public static <T,U> TemporalExprViewItem<T> expr( String exprId, Variable<T> var1, Variable<U> var2, TemporalPredicate temporalPredicate ) {
        return new VariableTemporalExprViewItem<>( exprId, var1, null, var2, null, temporalPredicate);
    }
public static < T , U > TemporalExprViewItem < T > expr ( String exprId , Variable < T > var1 , Variable < U > var2 , TemporalPredicate temporalPredicate ) { return new VariableTemporalExprViewItem < > ( exprId , var1 , null , var2 , null , temporalPredicate ) ; }
-- Temporal Constraints --