org.hypergraphdb.atom

Class HGRelTypeConstructor

java.lang.Object

org.hypergraphdb.atom.HGRelTypeConstructor

All Implemented Interfaces:

HGGraphHolder, HGSearchable<HGRelType,HGPersistentHandle>, HGAtomType, HGCompositeType

public class HGRelTypeConstructor
extends Object
implements HGSearchable<HGRelType,HGPersistentHandle>, HGCompositeType

The type of HGRelType. Even though we could have treated HGRelType, that would have created different RecordType which would have made it harder working purely with HGRelationships outside of Java (since one would have to get to the RecordType by querying on the class name). In any case, a HGRelType is conceptually not really a record...

Field Summary

Fields

Modifier and Type	Field and Description
static String	INDEX_NAME

Constructor Summary

Constructors

Constructor and Description
HGRelTypeConstructor()

Method Summary

Methods

Modifier and Type	Method and Description
HGSearchResult<HGPersistentHandle>	find(HGRelType key) Returns a HGSearchResult over all values matching a key in the searched entity.
Iterator<String>	getDimensionNames() Return an Iterator listing the names of all dimensions of this composite type.
HGProjection	getProjection(String dimensionName) Get the projection function for a particular dimension.
Object	make(HGPersistentHandle handle, LazyRef<HGHandle[]> targetSet, IncidenceSetRef incidenceSet) Construct a new run-time instance of a hypergraph atom.
void	release(HGPersistentHandle handle) Release a hypergraph value instance from the persistent store.
void	setHyperGraph(HyperGraph graph) During load time, set the HyperGraph instance to which this atom belongs.
HGPersistentHandle	store(Object instance) Store a run-time instance of a hypergraph atom into the hypergraph HGStore as a new atom.
boolean	subsumes(Object general, Object specific) A HGRelType X subsumes a HGRelType Y iff both have the same name and arity and each target atom of X subsumes the corresponding target atom of Y.

Methods inherited from class java.lang.Object

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

Field Detail

INDEX_NAME

public static final String INDEX_NAME

See Also:

Constant Field Values

Constructor Detail

HGRelTypeConstructor

public HGRelTypeConstructor()

Method Detail

make

public Object make(HGPersistentHandle handle,
          LazyRef<HGHandle[]> targetSet,
          IncidenceSetRef incidenceSet)

Description copied from interface: HGAtomType

Construct a new run-time instance of a hypergraph atom. A plain node must be constructed whenever the targetSet parameter is null or of length 0. Otherwise, a HGLink instance must be constructed.

It is not required that all atom types be able to construct both plain (node) atoms and HGLinks. It is up to an HGAtomType implementation to support either or both. When a HGLink counterpart is not available for a particular run-time type, an implementation may choose to create an instance of the default link value holder implementation HGValuedLink, provided by HyperGraph.

Specified by:

make in interface HGAtomType

Parameters:

handle - The HGPersistentHandle of the atom value.

targetSet - When the atom is a link, this parameter holds the target set of the link. When the atom is a node, the parameter is an array of 0 length.

incidenceSet - A lazy reference to the set of links pointing to this atom. This is null if we are constructing an internal/nested value of some complex type.

Returns:

The run-time atom instance. The return value should never be null. In case the handle points to an invalid instance (inexisting or with a erronous layout), the method should throw a HGException.

store

public HGPersistentHandle store(Object instance)

Description copied from interface: HGAtomType

Store a run-time instance of a hypergraph atom into the hypergraph HGStore as a new atom.

Specified by:

store in interface HGAtomType

Parameters:

instance - The atom instance.

Returns:

The persistent handle of the stored value.

release

public void release(HGPersistentHandle handle)

Description copied from interface: HGAtomType

Release a hypergraph value instance from the persistent store.

This method should be called when a HGPersistentHandle returned from the store is no longer in use.

Specified by:

release in interface HGAtomType

Parameters:

handle - The persistent handle of the value to release.

subsumes

public boolean subsumes(Object general,
               Object specific)

A HGRelType X subsumes a HGRelType Y iff both have the same name and arity and each target atom of X subsumes the corresponding target atom of Y.

In plain language this reflects the logical requirement that each instance relationship with type Y be also an instance (logically) of X.

Specified by:

subsumes in interface HGAtomType

Parameters:

general - The object which might be more general. Cannot be null.

specific - The object which might be more specific. Cannot be null.

Returns:

true if specific can be used whenever general is required and false otherwise.

find

public HGSearchResult<HGPersistentHandle> find(HGRelType key)

Description copied from interface: HGSearchable

Returns a HGSearchResult over all values matching a key in the searched entity.

If there are no matches, the method should return HGSearchResult.EMPTY. The method will never return a null. A HGException may be thrown in exceptional situations.

Specified by:

find in interface HGSearchable<HGRelType,HGPersistentHandle>

getDimensionNames

public Iterator<String> getDimensionNames()

Description copied from interface: HGCompositeType

Return an Iterator listing the names of all dimensions of this composite type. A projection function can be obtained through the getProjection method.

Specified by:

getDimensionNames in interface HGCompositeType

getProjection

public HGProjection getProjection(String dimensionName)

Description copied from interface: HGCompositeType

Get the projection function for a particular dimension.

Specified by:

getProjection in interface HGCompositeType

Parameters:

dimensionName - The name of the dimension.

Returns:

The HGProjection instance.

setHyperGraph

public void setHyperGraph(HyperGraph graph)

Description copied from interface: HGGraphHolder

During load time, set the HyperGraph instance to which this atom belongs.

Specified by:

setHyperGraph in interface HGGraphHolder