- From: Jeff Heflin <heflin@cse.lehigh.edu>
- Date: Tue, 23 Apr 2002 15:28:22 -0400
- To: tim finin <finin@cs.umbc.edu>
- CC: www-rdf-logic@w3.org
Tim, If you refer to a term in an ontology without importing then I suggest that you are using a name without agreeing to its definition. This is not an error condition, but it may mean that DAML+OIL-compliant agents won't conclude everything you intend them to. Now, if the user community feels this is unreasonable, then we can consider having a default imports that corresponds to each use of a namespace for the upcoming WebOnt language, but I'm not sure that's the best way to go. I'd be interested in hearing opinions on this. In any case, I see that WebOnt needs to do a better job of describing imports and make more explicit statements about its effects. As for the diagram, sorry I should have shown how explicit imports links could help. Of course, the links currently shown are just property links. I see two ways where imports links could be used to achieve the desired effect: method 1: my-doc daml:imports orig-schema my-doc daml:imports good-schema method 2: my-doc daml:imports orig-schema orig-schema daml:imports good-schema Note, these methods assume no other imports statements for the relevant ontologies. For example, if orig-schema daml:imports bad-schema, then my-doc could not import orig-schema without accepting the definitions in bad-schema (since imports is transitive). Jeff tim finin wrote: > > Jeff Heflin wrote: > > ... Since I was the initial proponent of daml:imports on the Joint > > Committee, let me address this issue. You are absolutely correct that > > the imports statement must be used. Simply refering to a namespace does > > not include any ontology definitions. You must make the imports > > statement explicit. Period. ... > > So, what does it mean if one refers to a term in an ontology > without importing it? Should this be considered an error? If > so, is there a reasonable recovery technique, like ignoring > triples using externally defined terms not imported? > > > ... The problem with using RDF namespaces to decide which schemas are > > relevant is that multiple files may contain different definitions about > > the same URI. See the attached GIF for example. The URI for Dolphin has > > additional definitions in two schemas, good-schema and bad-schema. These > > definitions are simply rdfs:subClassOf statements that happen to have > > orig-schema#Dolphin as their subject. The problem with simply using > > namespaces is I can't say that my-doc agrees with the definitions of > > Dolphin found in good-schema but not those found in bad-schema. This is > > why daml:imports was an essential component of the language. ... > > Jeff -- I wonder if you can clarify the situation described by the gif > image. In the imports-required case, wouldn't it make sense only if > my-docs imported orig-schema which subsequently imported good-schema and > bad-schema? I always assumed that importing was transitive, since the model > was informally described as "like including the file". If so, then my-doc > can't use orig-schema without also committing to both good-schema and bad-schema. > > tim > > ------------------------------------------------------------------------ > [Image]
Received on Tuesday, 23 April 2002 15:28:45 UTC