Generally, we formulate consistency conditions of layered graph grammars
similar to non-layered grammars. But sometimes, it can be useful to define
some common consistency conditions and/or some consistency conditions
for a certain layer. Consistency conditions for a certain layer should be
satisfied during graph transformations on this layer only.
On the other hand, consistency conditions without any layer shoud be satisfied
for all layers.
Choosing menu item Set Constraint Layer of submenu Layering of pop-up menu GraGra you will get a table with consistency conditions and layers where you can set one or more layers for each consistency condition or let it without any layer.