org.hypergraphdb.algorithms

Class DefaultALGenerator

java.lang.Object

org.hypergraphdb.algorithms.DefaultALGenerator

All Implemented Interfaces:

HGALGenerator, CloseMe

public class DefaultALGenerator
extends Object
implements HGALGenerator, CloseMe

A default implementation of the HGALGenerator that should cover most common cases. In the description below, the term focus atom is used to refer to the atom whose adjacency list is being generated.

The adjacency list generation process is conceptually split into two main steps:

1. Get the relevant links for the atom.
2. For each link, get the relevant members of its outgoing set.

In the simplest case, step 1 amounts to retrieving the incidence set of the focus atom and considering only links that point to other atoms besides it (i.e. links with arity > 1), while step 2 amounts to retrieving all atoms from the currently considered link that are different from the focus atom.

Step 1 may be augmented with a filter to select links only satisfying certain criteria. This filter is configured in the form of a link predicate, a HGQueryCondition.

Step 2 may be configured to treat links as ordered. When links are interpreted as ordered, there are several further options:

• The ordering of the outgoing set may be the one implied by the link instance or its reverse.
• Given the position of the focus atom within a link's outgoing set, the generator may return only the siblings that occur after that position or before or both. Choosing to return both only makes sense when the outgoing set is processed in reverse order, for otherwise the behavior is the same as if a link is treated as unordered.

In addition, step 2 may also filter the sibling atoms by a general predicate similarly to the way links from the incidence set are filtered.

All of the above mentioned options are configured at construction time. In the simplest case of no link or sibling filtering and where links are unordered, use the SimpleALGenerator instead which will be somewhat faster.

Author:

Borislav Iordanov

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
protected class	DefaultALGenerator.AdjIterator

Field Summary

Fields

Modifier and Type	Field and Description
protected HyperGraph	hg

Constructor Summary

Constructors

Constructor and Description
DefaultALGenerator() Default constructor available, but the class is not really default constructible - you must at least specify a HyperGraph instance on which to operate.
DefaultALGenerator(HyperGraph graph) Construct with default values: no link or sibling predicate, returning all siblings in their normal storage order.
DefaultALGenerator(HyperGraph hg, HGAtomPredicate linkPredicate, HGAtomPredicate siblingPredicate) Construct a default adjacency list generator where links are considered unordered.
DefaultALGenerator(HyperGraph hg, HGAtomPredicate linkPredicate, HGAtomPredicate siblingPredicate, boolean returnPreceeding, boolean returnSucceeding, boolean reverseOrder) Construct a default adjacency list generator where links are considered ordered.
DefaultALGenerator(HyperGraph graph, HGAtomPredicate linkPredicate, HGAtomPredicate siblingPredicate, boolean returnPreceeding, boolean returnSucceeding, boolean reverseOrder, boolean returnSource) Construct a default adjacency list generator where links are considered ordered.

Method Summary

Methods

Modifier and Type	Method and Description
void	close()
HGSearchResult<Pair<HGHandle,HGHandle>>	generate(HGHandle h) Return HGSearchResult over all atoms adjacent to the passed in atom.
HyperGraph	getGraph()
HGAtomPredicate	getLinkPredicate()
HGAtomPredicate	getSiblingPredicate()
boolean	isReturnPreceeding()
boolean	isReturnSource()
boolean	isReturnSucceeding()
boolean	isReverseOrder()
DefaultALGenerator	setGraph(HyperGraph graph)
DefaultALGenerator	setLinkPredicate(HGAtomPredicate linkPredicate)
DefaultALGenerator	setReturnPreceeding(boolean returnPreceeding)
DefaultALGenerator	setReturnSource(boolean returnSource)
DefaultALGenerator	setReturnSucceeding(boolean returnSucceeding)
DefaultALGenerator	setReverseOrder(boolean reverseOrder)
DefaultALGenerator	setSiblingPredicate(HGAtomPredicate siblingPredicate)

Methods inherited from class java.lang.Object

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

Field Detail

hg

protected HyperGraph hg

Constructor Detail

DefaultALGenerator

public DefaultALGenerator()

Default constructor available, but the class is not really default constructible - you must at least specify a HyperGraph instance on which to operate.

DefaultALGenerator

public DefaultALGenerator(HyperGraph graph)

Construct with default values: no link or sibling predicate, returning all siblings in their normal storage order.

DefaultALGenerator

public DefaultALGenerator(HyperGraph hg,
                  HGAtomPredicate linkPredicate,
                  HGAtomPredicate siblingPredicate)

Construct a default adjacency list generator where links are considered unordered.

Parameters:

hg - The HyperGraph instance from where incidence sets are fetched.

linkPredicate - The predicate by which links are filtered. Only links satisfying this predicate will be considered. If this parameter is null, all links from the incidence set will be considered.

siblingPredicate - The predicate by which sibling atoms are filtered from the adjacency list. Only atoms satisfying this predicate will be returned. If this parameter is null, all sibling atoms will be considered.

DefaultALGenerator

public DefaultALGenerator(HyperGraph hg,
                  HGAtomPredicate linkPredicate,
                  HGAtomPredicate siblingPredicate,
                  boolean returnPreceeding,
                  boolean returnSucceeding,
                  boolean reverseOrder)

Construct a default adjacency list generator where links are considered ordered.

The constructor does NOT allow both returnSucceeding and returnPreceeding to be set to false. This will always return empty adjacency lists and does not make any sense. Even, in a more complex situation where those parameters are determined at run-time following some unforeseen logic, the caller must make sure that not both of those parameters are false.

Parameters:

hg - The HyperGraph instance from where incidence sets are fetched.

linkPredicate - The predicate by which links are filtered. Only links satisfying this predicate will be considered. If this parameter is null, all links from the incidence set will be considered.

siblingPredicate - The predicate by which sibling atoms are filtered from the adjacency list. Only atoms satisfying this predicate will be returned. If this parameter is null, all sibling atoms will be considered.

returnPreceeding - Whether or not to return siblings that appear before the focus atom in an ordered link.

returnSucceding - Whether or not to return siblings that appear after the focus atom in an ordered link.

reverseOrder - Whether or not to reverse the default order implied by a link's target array. Note that this parameter affects the meaning of preceeding and succeeding in the above two parameters.

DefaultALGenerator

public DefaultALGenerator(HyperGraph graph,
                  HGAtomPredicate linkPredicate,
                  HGAtomPredicate siblingPredicate,
                  boolean returnPreceeding,
                  boolean returnSucceeding,
                  boolean reverseOrder,
                  boolean returnSource)

Construct a default adjacency list generator where links are considered ordered.

The constructor does NOT allow both returnSucceeding and returnPreceeding to be set to false. This will always return empty adjacency lists and does not make any sense. Even, in a more complex situation where those parameters are determined at run-time following some unforeseen logic, the caller must make sure that not both of those parameters are false.

Parameters:

graph - The HyperGraph instance from where incidence sets are fetched.

linkPredicate - The predicate by which links are filtered. Only links satisfying this predicate will be considered. If this parameter is null, all links from the incidence set will be considered.

siblingPredicate - The predicate by which sibling atoms are filtered from the adjacency list. Only atoms satisfying this predicate will be returned. If this parameter is null, all sibling atoms will be considered.

returnPreceeding - Whether or not to return siblings that appear before the focus atom in an ordered link.

returnSucceding - Whether or not to return siblings that appear after the focus atom in an ordered link.

reverseOrder - Whether or not to reverse the default order implied by a link's target array. Note that this parameter affects the meaning of preceeding and succeeding in the above two parameters.

returnSource - Whether to return the source/originating atom along with its siblings. The default is false.

Method Detail

generate

public HGSearchResult<Pair<HGHandle,HGHandle>> generate(HGHandle h)

Description copied from interface: HGALGenerator

Return HGSearchResult over all atoms adjacent to the passed in atom. The result set items are pairs of the form [link, atom] where the first element is the HGLink handle of the link that "leads" to the adjacent atom and the second element is the adjacent atom itself.

Specified by:

generate in interface HGALGenerator

Parameters:

h - The handle of the atom of interest.

close

public void close()

Specified by:

close in interface CloseMe

getGraph

public HyperGraph getGraph()

setGraph

public DefaultALGenerator setGraph(HyperGraph graph)

getLinkPredicate

public HGAtomPredicate getLinkPredicate()

setLinkPredicate

public DefaultALGenerator setLinkPredicate(HGAtomPredicate linkPredicate)

getSiblingPredicate

public HGAtomPredicate getSiblingPredicate()

setSiblingPredicate

public DefaultALGenerator setSiblingPredicate(HGAtomPredicate siblingPredicate)

isReturnPreceeding

public boolean isReturnPreceeding()

setReturnPreceeding

public DefaultALGenerator setReturnPreceeding(boolean returnPreceeding)

isReturnSucceeding

public boolean isReturnSucceeding()

setReturnSucceeding

public DefaultALGenerator setReturnSucceeding(boolean returnSucceeding)

isReverseOrder

public boolean isReverseOrder()

setReverseOrder

public DefaultALGenerator setReverseOrder(boolean reverseOrder)

isReturnSource

public boolean isReturnSource()

setReturnSource

public DefaultALGenerator setReturnSource(boolean returnSource)