Bug 176436 Charts Imported from Libraries do not update when libraries change
During a live presentation of BIRT at EclipseCon, we came across a rather embarassing issue. When charts are included in a library, and imported into a report design from a library, any changes to the library instance of the chart do not reflect in the report itself.
model/org.eclipse.birt.report.model/src/org/eclipse/birt/report/model/api/GroupPropertyHandle.java
protected ElementPropertyDefn propDefn = null;
	/**
	 * Handle to a collection of elements.
	 */
	protected GroupElementHandle handle = null;
	/**
	 * Constructs a handle to deal with an common property within a group of
	 * elements. The given property definition should be a common property
	 * shared by the collection of elements.
	 * 
	 * @param handle
	 *            Handles to a collection of elements.
	 * @param propDefn
	 *            definition of the property.
	 */
	GroupPropertyHandle( GroupElementHandle handle, ElementPropertyDefn propDefn )
	{
		assert propDefn != null;
		assert handle instanceof SimpleGroupElementHandle;
		this.handle = handle;
		this.propDefn = propDefn;
	}
	/**
	 * Indicates whether the group of element share the same value for this
	 * property.
	 * <p>
	 * If all element has a <code>null</code> value for this property, it is
	 * considered that they share the same value.
	 * 
	 * @return <code>true</code> if the group of element share the same value.