Question

Explain the type of coupling (and hence dependencies) that can be expected for task services, utility services, and entity services. How does coupling at the service level affect the capabilities of the service that is dependent on either external or internal implementations?

Answer 1

A module having high cohesion and low coupling is said to be functionally independent of other modules. Coupling is the measure of the degree of interdependence between the modules. A good software will have low coupling.

So the types of coupling are:

1.data coupling

2. stamp coupling

3. control coupling

4. external coupling

5. common coupling

Explanations of these are:

1. data coupling: the components are independent to each other and communicating through data. Module communications don’t contain tramp data.

Two modules are data coupled, if they communicate through a parameter.

E.g. an integer, a float, a character, etc.

2.  stamp coupling: the complete data structure is passed from one module to another module.When multiple modules share common data structure and work on different part of it.

3. Two modules are called control-coupled if one of them decides the function of the other module or changes its flow of execution.It can be bad if parameters indicate completely different behavior and good if parameters allow factoring and reuse of functionality. Example- sort function that takes comparison function as an argument, a flag set in one module and tested in another module.

4. the modules depend on other modules, external to the software being developed or to a particular type of hardware. Ex- protocol, external file, device format, etc.

5. The modules have shared data such as global data structures.