Coupling¶

The degree to which one module depends on internal details of another determines how changes propagate through the system

Tension Addressed¶

Coupling vs. Flexibility

Recognizable As¶

Import/dependency graphs; shared data structures; temporal dependencies (A must run before B); knowledge of internal state; ripple effects when changing one component

Canonical Sources¶

Stevens, Myers, Constantine, "Structured Design" (1974); Yourdon & Constantine, "Structured Design" (1979)

Transfers To¶

Organizational Design (Conway's Law), Distributed Systems (service boundaries), Testing (test isolation), Database Design (table relationships)

Sub-concepts: - Content coupling: Worst - module modifies another's internals directly - Common coupling: Sharing global data - Control coupling: Passing control flags that change behavior - Stamp coupling: Passing whole structures when only part is needed - Data coupling: Best - passing only necessary data through parameters