org.hypergraphdb.type

Class SlotType

java.lang.Object

org.hypergraphdb.type.SlotType

All Implemented Interfaces:

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

public final class SlotType
extends Object
implements HGCompositeType, HGSearchable<Slot,HGPersistentHandle>

The SlotType handles atoms of type Slot. Slots are used to build up record types.

IMPLEMENTATION NOTE: Eventually, it will be useful to be able to search by slot name or slot value type only. To support this, it's probably best to create a separate index for each component. Also, index management should probably be updated once we have more flexible two-way indexes that represent a 1-1 mapping (so that a key may be efficiently searched by the value of the index entry); right now, removal of a slot is implemented by first constructing the Slot instance...(which is ok as long as this removal is not performed very often).

Author:

Borislav Iordanov

Field Summary

Fields

Modifier and Type	Field and Description
static String	INDEX_NAME
static String	LABEL_DIMENSION
static String	VALUE_TYPE_DIMENSION

Constructor Summary

Constructors

Constructor and Description
SlotType()

Method Summary

Methods

Modifier and Type	Method and Description
HGSearchResult<HGPersistentHandle>	find(Slot 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 hg) 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 generic semantic predicate that returns true if the first argument is more general than the second.

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

LABEL_DIMENSION

public static final String LABEL_DIMENSION

See Also:

Constant Field Values

VALUE_TYPE_DIMENSION

public static final String VALUE_TYPE_DIMENSION

See Also:

Constant Field Values

Constructor Detail

SlotType

public SlotType()

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 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)

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(Slot 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<Slot,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.