Decomposition

Decomposition in computer science, also known as factoring, is breaking a complex problem or system into parts that are easier to conceive, understand, program, and maintain.

Stages of decomposition by programming teams

• 1. Brainstorming (Brainstorming to locate possible classes) 

     1. • the stage in which we make a first pass at determining the classes in the problem.

  2. Filtering (Filtering the classes to find duplicates or remove unnecessary ones) 

     1. • the stage in which we go back over the proposed classes determined in the brainstorming stage to see if any can be combined or if any are missing. 

        • Each class that survives the filtering stage is examined more carefully in the next stage.

  3. Scenarios (Scenarios are tried to be sure we understand collaborations) 

     1. • is the stage in which the behaviour (methods/functions) of each class is determined. Because each class is responsible for its own behaviour, we call these behaviours responsibilities

  4. Responsibility algorithms: (Responsibility algorithms are designed for all actions that classes must exhibit) 

     1. • a stage in which the algorithms are written for the responsibilities for each of the classes.

Types of decomposition defined in computer science

• • In structured programming, algorithmic decomposition breaks a process down into well-defined steps.

  • Structured analysis breaks down a software system from the system context level to system functions and data entities

  • Object-oriented decomposition, on the other hand, breaks a large system down into progressively smaller classes or objects that are responsible for some part of the problem domain.

  • According to Booch, algorithmic decomposition is a necessary part of object-oriented analysis and design, but object-oriented systems start with and emphasize decomposition into classes.

Decomposition in Programming

How computer programmers use decomposition

Computer programmers do exactly the same thing. When they are writing a program they often break the code into small chunks.

They call this approach 'decomposition' because you are ‘decomposing’ or breaking down a large problem into smaller problems.

Decomposition saves a lot of time: the code for a complex program could run to many lines of code. If a mistake was made it would take a very long time to find.

Re-using code

Another benefit to decomposition is that it allows programmers to easily copy and reuse useful chunks of code for other programs.