W3C home > Mailing lists > Public > public-owl-wg@w3.org > February 2009

Re: draft response for LC comment 50

From: Ian Horrocks <ian.horrocks@comlab.ox.ac.uk>
Date: Tue, 17 Feb 2009 10:13:05 +0000
Message-Id: <B2E1195D-37DC-496B-8FD1-8DDC15BDFCE3@comlab.ox.ac.uk>
Cc: public-owl-wg@w3.org
To: Peter F. Patel-Schneider <pfps@research.bell-labs.com>
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.


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 10:13:48 UTC

This archive was generated by hypermail 2.3.1 : Tuesday, 6 January 2015 21:42:09 UTC