFS rules although maybe some of 
the datatype-related rule sets are not in this one. (Also, formally, the 
RDFS entailement rules are informative, not normative...).

Actually, to make the relationship easier to swallow, I wonder whether 
it would not be better to follow the editorial style of the RDFS rule 
tables. It is only typesetting but, again, it may help the reader who 
moves from one document to the other. Just a thought...

Thanks!

Ivan



Boris Motik wrote:
> Hello Ivan,
> 
> Please let me explain the way in which the fragments have been defined. In the introduction, we said that, for each fragment, we
> show the productions that are different from the complete OWL 1.1 language. We did this in order to avoid duplication of the
> material.
> 
> Please note that the complete OWL 1.1 language contains the following production. Effectively, <objectPropertyAxiom> is responsible
> for OWL 1.1 allowing for (inverse)functional object properties.
> 
> objectPropertyAxiom :=
>     subObjectPropertyOf | equivalentObjectProperties |
>     disjointObjectProperties | inverseObjectProperties |
>     objectPropertyDomain | objectPropertyRange |
>     functionalObjectProperty | inverseFunctionalObjectProperty |
>     reflexiveObjectProperty | irreflexiveObjectProperty |
>     symetricObjectProperty | asymetricObjectProperty |
>     transitiveObjectProperty
> 
> 
> 
> In the DL-lite section, however, we redefined this production to the following one:
> 
> objectPropertyAxiom :=
>     subObjectPropertyOf | equivalentObjectProperties |
>     disjointObjectProperties | inverseObjectProperties |
>     objectPropertyDomain | objectPropertyRange |
>     symetricObjectProperty
> 
> Effectively, this disallows the (inverse)functional object properties in DL-lite. In other words, starting from the <ontology>
> nonterminal, there is now no way to get into the <functionalObjectProperty> nonterminal; hence, these are not allowed. The
> production <functionalObjectProperty> can thus be seen as "dangling".
> 
> 
> 
> We used this approach throughout the document: whenever some production is not redefined, we do not repeat it. Admittedly, while
> this makes the definition of each fragment more concise, it makes it also rather difficult to see what exactly is and what isn't
> supported by the fragment. But for this purpose, we presented an overview of the supported features before giving the grammar
> productions. We listed the supported and the not supported features.
> 
> 
> Now you are right in that we forgot to list the (inverse)functional object properties in the list of the missing features of
> DL-lite. Thanks for that; I've updated the document. If you find further omissions, please let us know and I'll add them to the
> appropriate section.
> 
> Regards,
> 
> 	Boris
> 
>> -----Original Message-----
>> From: public-owl-wg-request@w3.org [mailto:public-owl-wg-request@w3.org] On Behalf Of Ivan Herman
>> Sent: 06 March 2008 11:04
>> To: boris.motik@comlab.ox.ac.uk; bcg@cs.man.ac.uk
>> Cc: public-owl-wg@w3.org
>> Subject: comment on the fragment document: (inverse) functional and DL-Lite
>>
>> Boris, Bernardo,
>>
>> I went through
>>
>> http://www.w3.org/2007/OWL/wiki/Fragments_Proposal
>>
>> again today. One thing that I may have missed: I tried to see if I can
>> use (inverse)functional properties for DL-Lite or not. I did not find
>> any reference to those neither in 3.1 nor in 3.2. Again, I may have
>> missed something...
>>
>> I also have some more editorial comments, but I will send them in a
>> separate mail
>>
>> Ivan
>>
>> --
>>
>> Ivan Herman, W3C Semantic Web Activity Lead
>> Home: http://www.w3.org/People/Ivan/
>> PGP Key: http://www.ivan-herman.net/pgpkey.html
>> FOAF: http://www.ivan-herman.net/foaf.rdf
> 
> 

-- 

Ivan Herman, W3C Semantic Web Activity Lead
Home: http://www.w3.org/People/Ivan/
PGP Key: http://www.ivan-herman.net/pgpkey.html
FOAF: http://www.ivan-herman.net/foaf.rdf


Received on Thursday, 6 March 2008 12:33:27 GMT

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