import java.util.Vector;

/*
 * Edge is the edge between nodes of a query.
 * It consists of uniquer ID, names of 2 relations that it connects &
 * a vector of ZExpressions ( join predicates )
 * Each ZExpression consists of an operator(String) and operands(a vector of two ZConstant)
 */
public class Edge
{

private int EdgeID;
private String relations[];
private Vector joinPredicates;  // a vector of type ZExpression

}