http://jena.sourceforge.net/ontology/index.html
这里有详细介绍：
Managing file references
An advantage of working with ontologies is that we can reuse work done by other ontologists, by importing their published ontologies into our own. Sometimes, however, this means that there is an Internet firewall between the ontology-based application and the source of an imported ontology. Even if it's possible to traverse the firewall through an HTTP proxy, retrieving files from an HTTP connection may impose unacceptable delays when starting an application. In the worst case, we may find that ontology on which our application depends is temporarily or permanently unavailable from the original published URL. To alleviate these commonly experienced problems, you can use the ontology document manager to set up a a local indirection, so that an attempt to import a document from a given published URL means that a local copy of the document is retrieved instead. This may be a file copy, or simply a pointer to a local mirror web site.
To specify this local redirection in the policy file, use the following declarations:
<OntologySpec>
<publicURI rdf:resource="… the public URI to map from…" />
<altURL rdf:resource="… the local URL to map to …" />
<!-- optional ontology language term -->
<language rdf:resource="… encoding used …" />
<!-- optional prefix to associate with the public URL -->
<prefix rdf:datatype="&xsd;string">a prefix</prefix>
</OntologySpec>
For example:
<OntologySpec>
<!-- local version of the RDFS vocabulary -->
<publicURI rdf:resource="http://www.w3.org/2000/01/rdf-schema" />
<altURL rdf:resource="file:vocabularies/rdf-schema.rdf" />
</OntologySpec>
This specifies that an attempt to load the RDFS vocabulary from http://www.w3.org/2000/01/rdf-schema will transparently cause file:vocabularies/rdf-schema.rdf to be fetched instead. You can specify any number of such re-directions in the policy file, or you can add them to the document manager object directly by calling the various setter methods (see the Javadoc for details). As a side-effect, this mechanism also means that ontologies may be named with any legal URI (not necessarily resolvable) - so long as the altURL is itself resolvable.
Note that the OntDocumentManager is an application of Jena's File Manager. See the notes on FileManager for details of additional options.
In the following example, I programmatically declare that the ESWC ontology is replicated locally on disk, and then I load it using the public URL. Assume that the constant JENA has been initialised to the directory in which Jena was installed.
OntModel m = ModelFactory.createOntologyModel();
OntDocumentManager dm = m.getDocumentManager();
dm.addAltEntry( "http://www.eswc2006.org/technologies/ontology",
"file:" + JENA + "src-examples/data/eswc-2006-09-21.rdf" );
m.read( "http://www.eswc2006.org/technologies/ontology" );
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2009/4/7 19:39:00
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