It is necessary to select a quarter (or subregion) resulting from the Grid rule. Instead of a single label, a list of expressions paired with labels are now allowed – when expression matches a given quarter – label is selected. At the end there should be a label without expression to guarantee a label for for a quarter that has not been matched by the other expressions.

For instance instead of:

**Park ->(…){ ParkQuarter }**

It is possible to have:

**Park ->(…)**{ ParkQuarter | 0, 1, Quarter2 | odd, 1, Quarter3 }

In other words we replace *label* with *label_list*:

*label_list* = *label_expr* ( ‘|’ *label_expr* )*

** label_expr = label | x_idx_expr ‘,’ y_idx_expr ‘,’ label**

*x_idx_expr*,*y_idx_expr*= [‘!’] idx_expr

*idx_expr*= NUM | ‘odd’ | ‘border’Where index expression is either a number or a constant label which corresponds to multiple indexing of being either odd, on the boundary. We could also have a negation of an expression. However negation applies to individual axes, for instance “!x, !y, Label” negates **both** x and y.