JavaScript is forgiving about matching the number of parameters in the function definition
with the number of parameters passed along from the calling statement. If you define a function with three parameters and the calling statement specifies only two, the third parameter variable value in that function is assigned a null value.
前面那个上网的问题是没有做镜像：
Controlling imports processing
To load an ontology without building the imports closure, call the method setProcessImports( false ) on the document manager object, or set the processImports property in the policy file. To be more selective, it is possible to ignore certain URI's when loading the imported documents. Call the method addIgnoreImport( String uri ) on the document manager object, or set the ignoreImport property in the policy.
A strength of working with ontologies is that we can reuse work done by other ontologists by importing their published ontologies. Often, however, this means that the ontology is only retrievable by traversing an Internet firewall. Even if this is possible, by using an HTTP proxy, it may impose unacceptable delay in loading an application. In the worst case, an ontology on which our application depends is temporarily or permanently unavailable from the original published URL. To assist with this common problem, the ontology document manager allows 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 duplicated on an internal mirror web site.
To specify this local redirection in the policy file, we use the following declarations:
<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" />
<language rdf:resource="http://www.w3.org/2000/01/rdf-schema" />
<prefix rdf:datatype="&xsd;string">rdfs</prefix>
</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. Any number of such re-directions may be specified in the policy file, or they can be added to the document manager object directly by calling the various 'add' methods (see the Javadoc for details). As a side-effect, this mechanism also means that ontologies can be named with any legal URI (not necessarily resolvable) - so long as the altURL is itself resolvable.
Specifying prefixes
A model keeps a table of URI prefixes that can be used to render URI's in the shortened prefix:name form, which is useful in displaying URI's in a readable way in user interfaces, and is essential in producing legal XML names that denote arbitrary URI's. The ontology model's table of prefixes can be initialized from a table kept by the document manager, which contains the standard prefixes plus any that are declared by in the policy file (or added to subsequently by method calls). To prevent the model's prefix table from being initialized in this way, use the property useDeclaredNsPrefixes in the policy file (with value 'false'), or call the method setUseDeclaredPrefixes on the ontology object.
Caching models
The final behaviour that the document manager provides to assist with loading ontology documents is a model cache. Suppose two ontologies, A and B both import ontology C. It would be nice not to have to read C twice when loading A and B. The document manager supports this use case by optionally caching C's model, indexed by C's URI. Then an attempt to import C from B, it previously having been loaded by A, would result in a significant time saving, and a reuse of the same model for C in both A and B.
To turn model caching on or off, use the policy property cacheModels, or call the method setCacheModels( boolean caching ). The default is caching on. The document manager's current model cache can be cleared at any time by calling clearCache().
Example
In the following example, we programmatically declare that the camera ontology is copied locally, and then load it using the public URL. Assume that the constant JENA has been initialized to the directory in which Jena is installed.
OntModel m = ModelFactory.createOntologyModel();
OntDocumentManager dm = m.getDocumentManager();
dm.addAltEntry( "http://www.xfront.com/owl/ontologies/camera/",
"file:" + JENA + "examples/data/camera.owl" );
m.read( "http://www.xfront.com/owl/ontologies/camera/" );
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2005/12/29 9:21:00
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为什么用jena api编的程序运行时需要连网？
