org.jrdf.query.relation.constants
Class RelationDEE

java.lang.Object
  org.jrdf.query.relation.constants.RelationDEE

All Implemented Interfaces:

Serializable, Relation

public final class RelationDEE
extends Object
implements Relation, Serializable

Dee is a relation with one tuple and is the base relation for NULLARY_TUPLE.

It is also the identity with respect to JOIN i.e. JOIN {r, RelationDEE} is DEE and JOIN {} is RelationDEE.

Again, this is going to change when operations are more properly filled out.

Version:

$Revision: 1048 $

Author:

Andrew Newman

See Also:

Serialized Form

Field Summary

static Relation

RELATION_DEE The singleton version of RelationDEE.

Method Summary

Set<Attribute>	getHeading() Returns the set of attributes or heading of the relation.
SortedSet<Attribute>	getSortedHeading()
SortedSet<Tuple>	getSortedTuples()
Set<Tuple>	getTuples() Returns the TUPLE_ZERO.

Methods inherited from class java.lang.Object

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

Field Detail

RELATION_DEE

public static final Relation RELATION_DEE

The singleton version of RelationDEE.

Method Detail

getHeading

public Set<Attribute> getHeading()

Description copied from interface: Relation

Returns the set of attributes or heading of the relation.

Specified by:

getHeading in interface Relation

Returns:

the set of attributes or heading of the relation.

getTuples

public Set<Tuple> getTuples()

Returns the TUPLE_ZERO.

Specified by:

getTuples in interface Relation

Returns:

the TUPLE_ZERO.

getSortedHeading

public SortedSet<Attribute> getSortedHeading()

Specified by:

getSortedHeading in interface Relation

getSortedTuples

public SortedSet<Tuple> getSortedTuples()

Specified by:

getSortedTuples in interface Relation