RE: draft response for 52b / JR6b

Hi Peter!

>-----Original Message-----
>From: Peter F. Patel-Schneider [mailto:pfps@research.bell-labs.com]
>Sent: Monday, March 23, 2009 5:59 PM
>To: Michael Schneider
>Cc: ivan@w3.org; public-owl-wg@w3.org
>Subject: Re: draft response for 52b / JR6b
>
>I have slightly lengthened this response to provide more background.
>
>See http://www.w3.org/2007/OWL/wiki/LC_Responses/JR6b
>
>peter

[[
The direct semantics directly provides one meaning 
for the constructed in OWL 2 ontologies.
The RDF-based semantics directly provides a meaning for all RDF graphs. 
As all OWL 2 ontologies can be mapped into RDF graphs, 
the RDF-based semantics provides another semantics 
for all the constructs in OWL 2 ontologies.
]]

I'm happy with this: "RDF-Based Semantics provides meaning for all RDF
graphs."

The third sentence, while technically redundant, will certainly be
helpful to people.

Btw, there is a typo in the first sentence: "constructed".

[[
The phrase "OWL 2", by itself, is now uniformly used 
to refer to the entire language, regardless of syntax or semantics. 
]]

I'm not really sure what this means, in particular together with the 
term "regardless of syntax". How can one talk about a language
regardless of syntax? I probably miss something here.

[[
The phrase "OWL 2 Full", by itself, is now uniformly used as a shorthand to
refer to the treatment of RDF graphs (particularly those RDF graphs that use
OWL 2 constructs) under the RDF-based semantics and thus, as you say, is a
combination of both syntax and semantics. This use of "OWL 2 Full" is
consistent with the use of "OWL Full" in the WebOnt documents that define
the original version of OWL.
]]

Fine: "OWL 2 Full" = Syntax and Semantics.

[[
"OWL 2 DL ontologies" are then those OWL 2 ontologies that admit reasoning
using well-known DL techniques when interpreted using the Direct Semantics,
and that can be mapped to RDF graphs and back again without affecting their
meaning in the direct semantics. This use of "OWL 2 DL ontologies" is
consistent with the use of "OWL DL" in the WebOnt documents that define the
original version of OWL." Section 3 of the OWL 2 Structural Specification
provides a comprehensive and compact list of the extra conditions that are
required for an OWL 2 ontology to be an OWL 2 DL ontology.
]]

I'm perfectly ok with talking about (the set of) "OWL 2 DL ontologies"
whenever 
talking about the "syntax things". However, I don't believe that the
statement

  "OWL 2 DL ontologies is consistent with the use of 'OWL DL' in the 
  WebOnt documents." 

is true (unless this was just a typo).

Here are two sentences that I found in S&AS Section 2, which claims to 
be normative, and which is actually about the Abstract Syntax, so it's
comparable with the Structural Spec document:

[[
The abstract syntax is expressed both for this smaller language, 
called the OWL Lite abstract syntax here, 
and also for a fuller style of OWL, 
called the OWL DL abstract syntax here.
]]

[[
OWL Lite and OWL DL closely correspond to the description logics 
known as SHIF(D) and SHION(D)
]]

So there seemed to be a distinction between the "OWL XX abstract syntax"
on the one side, and "OWL XX" as something that can correspond to
some description logic. I am presuming here that SHOIN is not just 
only a particular syntax.

Another hint to "OWL XX" = Syntax&Semantics, 
preceding the first citation above:

[[
(Note, however, that both OWL DL and OWL Lite 
do not provide all of the feature of RDF Schema.)
]]

I think this refers to the semantic aspects of RDFS and OWL XX, 
that, for example, RDFS provides for metamodelling and OWL XX not.
I don't see how this statement could be true if meant
only for the syntactic aspects of RDFS and OWL XX.

Nevertheless, I'm happy with the OWL 2 Full parts. In the meanwhile, the
RDF-Based Semantics has changed to use the term "OWL 2 RDF-Based Semantics"
everywhere where only the semantics is meant. There are two places where the
old Full spec is cited, maybe this should also be changed (looks strange to
compare the "OWL 2 RDF-Based Semantics" spec with the "OWL Full" spec).
Also, I have replaced all the occurrences of "the OWL 2 Full universe" (was
a Non-LC comment by Jonathan Rees). Now, at least much of the potential of
confusion should have gone. There are still quite a lot terms such as "OWL 2
Full interpretation", but they mirror the naming scheme of the old spec. 

Michael

--
Dipl.-Inform. Michael Schneider
Research Scientist, Dept. Information Process Engineering (IPE)
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Email: michael.schneider@fzi.de
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