CMP.14:1 - Problem frame

Use this when computations that work separately must run together, but shared state, communication or scheduling can change their results. You need to construct their interaction, repair a failing interleaving, or replace a component while retaining the behavior on which the rest relies.

The reader can describe each component’s operations and the results expected from their combination. This method adds the shared state, communication and ordering rules needed to reason about the whole. It applies to concurrent algorithms and protocols, including computations performed by cooperating software agents. The implementation language and physical machine supply particular operations and failure conditions.

The first useful result is a composed procedure with a trace or invariant explaining how it obtains the required observation, or a counterexample that identifies the interaction to change. A small shared-state example needs only a few explicit steps. A general guarantee over an implementation needs the corresponding memory, scheduling and failure assumptions.

Use ordinary sequential composition or dependency scheduling when completed outputs suffice and no relevant interference remains. If the algorithms are already adequate and only their physical communication or timing is unresolved, take those requirements to the realization method. An organizational division of work needs its own account of actual roles, capabilities and authority; a computational model can help compare it once that correspondence is established.