Re: LC responses 28, 48 & 58

(cc-ing Sandro explicitly because this affects the intro document as well)

Sigh. This naming issue will haunt us until we retire...

On my way back home from the 'tute I tried to combine some sort of an
"ideal" (a.k.a. more mathematical) view of the various components and
their naming with the accepted practice as referred to by Jim and
Michael (and Frank, actually). Here is what I think we have

- We have OWL 2 (no suffix!). This is defined in the structural spec,
essentially via UML. It has a representation in RDF using the OWL 2
vocabulary. RDF graphs that 'behave' well v.a.v. data types (this is my
understanding from Boris) can be mapped to the UML. In other words,
modulo some misbehaving RDF graphs (that are rare in practice) the UML
structure and the RDF are equivalent.

- We have two possible semantics for OWL 2: Direct and RDF Based. Both
can be used with all RDF graphs.

- We also have syntactic subsets of OWL 2. These are the OWL DL
Syntactic Subset, and the OWL EL/QL/RL syntactic subsets. We can also
consider OWL 2 as a whole as a syntactic subset with empty restrictions.

- The combination of any subsets with any of the two semantics are
possible. However, only certain combinations have proven to be useful in
practice for different reasons. These are:

 - The whole of OWL 2 using the RDF Based Semantics; this is commonly
referred to as OWL 2 Full. Note that OWL 2 Full has the extra bonus of
providing semantics for those rare RDF graphs that cannot be mapped onto
the OWL 2 Structure
 - The OWL DL Syntactic Subset and the Direct Semantics, this is
commonly referred to as OWL 2 DL
 - The OWL EL and QL Syntactic Subsets and the Direct Semantics, these
are commonly referred to as OWL EL and OWL QL
 - The OWL RL Syntactic Subset and the RDF Based Semantics, this is
commonly referred to as OWL RL. Note that a separate theorem shows that,
in many important cases, the OWL RL Syntactic Subset can actually be
used with both Semantics and they behave in an identical manner, ie,
both combinations are meaningful.

In other words, we may want to strictly separate the notion of _OWL XX
Syntactic Subset_ and certain combination of these with particular
semantics.

Is this what Michael refers to? Can that be put into a better language
(maybe we will have to find a better name for OWL XX Syntactic Subset)

I am not sure it helps; it helped to clarify my thoughts on the bus...

Ivan

Michael Schneider wrote:
>> -----Original Message-----
>> From: Peter F. Patel-Schneider [mailto:pfps@research.bell-labs.com]
>> Sent: Wednesday, March 11, 2009 1:00 AM
>> To: Michael Schneider
>> Cc: public-owl-wg@w3.org
>> Subject: Re: LC responses 28, 48 & 58
> 
>>> [[
>>> OWL 2 separates syntax from semantics, and that OWL 2 Full,
>>> DL, QL, EL and RL are all refer to syntactic variants,
>>> ]]
>>>
>>> Frankly, this makes no sense to me. OWL 2 Full is certainly not a
>> "syntactic
>>> variant", just as OWL 1 Full hasn't been.
>> OWL 2 Full is all ontologies / all RDF graphs.  A syntactic variant.
> 
> If "OWL 2 Full" means the set of all RDF graphs, then the term 
> is redundant.
> 
> In this case, and if "OWL Full" was also intended to be used 
> in that way, then "OWL 2 Full" would be the same as "OWL Full" 
> (and any "OWL N Full" in the future). I cannot make much sense 
> of this.
> 
> If, however, "OWL Full" was /not/ meant to be understood in this
> way (and this is how I read the original spec), then I do not
> see any justification for changing this view in OWL 2. 
> 
>> This matches the wording in the last paragraph of Section 2.3 of the
>> Document Overview but not that earlier in the Section.  I have proposed
>> changes to the Document Overview in my next message.
>>
>>> In the OWL 1 Full spec, there existed semantic-related terms like "OWL
>> Full
>>> interpretation" and "OWL Full entails". And OWL Full was characterized
>> as
>>> follows in a semantic way:
>>>
>>> <http://www.w3.org/TR/owl-semantics/rdfs.html#5.3>
>>> [[
>>> OWL Full augments the common conditions with conditions
>>> that force the parts of the OWL universe
>>> to be the same as their analogues in RDF.
>>> [...]
>>> ]]
>>>
>> And, as Ian says, this story is being changed slightly.
> 
> I don't believe that Frank and the other commenters asked for such a change:
> 
> <http://lists.w3.org/Archives/Public/public-owl-comments/2009Jan/0035.html>
> [[
> Hence, we strongly insist that the names are adjusted to be in
> line with common practice.
> ]]
> 
> And from their comments it's hard for me to foresee that they will accept such a change to happen. I'm fearing that we are on a dangerous path here. Changes on /that/ level (e.g. the meaning of the basic names) will be relevant even to parties that generally aren't too interested in technical details, I guess.
> 
>>> "OWL 2 Full" exclusively to mean the /semantics/.
>> I argue against this.
> 
> And so do I. I want to see "OWL 2 Full" to mean the whole language, not 
> just a single component of it, i.e. neither only semantics, 
> nor only syntax. That's what I believe is "common practice".
> Of course, not only for "OWL Full", but for all the names.
> 
> But if you disagree, then there is an easy way to find out: 
> Just let's ask the public what they think the term "OWL DL" 
> refers to: Only the syntax, only the semantics, or the whole 
> language consisting of both syntax and semantics?
> 
> Or, as a start: Just let's ask Frank what he means by "common practice",
> because he wasn't particularly clear on this, IMHO. 
> 
>> I'm quite willing to abuse the notation and let OWL 2 Full mean
>> ontologies under the RDF-Based Semantics as well as just a syntax, just
>> as I would let OWL 2 DL mean ontologies that meet the syntactic
>> characterisation of OWL 2 DL under the Direct Semantics as well as just
>> a syntax.
> 
> That's certainly appropriate and common in practice. But if I am 
> being asked by confused people what I precisely mean by the term 
> "OWL 2 DL", only the syntax or the language as a whole, then there 
> is no doubt that I will answer that I mean the whole language 
> (syntax + semantics).
> 
> Just as I would answer for virtually every other language that I am 
> aware of. People may claim that they only mean the syntax when they 
> talk about C++. But the C++ ISO consortium will definitely tell them 
> that the whole language is meant, not just the syntax. And, I guess, 
> if a textbook does otherwise, it will receive a lot of feedback, or 
> eventually none at all... :)
>  
> And, in fact, the syntax and semantics of C++ do not have own names,
> they are only called something like "C++ syntax" and "C++ semantics". 
> Are there any other languages, which have special names for their 
> syntax and their semantics, as in OWL 2? Actually, in OWL 2 
> the situation is even more peculiar, since the concrete languages 
> in the OWL 2 family do not even have own names (officially)! We 
> currently have to talk about 
> 
>   "the language that has 
>    OWL 2 DL as its syntax 
>    and the OWL 2 Direct Semantics as its semantics"
> 
> Doesn't this bother anyone else then me?
> 
> FWIW, whatever our decision will be, I will, whenever I am talking to
> my colleagues or to FZI's technological partners or industrial customers, 
> ALWAYS call this whole language "OWL 2 DL", and the syntax will be the 
> "OWL 2 DL syntax", and the semantics will be the "OWL 2 DL semantics". 
> I would consider everything else to be confusing, to say the least.
>  
>> Note that part of the OWL 2 DL syntactic conditions have been chosen
>> only to allow for mapping into and out of RDF - these conditions are not
>> necessary to achieve the semantic and computational benefits of OWL 2
>> DL.
>>
>>> But Jonathan Rees had a comment on this:
>>>
>>> http://lists.w3.org/Archives/Public/public-owl-
>> comments/2009Jan/0068.html
>>> [[
>>> And are you sure that you want "OWL 2 Full" to be the name of a
>> semantics?
>>> That seems OK to me, but it's sort of weird.  In common use I think it
>>> will be taken to mean a language consisting of a combination of syntax
>>> (RDF in any of its serializations) and
>>> semantics (conditions on interpretation of the OWL 2 vocabulary).
>>> ]]
>>>
>>> This sounds reasonable to me, so I am strongly inclined to follow this
>>> comment. The term "OWL 2 Full" would then mean the whole language. But
>> not
>>> the syntax alone. This would make no sense to me, because the syntax
>> of OWL
>>> 2 Full is RDF, just as for OWL 1 Full and RDFS.
>> Well, I would argue that the true language of OWL 2 Full is the
>> Structural Specification. 
> 
> I'm afraid, I won't adopt this particular view.
> 
>> The RDF serialisation is just something that
>> fits better into the current preferred Semantic Web story.
>>
>>> Best,
>>> Michael
>> peter
> 
> Michael
> 
> --
> Dipl.-Inform. Michael Schneider
> Research Scientist, Dept. Information Process Engineering (IPE)
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-- 

Ivan Herman, W3C Semantic Web Activity Lead
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