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RDF Semantics: use of functions IEXT / ICEXT

From: <herman.ter.horst@philips.com>
Date: Fri, 21 Feb 2003 16:58:28 +0100
To: www-rdf-comments@w3.org, phayes@ai.uwf.edu
Message-ID: <OF4F674DBD.032CC3F9-ON41256CD4.00490A0B-C1256CD4.0057EAB8@diamond.philips.com>

RDF Semantics document,
last call version, 23 january 2003
These comments were mailed earlier to the WebOnt WG [1].

A consequence of the (new) setup of the RDF semantics
is that for each occurrence of IEXT(x) or ICEXT(x), it
should be clear that x is in the domain of the function
involved.  (For IEXT, this domain is the set IP. 
For ICEXT, the domain is the set IC; compare my
other comment on this to rdf-comments [2].)
For example, in Section 3.3 the semantic conditions on 
subClassOf and subPropertyOf take care of this explicitly.
It seems that this point is not taken care of completely
consistently throughout the document.

In Section 3.1, RDF interpretations,
in the table defining an rdf-interpretation, IEXT(I(rdf:type)) 
is used before it is clear that I(rdf:type) is in the 
domain of this function (i.e., the set IP).
Switching the first two lines of this table would remedy this.

Similarly, it seems appropriate to move the semantic 
conditions on IC and IP in Section 3.3:
> IC contains ...[many items]
> IP contains ...[many items]
to become the first conditions, as each of the other
conditions in this table actually uses one or more of these 
conditions.

The semantic conditions on rdfs:range and rdfs:domain in Section 3.3
do not yet incorporate explicit domain assumptions as just
discussed.  It seems that additions such as the following need 
therefore to be made:

If <x,y> is in IEXT(I(rdfs:range)) 
[then x is in IP and y is in IC] and 
[if, in addition,] <u,v> is in IEXT(x) then 
v is in ICEXT(y)

If <x,y> is in IEXT(I(rdfs:domain)) 
[then x is in IP and y is in IC] and 
[if, in addition,] <u,v> is in IEXT(x) then 
u is in ICEXT(y)

The last call versions of these statements (i.e., this text
without the [...]-additions) seem to be
remnants from the April 2002 version of the RDF MT, where
IEXT as well as ICEXT had all of IR as their domain.

Herman ter Horst
Philips Research

[1] http://lists.w3.org/Archives/Public/www-webont-wg/2003Feb/0067.html
[2] http://lists.w3.org/Archives/Public/www-rdf-comments/2003JanMar/0348.html
Received on Friday, 21 February 2003 11:01:46 GMT

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