Animals本体：
<?xml version="1.0"?>
<rdf:RDF
xmlns="http://localhost/Animals.owl#"
xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
xmlns:xsd="http://www.w3.org/2001/XMLSchema#"
xmlns:rdfs="http://www.w3.org/2000/01/rdf-schema#"
xmlns:owl="http://www.w3.org/2002/07/owl#"
xml:base="http://localhost/Animals.owl">
<owl:Ontology rdf:about=""/>
<owl:Class rdf:about="#Animals">
<rdfs:label rdf:datatype="http://www.w3.org/2001/XMLSchema#string"
>动物</rdfs:label>
</owl:Class>
<owl:Class rdf:ID="Herbivores">
<rdfs:subClassOf>
<owl:Class rdf:ID="Animals"/>
</rdfs:subClassOf>
<rdfs:label rdf:datatype="http://www.w3.org/2001/XMLSchema#string"
>食草动物</rdfs:label>
</owl:Class>
<owl:Class rdf:ID="Predators">
<rdfs:subClassOf>
<owl:Class rdf:ID="Animals"/>
</rdfs:subClassOf>
<rdfs:label rdf:datatype="http://www.w3.org/2001/XMLSchema#string"
>食肉动物</rdfs:label>
</owl:Class>
<owl:DatatypeProperty rdf:ID="age">
<rdfs:label rdf:datatype="http://www.w3.org/2001/XMLSchema#string"
>年龄</rdfs:label>
<rdfs:domain rdf:resource="#Animals"/>
<rdfs:range rdf:resource="http://www.w3.org/2001/XMLSchema#int"/>
</owl:DatatypeProperty>
<owl:DatatypeProperty rdf:ID="weight">
<rdfs:label rdf:datatype="http://www.w3.org/2001/XMLSchema#string"
>重量</rdfs:label>
<rdfs:domain rdf:resource="#Animals"/>
<rdfs:range rdf:resource="http://www.w3.org/2001/XMLSchema#int"/>
</owl:DatatypeProperty>
<Predators rdf:ID="_00001">
<rdfs:label rdf:datatype="http://www.w3.org/2001/XMLSchema#string"
>狮子</rdfs:label>
<age rdf:datatype="http://www.w3.org/2001/XMLSchema#int"
>10</age>
<weight rdf:datatype="http://www.w3.org/2001/XMLSchema#int"
>500</weight>
</Predators>
</rdf:RDF>
converter类读取本体文件
public class Converter
{
protected OntModel m_model;
public Converter(String p_OWLFile)
{
load(p_OWLFile);
}
private void load(String p_OWLFile)
{
m_model = ModelFactory.createOntologyModel(OntModelSpec.OWL_MEM);
InputStream in = FileManager.get().open(p_OWLFile);
if(in == null)
{
throw new IllegalArgumentException("File: " + p_OWLFile + "not found!");
}
m_model.read(in, "");
}
}
OWLGraphConverter画图
public class OWLGraphConverter extends Converter
{
/**
* The created Prefuse graph.
*/
private Graph m_graph;
/**
* An ArrayList containing all the edges that have to be added to the Prefuse
* graph.
*/
private ArrayList<String[]> m_edges;
/**
* An Hashtable containing all the nodes in Prefuse graph.
*/
private Hashtable<String, Node> m_nodes;
/**
* An ArrayList containing the URI's of OWL classes that should not be converted
* into the Prefuse graph.
*/
private ArrayList<String> m_uselessType;
/**
* Creates a new instance of OWLGraphConverter
* @param p_OWLFile The path to the OWL file that needs to be converted.
* @param p_directed A boolean indicating whether the Prefuse graph needs to
* be directed.
*/
public OWLGraphConverter(String p_OWLFile, boolean p_directed)
{
super(p_OWLFile);
init(p_directed);
}
/**
* Initialize the graph converter.
* @param p_directed A boolean indicating whether the Prefuse graph needs to
* be directed.
*/
private void init(boolean p_directed)
{
m_edges = new ArrayList<String[]>();
m_nodes = new Hashtable<String, Node>();
// Create an ArrayList which contains URI's of nodes we do not want to
// visualize, because they are to general.
m_uselessType = new ArrayList<String>();
m_uselessType.add("http://www.w3.org/2002/07/owl#Class");
m_uselessType.add("http://www.w3.org/2000/01/rdf-schema#Class");
// Create the graph.
createGraph(p_directed);
}
/**
* Return the created Prefuse graph.
* @return The created Prefuse graph.
*/
public Graph getGraph()
{
return m_graph;
}
/**
* Create the Prefuse graph. This method creates an empty graph and adds the
* appropriate columns to the node- and edgestable. After that it gets the root
* class (owl:Thing) of the OWL graph and recursively starts building the graph
* from there.
* This method is automatically called from the constructors of this converter.
* @param p_directed A boolean indicating whether the Prefuse graph needs to
* be directed.
*/
private void createGraph(boolean p_directed)
{
// Create a new empty graph.
m_graph = new Graph(p_directed);
// Add the appropriate columns.
m_graph.getNodeTable().addColumn("URI", String.class);
m_graph.getNodeTable().addColumn("name", String.class);
m_graph.getNodeTable().addColumn("type", String.class);
m_graph.getEdgeTable().addColumn("label", String.class);
// Get the root node.
OntClass rootClass = m_model.getOntClass("http://localhost/Animals.owl#Animals");
// Build the entire tree.
buildGraph(rootClass);
// All the edges are stored in an ArrayList, because they can only be added
// if all the appropriate nodes exist. At this point this is the case, so
// all the nodes are created.
createEdges();
}
/**
* Build the Prefuse graph, this method is called recursively.
* @param p_currentClass The class which is being added to the graph.
*/
private void buildGraph(OntClass p_currentClass)
{
// If there is no root node yet, one is created.
Node currNode = m_graph.addNode();
currNode.setString("URI", p_currentClass.getURI());
currNode.setString("name", p_currentClass.getLocalName());
currNode.setString("type", "class");
// Walk trough the subclasses of the current class.
ExtendedIterator itClasses = p_currentClass.listSubClasses(true);
while(itClasses.hasNext())
{
//Recurse trough the subclasses of the current node.
buildGraph((OntClass) itClasses.next());
}
// Walk trough the instances of the current class.
ExtendedIterator itIndividuals = p_currentClass.listInstances();
while(itIndividuals.hasNext())
{
Individual foundIndividual = (Individual) itIndividuals.next();
if (foundIndividual.getURI() != null)
{
// Create the node for this instance.
Node node = m_graph.addNode();
node.setString("URI", foundIndividual.getURI());
node.setString("name", foundIndividual.getLocalName());
node.setString("type", "individual");
// Add this node to the nodes ArrayList.
m_nodes.put(foundIndividual.getURI(), node);
// Add the edges, connected to this node, to the edges ArrayList.
storeEdges(foundIndividual);
}
}
// Add this node to the nodes ArrayList.
m_nodes.put(p_currentClass.getURI(), currNode);
// Add the edges, connected to this node, to the edges ArrayList.
storeEdges(p_currentClass);
}
/**
* Temporarily store the edges which need to be added the graph. All the edges
* are stored in an ArrayList, because they can only be added if all the
* appropriate nodes exist. At this point this is the case, so all the nodes
* are created.
* @param p_resource The Jena OntResource of which the edges need to be stored.
*/
private void storeEdges(OntResource p_resource)
{
String sourceURI = p_resource.getURI();
if (!m_uselessType.contains(sourceURI))
{
StmtIterator itProperties = p_resource.listProperties();
while (itProperties.hasNext())
{
Statement property = itProperties.nextStatement();
String localName = property.getPredicate().getLocalName();
if (property.getObject().isResource())
{
String targetURI = ((Resource) property.getObject()).getURI();
if (!m_uselessType.contains(targetURI) && targetURI != null)
{
String[] edge = new String[3];
edge[0] = sourceURI;
edge[1] = localName;
edge[2] = targetURI;
m_edges.add(edge);
}
}
}
}
}
/**
* Create edges for the relevant properties of the resource.
*/
private void createEdges()
{
for (int i = 0; i < m_edges.size(); i++)
{
String[] strEdge = m_edges.get(i);
// Get the source and the target node.
Node source = m_nodes.get(strEdge[0]);
Node target = m_nodes.get(strEdge[2]);
Edge edge = m_graph.addEdge(source, target);
edge.setString("label", strEdge[1]);
}
}
}
最后由主程序调用
OWLGraphConverter类实际上就是一个递归运算，遍历本体的所有类和实例，而根目录就是：
OntClass rootClass = m_model.getOntClass("http://localhost/Animals.owl#Animals");
问题是我把这句改成：
Individual individual = m_model.getIndividual("http://localhost/Animals.owl#_00001");
删掉显示类的语句，只显示以_00001实例为根目录的所有属性，报空指针错：
Exception in thread "main" java.lang.NullPointerException
at owl2prefuse.graph.OWLGraphConverter.buildGraph(OWLGraphConverter.java:127)
at owl2prefuse.graph.OWLGraphConverter.createGraph(OWLGraphConverter.java:111)
at owl2prefuse.graph.OWLGraphConverter.init(OWLGraphConverter.java:76)
at owl2prefuse.graph.OWLGraphConverter.<init>(OWLGraphConverter.java:55)
at Demo.<init>(Demo.java:30)
at Demo.main(Demo.java:50)
不知道为什么，急啊，望各位高手不吝赐教啊！！！
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2009/6/15 9:24:00
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owl2prefuse如何遍历本体实例？
