Bug 184762 BIRT Model - Enhancments to the level defintion
xtab/org.eclipse.birt.report.item.crosstab.core/src/org/eclipse/birt/report/item/crosstab/core/ILevelViewConstants.java
{
	/**
	 * Name of the property that refers a OLAP level element.
	 */
	String LEVEL_PROP = "level"; 
	/**
	 * Name of the property that defines some filter conditions.
	 */
	String FILTER_PROP = "filter"; 
	/**
	 * Name of the property that indicates the sort type.
	 */
	String SORT_TYPE_PROP = "sortType"; 
	/**
	 * Name of the property that indicates the sort direction of this level.
	 */
	String SORT_DIRECTION_PROP = "sortDirection";