Re: [LC Response] To Jonathan Rees Re: Problems with sameness and namedness of individuals

Thank you for your response to this comment.
While the changes you have made are not all to my taste (e.g. an  
anonymous thing that has a name remains an oxymoron, even if the name  
is only local), they address my concerns and I think will help keep  
newcomers on the right track. So I will say that I am satisfied with  
the working group's response to my comment.

Best
Jonathan

On Feb 19, 2009, at 11:04 AM, Peter F. Patel-Schneider wrote:

> Dear Jonathan,
>
> Thank you for your message
>  http://lists.w3.org/Archives/Public/public-owl-comments/2009Jan/0052.html
> on the OWL 2 Web Ontology Language last call drafts.
>
> It is quite often common to be a bit sloppy about the distinction
> between names and whatever they denote or mean, consider, for example,
> the common use of "the variable x" instead of "the variable named x".
> Often the loss in precision is gained back in readability.  In the
> interests of gaining this readability, the OWL Functional Syntax
> generally does not use markers in its syntactic categories to  
> indicate,
> for example, "ClassName" or "ClassID", instead using just "Class".
>
> Of necessity, this breaks down for individuals.  The overall syntactic
> category in the OWL Functional Syntax is "Individual", which is then
> divided into "NamedIndividual" and "AnonymousIndividual".  The
> alternative "IndividualName" and "IndividualAnonymousMarker" would  
> have
> been a reasonable alternative, but would have somewhat conflicted with
> the usage for other syntactic categories.
>
> As you point out, there are some parts of the document that should be
> revised so as to not be so confusing.
>
> The WG has decided to make the following modifications in response to
> your comments:
>
>
> Section 3.4:
>
> 	The axiom closure of an ontology O is the smallest set that
> 	contains all the axioms from each ontology O' in the import
> 	closure of O with all anonymous individuals *standardized* apart —  
> that
> 	is, the anonymous individuals from different ontologies in the
> 	import closure of O are treated as being different; see Section
> 	5.6.2 for further details.
>
> Section 5.6:
>
> 	Individuals *in the OWL 2 syntax* represent actual objects
> 	*(semantic individuals)* from the domain being modeled. There
> 	are two types of individuals in *the syntax of* OWL 2. Named
> 	individuals are given an explicit name that can be used in any
> 	ontology ** to refer to the same *semantic*
> 	individual. Anonymous individuals *do not have this global name
> 	and thus* are local to the ontology they are contained in.
>
> Section 5.6.2:
>
> 	Special treatment is required in case anonymous individuals with
> 	the same node ID occur in two different ontologies. In
> 	particular, these two individuals are structurally equivalent
> 	(because they have the same node ID); however, they are *not* treated
> 	as *identical* in the semantics of OWL 2 (because
> 	anonymous individuals are local to an ontology they are used
> 	in). The latter is achieved by *standardizing* anonymous individuals
> 	apart when constructing the axiom closure of an ontology O: if
> 	anonymous individuals with the same node ID occur in two
> 	different ontologies in the import closure of O, then one of
> 	these individuals MUST be replaced in the axiom closure of O
> 	with a fresh anonymous individual (i.e., with an anonymous
> 	individual having a globally unique node ID).
>
> Section 5.6.2 Example 2:
>
> 	In order to ensure that these individuals are treated
> 	differently by the semantics they are *standardized* apart when
> 	computing the axiom closure of O1 — either _:a5 in O1 is
> 	replaced with a fresh anonymous individual, or this is done for
> 	_:a5 in O2.
>
> Section 9.5:
>
> 	OWL 2 supports a rich set of axioms for stating assertions —
> 	axioms about individuals that are often also called facts. For
> 	clarity, different types of assertions are shown in three
> 	separate figures, Figure 18, 19, and 20. The SameIndividual
> 	assertion allows one to state that several individuals are all
> 	equal to each other *(more precisely, the several different
> 	individuals in the syntax denote the same semantic individual)*,
> 	while the DifferentIndividuals assertion allows for the opposite
> 	— that is, to state that several individuals are all different
> 	from each other. *(More precisely, that the several different
> 	individuals in the syntax are also semantically different.)* The
> 	ClassAssertion axiom allows one to state that an individual is
> 	an instance of a particular class.
>
> Section 11:
>
> 	The axiom closure Ax (with anonymous individuals *standardized* apart
> 	as explained in Section 5.6.2) of each OWL 2 ontology O MUST
> 	satisfy the global restrictions defined in this section. As
> 	explained in the literature [SROIQ], this restriction is
> 	necessary in order to obtain a decidable language. The formal
> 	definition of these conditions is rather technical, so it is
> 	split into two parts. Section 11.1 first introduces the notions
> 	of a property hierarchy and of simple object property
> 	expressions. These notions are then used in Section 11.2 to
> 	define the actual conditions on Ax.
>
>
> The diffs can be found at
> http://www.w3.org/2007/OWL/wiki/index.php?title=Syntax&diff=18157&oldid=18096
>
>
> The Direct Semantics document mentions standardizing of anonymous
> individuals, and has been appropriately edited.
> The diffs can be found at
> http://www.w3.org/2007/OWL/wiki/index.php?title=Direct_Semantics&diff=18158&oldid=17932
>
> The WG considers these to be editorial changes.
>
> Please acknowledge receipt of this email to
> <mailto:public-owl-comments@w3.org> (replying to this email should
> suffice). In your acknowledgment please let us know whether or not you
> are satisfied with the working group's response to your comment.
>
> Regards,
> Peter F. Patel-Schneider
> on behalf of the W3C OWL Working Group

Received on Thursday, 19 February 2009 22:24:00 UTC