Program construction is a methodological process that starts from a user’s requirements and end with a working program.
The methodology
Has many different phases.
System level
Covers overall system including hardware, software, users, operating environment, rules and more.
- System requirements analysis
Identify and document the needs and expectations of the users and stakeholders for the system. - System requirements specification
Translate the analyzed requirements into a clear, detailed, and structured document that serves as a reference for development. - System architecture design
Define the overall structure and components of the system, including hardware, software, and interactions, to ensure it meets the specified requirements. - System validation
Verify that the system requirements specification accurately reflects the customer’s needs and expectations.
Software level
Covers software aspect only.
- Software requirements analysis
Examine and understand the needs of the software to ensure alignment with user and system requirements. - Software requirements specification
Document the analyzed requirements in a structured format to guide development and ensure clarity. - Software architecture design
Plan the high-level structure of the software, including components and their interactions, to meet specified requirements. - Software component/module design
Break down the architecture into smaller, manageable modules with detailed designs for implementation. - Program coding and testing
Write the code for the software and test it to ensure functionality and correctness. - Software deployment and maintenance
Release the software to users and provide ongoing updates and fixes to address issues and improve performance. - Software verification
Confirm that the software meets the documented specifications and fulfills its intended purpose.
Requirements
Detailed descriptions of the capabilities, behaviors, and constraints that a system or software must fulfill to meet the needs of its users and stakeholders. Serve as the foundation for all subsequent phases of development.
Functional requirements
A statement of a piece of required functionality or a behavior that a system will exhibit under specific conditions.
The above definition is from Grady Booch, James Rumbaugh, and Ivar Jacobson and is a generally accepted one.
Describes “what” the system should do. Can either be defined by functionality or by behaviour.
Non-functional requirements
Specifies criteria that can be used to judge the operation of a system. Describes “how” the system should perform its functions. Conveniently identified as illities. These are subjetive, ambigous and conflicting.
Examples:
- Usability
- Reliability
- Safety
- Responsiveness
Summary
| Functional req. | Non-functional req. | |
|---|---|---|
| Objective | Describe what product does | Describe how product works |
| End result | Define product features | Define product properties |
| Focus | On user requirements | On user expectations |
| Documentation | Captured in use cases | Captured as a quality attribute |
| Origin type | Defined by user | Defined by developers |