In the two key components the user must design for are object structure and object behavior. In Demeter, these two components are represented by the concepts of class dictionaries and propagation patterns, respectively. Good definitions for these terms and Demeter can be found in The Demeter Users Manual.
Because these concepts form a natural point of separation in the notation,
the most logical view was to split the Isthmus project into two parts.
The first part entailed developing a program which creates the interface for
class dictionaries, and the second part building on the first and extending
it for propagation patterns. The resultant program for class dictionaries
is isthmus-cd which does essentially the same task
as the original tool, isthmus. However isthmus-cd goes beyond the
previous functionality, and adds the necessary setup for generating the
interface code for
propagation patterns. Therefore if the users final goal is to use
propagation patterns, then she must use this tool first,
and not isthmus.