org.hypergraphdb.type
Class AtomRefType

java.lang.Object
  org.hypergraphdb.type.AtomRefType

All Implemented Interfaces:

HGGraphHolder, HGSearchable<HGPersistentHandle,HGPersistentHandle>, ByteArrayConverter<java.lang.Object>, HGAtomType

public class AtomRefType
extends java.lang.Object
implements HGAtomType, HGSearchable<HGPersistentHandle,HGPersistentHandle>, ByteArrayConverter<java.lang.Object>

Represents the type of a HGAtomRef value. This type implementation handles the behavior of atom references depending on their mode (@see HGAtomRef.java for a thorough description of reference modes and the relationship of an atom reference to its referent).

The implementation maintains a count for all types of references and triggers the correct action (as the case may be) on the referent when all counts go to 0.

Author:

Borislav Iordanov

Field Summary

static HGPersistentHandle

HGHANDLE

Constructor Summary

AtomRefType()

Method Summary

HGSearchResult<HGPersistentHandle>	find(HGPersistentHandle key) The key is expected to be of type HGAtomRef OR of type HGHandle.
java.lang.Object	fromByteArray(byte[] byteArray)
java.lang.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 hg) During load time, set the HyperGraph instance to which this atom belongs.
HGPersistentHandle	store(java.lang.Object instance) Store a run-time instance of a hypergraph atom into the hypergraph HGStore as a new atom.
boolean	subsumes(java.lang.Object general, java.lang.Object specific) A generic semantic predicate that returns true if the first argument is more general than the second.
byte[]	toByteArray(java.lang.Object object)

Methods inherited from class java.lang.Object

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

Field Detail

HGHANDLE

public static final HGPersistentHandle HGHANDLE

Constructor Detail

AtomRefType

public AtomRefType()

Method Detail

setHyperGraph

public void setHyperGraph(HyperGraph hg)

Description copied from interface: HGGraphHolder

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

Specified by:

setHyperGraph in interface HGGraphHolder

make

public java.lang.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 - TODO

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(java.lang.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(java.lang.Object general,
                        java.lang.Object specific)

Description copied from interface: HGAtomType

A generic semantic predicate that returns true if the first argument is more general than the second. Atom types must implement this notion of specialization whenever meaningful in the context of the entities being constructed.

The notion of subsumption can be seen as partial equivalence, or equivalence in one direction only.

As a relation, subsumtion is transitive and reflexive. The latter implies that, at a minimum, the subsumes method must return true if general.equals(specific).

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(HGPersistentHandle key)

The key is expected to be of type HGAtomRef OR of type HGHandle. In the former case, references with the specific mode and referent are search. In the latter or if the mode of the HGAtomRef is null, all reference regardless of mode are searched.

Specified by:

find in interface HGSearchable<HGPersistentHandle,HGPersistentHandle>

fromByteArray

public java.lang.Object fromByteArray(byte[] byteArray)

Specified by:

fromByteArray in interface ByteArrayConverter<java.lang.Object>

toByteArray

public byte[] toByteArray(java.lang.Object object)

Specified by:

toByteArray in interface ByteArrayConverter<java.lang.Object>