Re: draft response for LC comment 50

I used "standardized" as that is the wording in the RDF semantics
document, where the procedure is defined.  I think that the opaqueness
of the term is of benefit, as the allusion to naming appears to be part
of what was causing the problem.

peter


From: Ian Horrocks <ian.horrocks@comlab.ox.ac.uk>
Subject: Re: draft response for LC comment 50
Date: Tue, 17 Feb 2009 10:13:05 +0000

> Looks good -- thanks.
> 
> Minor comment: you change "named apart" to "standardised apart". This
> may be better, but is still relatively opaque. I wonder if anyone can
> think of anything better? I'm not to worried about this though because
> there is a clear explanation of what it means that is pointed to
> whenever it is used.
> 
> Ian
> 
> 
> 
> 
> On 14 Feb 2009, at 04:32, Peter F. Patel-Schneider wrote:
> 
>>
>> [Response for LC Comment 50:]
>>
>> 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 ..................................
>>
>>
>> The Direct Semantics document includes renaming of anonymous
>> individuals, and has been appropriately edited.
>> The diffs can be found at .......................
>>
>>
>> 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 Tuesday, 17 February 2009 12:08:25 UTC