com.bigdata.rdf.sail.webapp

Class VoID

java.lang.Object

com.bigdata.rdf.sail.webapp.VoID

public class VoID
extends Object

Helper class for VoID descriptions.

Author:

Bryan Thompson

See Also:

Describing Linked Datasets with the VoID Vocabulary

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
protected static class	VoID.IVCount An IV and a counter for that IV.

Constructor Summary

Constructors

Constructor and Description
VoID(org.openrdf.model.Graph g, AbstractTripleStore tripleStore, String[] serviceURI, org.openrdf.model.Resource aDataset)

Method Summary

Methods

Modifier and Type	Method and Description
protected static VoID.IVCount[]	classUsage(AbstractTripleStore kb) Return an efficient statistical summary for the class partitions.
protected static VoID.IVCount[]	classUsage(AbstractTripleStore kb, IV<?,?> civ, VoID.IVCount[] classPartitionCounts) Return the class partition statistics for the named graph.
void	describeDataSet(boolean describeStatistics, boolean describeNamedGraphs) Describe the default data set (the one identified by the namespace associated with the AbstractTripleStore.
protected void	describeGraph(org.openrdf.model.Resource graph, VoID.IVCount[] predicatePartitionCounts, VoID.IVCount[] classPartitionCounts) Describe a named or default graph.
protected void	describeVocabularies(VoID.IVCount[] predicatePartitionCounts) Describe the vocabularies which are in use in the KB based on the predicate partition statistics.
protected static VoID.IVCount[]	predicateUsage(AbstractTripleStore kb) Return an array of the distinct predicates in the KB ordered by their descending frequency of use.
protected static VoID.IVCount[]	predicateUsage(AbstractTripleStore kb, IV<?,?> civ, VoID.IVCount[] predicatePartitionCounts) Return the predicate partition statistics for the named graph.

Methods inherited from class java.lang.Object

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

Constructor Detail

VoID

public VoID(org.openrdf.model.Graph g,
    AbstractTripleStore tripleStore,
    String[] serviceURI,
    org.openrdf.model.Resource aDataset)

Parameters:

g - Where to assemble the description.

tripleStore - The KB instance to be described.

serviceURI - The SPARQL service end point.

aDefaultDataset - The data set identifier that will be used on the description (the bigdata namespace of the dataset is obtained from the tripleStore).

Method Detail

describeDataSet

public void describeDataSet(boolean describeStatistics,
                   boolean describeNamedGraphs)

Describe the default data set (the one identified by the namespace associated with the AbstractTripleStore.

Parameters:

describeStatistics - When true, the VoID description will include the VoidVocabularyDecl.vocabulary declarations, the property partition statistics, and the class partition statistics.

describeNamedGraphs - When true, each named graph will also be described in in the same level of detail as the default graph. Otherwise only the default graph will be described.

describeVocabularies

protected void describeVocabularies(VoID.IVCount[] predicatePartitionCounts)

Describe the vocabularies which are in use in the KB based on the predicate partition statistics.

Parameters:

predicateParitionCounts - The predicate partition statistics.

describeGraph

protected void describeGraph(org.openrdf.model.Resource graph,
                 VoID.IVCount[] predicatePartitionCounts,
                 VoID.IVCount[] classPartitionCounts)

Describe a named or default graph.

Parameters:

graph - The named graph.

predicatePartitionCounts - The predicate partition statistics for that graph.

classPartitionCounts - The class partition statistics for that graph.

predicateUsage

protected static VoID.IVCount[] predicateUsage(AbstractTripleStore kb)

Return an array of the distinct predicates in the KB ordered by their descending frequency of use. The IVs in the returned array will have been resolved to the corresponding BigdataURIs which can be accessed using IVCache.getValue().

Parameters:

kb - The KB instance.

predicateUsage

protected static VoID.IVCount[] predicateUsage(AbstractTripleStore kb,
                            IV<?,?> civ,
                            VoID.IVCount[] predicatePartitionCounts)

Return the predicate partition statistics for the named graph.

Parameters:

kb - The KB instance.

civ - The IV of a named graph (required).

Returns:

The predicate partition statistics for that named graph. Only predicate partitions which are non-empty are returned.

classUsage

protected static VoID.IVCount[] classUsage(AbstractTripleStore kb)

Return an efficient statistical summary for the class partitions. The SPARQL query for this is

 SELECT  ?class (COUNT(?s) AS ?count ) { ?s a ?class } GROUP BY ?class ORDER BY ?count
 

However, it is much efficient to scan POS for

 rdf:type ?o ?s
 

and report the range count of

 rdf:type ?o ?s
 

for each distinct value of ?o.

Parameters:

kb - The KB instance.

Returns:

The class usage statistics.

classUsage

protected static VoID.IVCount[] classUsage(AbstractTripleStore kb,
                        IV<?,?> civ,
                        VoID.IVCount[] classPartitionCounts)

Return the class partition statistics for the named graph.

Parameters:

kb - The KB instance.

civ - The IV of a named graph (required).

Returns:

The class partition statistics for that named graph. Only class partitions which are non-empty are returned.