Software Processes

COMP201 Lectures 2021-09-29

Requirements Engineering & Specification

Software specification is the process of establishing what services are requires and the constraints on the system’s operation and development.

Requirements Engineering Process

flowchart LR
fs([Feasibility Study]) --> re([Requirements Elicitation & Analysis]) <--> rs([Requirements Specification]) <--> rv([Requirements Validation])
fs --> fr[Feasibility Report]
re --> sm[System Models]
rs --> usr[User & System Requirements]
sm --> rd[Requirements Document]
usr --> rd

Software Design & Implementation

This is the process of converting the system specification into an executable system. This includes:

1. Software Design
   • Design a software structure that realises the specification.
   • There are many tasks that comprise this section.
2. Implementation
   • Translate this structure into an executable program.

Design and implementation are closely related and may be inter-leaved.

Design Process Activities

1. Architectural Design (Separating web service modules)
   • Sub-systems making up the ystem and their relationships are identified and documented.
2. Abstract Specification
   • For each sub-system, an abstract specification of its operation constraints and services is produces.
3. Interface Design
   • For each sub-system, an unambiguous interface with other sub-systems is designed and documented.
4. Components Design
   • Services are allocated to components and the interfaces of these components are desgned.
5. Data Structure Design
   • The data structures used in the system implementation are designed in detail and specified.
6. Algorithm Design
   • The algorithms used in components to provide services are designed and specified.

Design Methods

Design methods are systematic approaches to developing a software design. This design is usually documented as a set of graphical models.

You could use the following types of model:

• Data-flow
• Entity relation attribute model.
• Structural Model
• Object Models
• State Transition Model (Showing system states and triggers)

Programming & Debugging

Programming should be an iterative activity where small pieces are written and testing is completed.

Testing

flowchart LR
ut[Unit Testing] <--> mt[Module Testing] <--> st[Sub-system Testing] <--> sst[System Testing] <--> at[Acceptance Testing]
subgraph Component Testing
ut
mt
end
subgraph Integration Testing
st
sst
end
subgraph User Testing
at
end

The prior stages are described as:

1. Unit Testing - Individual components are tested.
   • Testing classes.
2. Module Testing - Related collections of dependent components are tested.
   • Testing class integration.
3. Sub-system Testing - Modules are integrated into sub-systems and tested. The focus here should be on interface testing.
   • Testing classes as a service. An organised package or JAR library.
4. System Testing - Testing of the system as a while. Testing of emergent properties.
   • Whole system test.
5. Acceptance Testing - Testing with customer data to check that it is acceptable.