Bug 181121 Model should provide utility method for cube to get correspond dimension key.
In model cube handle, the relation of cube data set and dimension data sets are managed by a series of dimension condition handles.We need model to add utility method so that we can easily get corresponding dimension data set column names according to given cube dimension keys.
model/org.eclipse.birt.report.model/src/org/eclipse/birt/report/model/api/DimensionConditionHandle.java
return getStringProperty( DimensionCondition.HIERARCHY_MEMBER );
	}
	/**
	 * Sets the referred hierarchy by the name.
	 * 
	 * @param hierarchyName
	 *            the hierarchy name to set
	 * @throws SemanticException
	 */
	public void setHierarchy( String hierarchyName ) throws SemanticException
	{
		setProperty( DimensionCondition.HIERARCHY_MEMBER, hierarchyName );
	}
	/**
	 * Sets the referred hierarchy by the handle.
	 * 
	 * @param hierarchyHandle
	 *            the hierarchy handle to set
	 * @throws SemanticException
	 */
	public void setHierarchy( HierarchyHandle hierarchyHandle )
			throws SemanticException
	{
		DesignElement element = hierarchyHandle == null
				? null
				: hierarchyHandle.getElement( );
		setProperty( DimensionCondition.HIERARCHY_MEMBER, element );
	}
}