de.fuberlin.wiwiss.semmf.engine
Class MatchingEngine

java.lang.Object
  de.fuberlin.wiwiss.semmf.engine.MatchingEngine

public class MatchingEngine
extends java.lang.Object

Given a MatchingDescription this class performs semantic matching between a query graph and a set of resource graphs.

Version:

1.3 last modified 29.11.2006

Author:

Radoslaw Oldakowski

Nested Class Summary

private class	MatchingEngine.QueryCluster
private class	MatchingEngine.QueryGraph
private class	MatchingEngine.QueryNode A certain Node matching a particular pathExpr from a NodeMatchingDescription NOTE: There might be multiple QueryNodes matching the same pathExpr
private class	MatchingEngine.QueryProperty

Field Summary

private GraphMatchingDescription	gmd A MatchingDescription object containing all matching information based on which the engine performs the matching of a query graph against a set of resource graphs.
private MatchingEngine.QueryGraph	queryGraph This object stores all information from the query graph needed while matching against each resource graph.
private com.hp.hpl.jena.rdf.model.Model	queryModel Reference to the Jena Model holding the query graph
private com.hp.hpl.jena.rdf.model.Model	resModel Reference to the Jena Model holding all resource graphs

Constructor Summary

private	MatchingEngine(GraphMatchingDescription gmd) Constructor.
	MatchingEngine(java.lang.String mdURL) Constructor
	MatchingEngine(java.lang.String mdURL, java.lang.String lang) Constructor

Method Summary

MatchingResult	exec() Executes the matching.
private java.util.List	findNodes(com.hp.hpl.jena.rdf.model.Model m, java.lang.String pathExpr) This method searches inside the Model m for RDFNodes matching the given RDQL path expression.
private java.util.List	findQueryNodes(java.lang.String pathExpr) Searches inside a query model for RDFNodes matching the given path expression
private java.util.List	findResGraphEntries(java.lang.String pathExpr)
private java.util.List	findResNodes(java.lang.String pathExpr, java.lang.String resGraphEntryURI) Searches inside a resource model for RDFNodes matching the given pathexpression
private java.lang.String	generateRDQLstring(java.lang.String pathExpr) Given a path expression this method generates a full RDQL query string.
private com.hp.hpl.jena.rdf.model.RDFNode	getPropertyValue(com.hp.hpl.jena.rdf.model.Model m, com.hp.hpl.jena.rdf.model.Resource r, java.lang.String propURI) This method is used to retrieve the value of a property of a given node (RDF resource).
private MatchingEngine.QueryGraph	loadQueryGraph(GraphMatchingDescription gmd) This method loads all values from the query graph into memory and stores them using instances of the helper classes.
private void	recalcClusterResult(ClusterMatchingResultImpl cmr, float weight) If a certain node has to be matched in a reversed manner and it so happens that not every resource graph contains this particular node than the weight of this node inside this cluster has to be redistributed over the remaining nodes with respect to their relative weights.
private static java.lang.String	replaceAll(java.lang.String s, java.lang.String token, java.lang.String replacement) Replaces all occurances of a substring (token) inside an inputString
private java.lang.String	replaceGraphEntryPlaceholder(java.lang.String pathExpr, java.lang.String graphEntryURI) The general path expressions for resource nodes from a matching description contain a placeholder for the graph entry, which is replaced by this method with a particular graph entry URI

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

queryModel

private com.hp.hpl.jena.rdf.model.Model queryModel

Reference to the Jena Model holding the query graph

resModel

private com.hp.hpl.jena.rdf.model.Model resModel

Reference to the Jena Model holding all resource graphs

gmd

private GraphMatchingDescription gmd

A MatchingDescription object containing all matching information based on which the engine performs the matching of a query graph against a set of resource graphs.

queryGraph

private MatchingEngine.QueryGraph queryGraph

This object stores all information from the query graph needed while matching against each resource graph.

Constructor Detail

MatchingEngine

public MatchingEngine(java.lang.String mdURL)

Constructor

Parameters:

mdURL - location of the matching description in RDF/XML format

MatchingEngine

public MatchingEngine(java.lang.String mdURL,
                      java.lang.String lang)

Constructor

Parameters:

mdURL - location of the matching description

lang - serialization format of the matching description. Allowed values "RDF/XML", "N3", "N-TRIPLE".

MatchingEngine

private MatchingEngine(GraphMatchingDescription gmd)

Constructor.

Parameters:

gmd - object representing a matching description

Method Detail

exec

public MatchingResult exec()

Executes the matching.

Returns:

MatchingResult object

loadQueryGraph

private MatchingEngine.QueryGraph loadQueryGraph(GraphMatchingDescription gmd)

This method loads all values from the query graph into memory and stores them using instances of the helper classes.

Parameters:

gmd - GraphMatchingDescription

Returns:

an instance of the helper class QueryGraph

findResGraphEntries

private java.util.List findResGraphEntries(java.lang.String pathExpr)

Parameters:

pathExpr - path expression

Returns:

a List of RDFNodes which represent entries to resource graphs to be matched

findQueryNodes

private java.util.List findQueryNodes(java.lang.String pathExpr)

Searches inside a query model for RDFNodes matching the given path expression

Parameters:

pathExpr - RDQL path expression

Returns:

a List of RDFNodes

findResNodes

private java.util.List findResNodes(java.lang.String pathExpr,
                                    java.lang.String resGraphEntryURI)

Searches inside a resource model for RDFNodes matching the given pathexpression

Parameters:

pathExpr - RDQL path expression

resGraphEntryURI - URI of the entry node of a particular resource graph *

Returns:

a List of RDFNodes

findNodes

private java.util.List findNodes(com.hp.hpl.jena.rdf.model.Model m,
                                 java.lang.String pathExpr)

This method searches inside the Model m for RDFNodes matching the given RDQL path expression.

Parameters:

m - RDFModel on which the RDQL query is performed

pathExpr - RDQL path expression

Returns:

a List of all RDFNodes from Model m matching the given path expression

getPropertyValue

private com.hp.hpl.jena.rdf.model.RDFNode getPropertyValue(com.hp.hpl.jena.rdf.model.Model m,
                                                           com.hp.hpl.jena.rdf.model.Resource r,
                                                           java.lang.String propURI)

This method is used to retrieve the value of a property of a given node (RDF resource). NOTE: At this time only single property values are supported !!!!

Parameters:

m - Jena model in which the resource occurs

r - Jena Resource object

propURI - URI of the property

Returns:

Property value as an RDFNode object.

generateRDQLstring

private java.lang.String generateRDQLstring(java.lang.String pathExpr)

Given a path expression this method generates a full RDQL query string. NOTE: Because the path expression contains only full URI's the final query string does not contain any namespace declaration.

Parameters:

pathExpr - path expression

Returns:

a valid RDQL query string

replaceGraphEntryPlaceholder

private java.lang.String replaceGraphEntryPlaceholder(java.lang.String pathExpr,
                                                      java.lang.String graphEntryURI)

The general path expressions for resource nodes from a matching description contain a placeholder for the graph entry, which is replaced by this method with a particular graph entry URI

Parameters:

pathExpr - path expression

graphEntryURI - URI of the node which is the entry of the resource graph

Returns:

path expression for a particular resource graph

recalcClusterResult

private void recalcClusterResult(ClusterMatchingResultImpl cmr,
                                 float weight)

If a certain node has to be matched in a reversed manner and it so happens that not every resource graph contains this particular node than the weight of this node inside this cluster has to be redistributed over the remaining nodes with respect to their relative weights. This method redistributes the accumulated weight of all non existing nodes and recalculates the cluster similarity given the new node weights.

Parameters:

cmr - ClusterMatchingResult to be recalculated

weight - accumulated weight to be redistrubuted

replaceAll

private static java.lang.String replaceAll(java.lang.String s,
                                           java.lang.String token,
                                           java.lang.String replacement)

Replaces all occurances of a substring (token) inside an inputString

Parameters:

s - original string

token - String token to be replaced

replacement - String to replace the given token

Returns:

original string with the token replaced