Re: Review OWL 2 MT Semantics Document

Hi Boris,

On 8 Sep 2008, at 08:55, Boris Motik wrote:

>>>> * 2.1 Vocabulary
>>>> - Definition of N_{DT}: This is inconsistent with the OWL 2
>>>>  Specification: in Section 4
>>>>  [ ] , it says
>>>>  that N_DT *must not* contain rdfs:Literal.
>>> All sets in the definition of the vocabulary are now called V_*.
>>> Thus, we now have N_DT in the datatype map and V_DT in the
>>> vocabulary. I hope things are now clearer.
>> I think it's a good idea to change the N_* to V_*. However, now the
>> vocabulary V *over D* is not related to D any more: the enumeration  
>> of
>> the V_* should at least contain the statements V_{DT} = N_{DT},  
>> V_{LT}
>> = N_{LT}, and V_{FA} = N_{FA}, shouldn't it?
> That was already there; for example, the text said V_LT is the set  
> of all literals of D. Nevertheless, I added an explicit equality
> to make things clear.

Sorry for overlooking this and thanks for making the equality explicit.
>> Thanks, but I'm not 100% satisfied with the new heading "Keys":
>> Strictly speaking, "KeyFor(PE_1, ..., PE_n, CE)" is a key
>> *constraint*. A key is an n-tuple of individuals filling the
>> properties PE_1, ..., PE_n. Being picky, I'd rather like to see the
>> heading "Key Constraints" here ...
> I'd prefer avoiding the term "constraint", as it might be confused  
> with "integrity constraints". The difference between integrity
> constraints and axioms is something that is confusing OWL users  
> quite a bit in general. Furthermore, I'm not sure why this type of
> axioms should be called a constraint while other axioms should not:  
> all of them are just first-order sentences.

I'm not insisting on the term "constraint". I was just stumbling over  
the name "key" for this type of axiom. I'd be fine with "key  
statement" instead of "key constraint". But perhaps I'm getting bogged  
down in unimportant details here ... ;-)

>>>> [Semantics of key constraints]
>>> In private communication Peter has suggested an even shorter way of
>>> writing this condition.
>> Good, much clearer! I just feel that it should be made clearer that
>> the antecedent of the "imply" is everything behind the colon. I know
>> that this property doesn't make sense otherwise, but an extra pair of
>> brackets or so might help the reader to grasp the structure of this
>> non-trivial statement.
> I'd prefer not introducing brackets because this statement is meant  
> to be read as a natural-language statement. I appreciate your
> concerns, though, so I've reformatted and rephrased the condition a  
> bit to make your point clearer (I hope).

I see your point about the brackets. The new if-then format is clear.



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Received on Monday, 8 September 2008 19:58:12 UTC