A rule consists of a left hand side (LHS), a right hand side (RHS)
and a morphism from LHS to RHS which maps part of the LHS to RHS.
Editing a rule, it is advisable to draw the objects of the left-hand rule side first, and then choose
menu item Identic Rule in menu Edit. The graph objects of the left-hand rule side
are then copied to the right-hand rule side, and an identic rule morphism is generated. The rule morphism is indicated
in the editor by showing identic numbers for each graph object on the left-hand side and its image
on the right-hand side of the rule. Now, having two identic rule sides, the graph objects that are to be deleted
by the rule, have to be deleted in the right-hand rule side, and graph objects that are to be created
by the rule have to be drawn there additionally. Another possibility to draw the same rule would be to draw the
part of the left-hand rule side first that is to be preserved by the rule, then choose Identic Rule and
afterwards add those graph objects to the left-hand rule side that are to be deleted and those
graph objects to the right-hand rule side that are to be created by the rule.
An alternative to define a rule morphism is to draw both rule
sides first, and then change to the edit mode Map.
In this mode, the rule morphism can be defined elementwise by
clicking on a graph object in the left-hand rule side first,
and then clicking
on a graph object of the same type in the right-hand rule side. This method
is useful when there is already a rule morphism and the user wants to change it.
One can define an injective or non-injective rule morphism.
A non-injective mapping of objects is indicated by several
numbers in the target object to which several source objects
are mapped to.
To delete the mappings of a rule morphism
the edit mode Unmap can be used and then click on a certain graph object.
Analogously, a NAC may be entered by drawing graph objects into the NAC graphical editor
and then defining the mappings from the left-hand rule side to the NAC by the Edit Mode Map
clicking elementwise on a graph object in the left-hand rule side first, and then clicking
on a graph object of the same type in the NAC graph. In addition to mapping graph objects of
the same type it is possible to map a LHS object to a more refined type in the NAC graph,
if there is a parent child relation
between those types.
Using menu item Identic NAC of menu Edit functions
similar to menu item Identic Rule.