Cohesion (interdependency within module) strength/level names : (from worse to better, high cohesion is good)
- Coincidental Cohesion : (Worst) Module elements are unrelated
- Logical Cohesion : Elements perform similar activities as selected from outside module, i.e. by a flag that selects operation to perform (see also CommandObject).
i.e. body of function is one huge if-else/switch on operation flag
- Temporal Cohesion : operations related only by general time performed (i.e. initialization() or FatalErrorShutdown?())
- Procedural Cohesion : Elements involved in different but sequential activities, each on different data (usually could be trivially split into multiple modules along linear sequence boundaries)
- Communicational Cohesion : unrelated operations except need same data or input
- Sequential Cohesion : operations on same data in significant order; output from one function is input to next (pipeline)
- Informational Cohesion: a module performs a number of actions, each with its own entry point, with independent code for each action, all performed on the same data structure. Essentially an implementation of an abstract data type.
i.e. define structure of sales_region_table and its operators: init_table(), update_table(), print_table()
- Functional Cohesion : all elements contribute to a single, well-defined task, i.e. a function that performs exactly one operation
get_engine_temperature(), add_sales_tax()
Coupling (interdependence between modules) level names: (from worse to better, high coupling is bad)
- Content/Pathological Coupling : (worst) When a module uses/alters data in another
- Control Coupling : 2 modules communicating with a control flag (first tells second what to do via flag)
- Common/Global-data Coupling : 2 modules communicating via global data
- Stamp/Data-structure Coupling : Communicating via a data structure passed as a parameter. The data structure holds more information than the recipient needs.
- Data Coupling : (best) Communicating via parameter passing. The parameters passed are only those that the recipient needs.
- No data coupling : independent modules.