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/core/Structure.java
import org.eclipse.birt.report.model.api.metadata.IObjectDefn;
import org.eclipse.birt.report.model.api.metadata.IPropertyType;
import org.eclipse.birt.report.model.api.metadata.IStructureDefn;
import org.eclipse.birt.report.model.metadata.ElementRefPropertyType;
import org.eclipse.birt.report.model.metadata.ElementRefValue;
import org.eclipse.birt.report.model.metadata.MetaDataDictionary;
import org.eclipse.birt.report.model.metadata.PropertyDefn;
import org.eclipse.birt.report.model.metadata.StructPropertyDefn;
import org.eclipse.birt.report.model.util.ModelUtil;
import org.eclipse.birt.report.model.util.ReferenceValueUtil;
/**
 * Base class for property structures. Implements the two "boiler-plate" methods
 * from the IStructure interface.
 * 
 */
public abstract class Structure implements IStructure
{
	private StructureContext context;
	/*
	 * (non-Javadoc)
	 * 
	 * @see java.lang.Object#equals(java.lang.Object)
	 */
	public boolean equals( Object obj )
	{
		if ( !( obj instanceof Structure ) )
			return false;
		Structure struct = (Structure) obj;
		if ( struct.getDefn( ) != getDefn( ) )
			return false;