- From: Peter F. Patel-Schneider <pfps@research.bell-labs.com>
- Date: Sun, 25 Nov 2007 05:32:58 -0500 (EST)
- To: jjc@hpl.hp.com
- Cc: public-owl-wg@w3.org
[See below for my take on how importing works in the various OWLs.] From: Jeremy Carroll <jjc@hpl.hp.com> Subject: owl:imports vs xinclude Date: Thu, 22 Nov 2007 14:29:10 +0000 [...] > Please can someone give a partisan and biased account of: > > a) what's wrong with owl:imports Nothing. :-) > and > > b) why xinclude fixes it XML inclusions provide similar power to the import-by-location view of imports that is in OWL Full, so use it instead of duplicating it. > (My gut feel is that this seems like unnecessary change, but since I > don't understand the motivations, I thought I should ask before a > knee-jerk disagreement!) [...] > Thanks > > Jeremy Importing ontologies in OWL DL [OWL S&AS 3.4]: [A]n owl:imports annotation also imports the contents of another OWL ontology into the current ontology. The imported ontology is the one, if any, that has as name the argument of the imports construct. (This treatment of imports is divorced from Web issues. The intended use of names for OWL ontologies is to make the name be the location of the ontology on the Web, but this is outside of this formal treatment.) Importing ontologies in OWL Full [OWL S&S 5.3]: Definition: Let K be a collection of RDF graphs. K is imports closed iff for every triple in any element of K of the form x owl:imports u . then K contains a graph that is the result of the RDF processing of the RDF/XML document, if any, accessible at u into an RDF graph. The imports closure of a collection of RDF graphs is the smallest import-closed collection of RDF graphs containing the graphs. Importing ontologies in OWL DL in the Web [OWL S&S 5.4]: Definition: Let T be the mapping from the abstract syntax to RDF graphs from Section 4.1. Let O be a collection of OWL DL ontologies and axioms and facts in abstract syntax form. O is said to be imports closed iff for any URI, u, in an imports directive in any ontology in O the RDF parsing of the document accessible on the Web at u results in T(K), where K is the ontology in O with name u. My summary of the OWL 1.0 situation: The situation for OWL DL is quite clear - the ontology retrievable at URI u is supposed to have name u. It is thus irrelevant whether imports is by location or by ontology name. For OWL Full, it is not required that the ontology at u have name u, but it is clear that imports is by location. The end result is that in OWL 1.0, imports works like entire-document XML inclusion. Importing ontologies in OWL 1.1 [SS&FS 3]: Each ontology contains a possibly empty set of import declarations. An ontology O directly imports an ontology O' if O contains an import declaration whose value is the ontology URI of O'. The relation imports is defined as a transitive closure of the relation directly imports. The axiom closure of an ontology O is the smallest set containing all the axioms of O and of all ontologies that O imports. Intuitively, an import declaration specification states that, when reasoning with an ontology O, one should consider not only the axioms of O, but the entire axiom closure of O. My summary of the OWL 1.1 situation: There is no treatment of importing in the OWL 1.1 Semantic document, which is a bit strange, so the controlling definition of importing in OWL 1.1 is in the SS&FS document. The definition is a bit unfinished, but the intent is clear that imports is by name, as in the OWL DL direct semantics, but without the intent that names and locations correspond. My take on imports vs XML inclusions is that XML includes is compatible with an imports-by-location mechanism, but that XML inclusions provide much more power. I do not believe that XML inclusions are appropriate for any non-XML OWL syntax, as they are too tied to XML. I do not completely know whether (full) XML inclusions would be appropriate for an XML-based OWL syntax, but it appears that they might be, provided that imports-by-location is the imports paradigm that is wanted. Peter F. Patel-Schneider Bell Labs Research
Received on Sunday, 25 November 2007 10:50:43 UTC