/*
 * Hibernate, Relational Persistence for Idiomatic Java
 *
 * License: GNU Lesser General Public License (LGPL), version 2.1 or later.
 * See the lgpl.txt file in the root directory or <http://www.gnu.org/licenses/lgpl-2.1.html>.
 */
package org.hibernate.loader.plan.spi;

Represents the circular side of a bi-directional entity association. Wraps a reference to the associated
(target) EntityReference.
 The EntityReferenceAliases for this object is the same as for its target EntityReference, and can be looked up via AliasResolutionContext.resolveEntityReferenceAliases(String) using the value returned by getQuerySpaceUid(). This relies on reference lookups against the EntityReference instances, therefore this allows representation of the circularity but with a little protection against potential stack overflows. This is unfortunately still a cyclic graph. An alternative approach is to make the graph acyclic (DAG) would be to follow the process I adopted in the original HQL Antlr v3 work with regard to always applying an alias to the "persister reference", even where that meant creating a generated, unique identifier as the alias. That allows other parts of the tree to refer to the "persister reference" by that alias without the need for potentially cyclic graphs (think ALIAS_REF in the current ORM parser). Those aliases can then be mapped/catalogued against the "persister reference" for retrieval as needed. 
Author:
Steve Ebersole/**
 * Represents the circular side of a bi-directional entity association. Wraps a reference to the associated
 * (target) EntityReference.
 * <p/>
 * The {@link org.hibernate.loader.plan.exec.spi.EntityReferenceAliases} for this object is the same as
 * for its target EntityReference, and can be looked up via
 * {@link org.hibernate.loader.plan.exec.spi.AliasResolutionContext#resolveEntityReferenceAliases(String)}
 * using the value returned by {@link #getQuerySpaceUid()}.
 *
 * This relies on reference lookups against the EntityReference instances, therefore this allows representation of the
 * circularity but with a little protection against potential stack overflows.  This is unfortunately still a cyclic
 * graph.  An alternative approach is to make the graph acyclic (DAG) would be to follow the process I adopted in the
 * original HQL Antlr v3 work with regard to always applying an alias to the "persister reference", even where that
 * meant creating a generated, unique identifier as the alias.  That allows other parts of the tree to refer to the
 * "persister reference" by that alias without the need for potentially cyclic graphs (think ALIAS_REF in the current
 * ORM parser).  Those aliases can then be mapped/catalogued against the "persister reference" for retrieval as needed.
 *
 * @author Steve Ebersole
 */
public interface BidirectionalEntityReference extends EntityReference {
	
Get the targeted EntityReference
Returns:
The targeted EntityReference/**
	 * Get the targeted EntityReference
	 *
	 * @return The targeted EntityReference
	 */
	public EntityReference getTargetEntityReference();

	
The query space UID returned using getQuerySpaceUid() must be the same as returned by #getTargetEntityReference()#getQuerySpaceUid() 
Returns:
The query space UID./**
	 * The query space UID returned using {@link #getQuerySpaceUid()} must
	 * be the same as returned by {@link #getTargetEntityReference()#getQuerySpaceUid()}
	 *
	 * @return The query space UID.
	 */
	public String getQuerySpaceUid();
}