Working with Concept Modeling

Apply concept modeling principles to design, implementation, and maintenance by defining independent concepts around user purposes and coordinate their collaboration with synchronization rules.

Follow the structural pattern proposed by Daniel Jackson and Eagon Meng: build applications from concepts and synchronizations. Concepts are fully independent services; synchronizations are event-based rules that mediate between them.

Purpose

• One concept, one clear user-facing purpose.
• Fulfill the purpose with complete behavior.
• Use a representative behavioral history to explain how the purpose is fulfilled; define behavior through state and action specifications.

Independence

• Each concept manages its own state; mutable state is not shared.
• Concepts are independently understandable; they neither invoke other concepts’ actions nor query their state.
• Keep references to external objects polymorphic, without depending on their concrete types or internal structure.

Composition

• Concepts define behavior; synchronizations define collaboration.
• Synchronizations match action completions, query the required state, and invoke subsequent actions.
• Application-specific cross-concept rules belong in synchronizations, which depend only on concept specifications.
• Composed behavior must still conform to each concept’s specification.

Engineering additions

The following implementation and maintenance conventions belong to this skill; they are not presented as the authors’ original wording or distinctive principles.

Implementation

• Actions uphold preconditions, outcomes, and invariants.
• Make the observable outcomes of failure, retries, and concurrency explicit.
• Verify concept contracts and composition purposes separately.

Maintenance

• Determine responsibility before adding structure.
• Preserve behavior when refactoring; make intentional changes explicit.
• Limit changes to what is needed; retain clear code.