Design Strategies
Definition
Design strategies are the high-level approaches used to derive a software design from the requirements — the overall "game plan" for how a designer moves from the problem (SRS) to the solution (design).
Major Design Strategies
1. Function-Oriented (Process-Oriented) Design
- Focuses on the functions/processes the system performs
- Decomposes the system into functions/sub-functions (top-down)
- Uses Structured Design, DFDs, Structure Charts
- Data and functions are treated separately
2. Data-Oriented Design
- Focuses on data structures first — design is built around how data is organized and flows
- Uses Entity-Relationship models, Jackson Structured Programming (JSP)
3. Object-Oriented Design (OOD)
- Focuses on objects — bundling data (attributes) and behavior (methods) together
- Uses UML diagrams (class, sequence, use case)
- Emphasizes encapsulation, inheritance, polymorphism
4. Component-Based Design
- Assembles the system from pre-built, reusable components
- Emphasizes integration over building from scratch
5. Formal Design (Formal Methods)
- Uses mathematical models to specify and verify design (e.g., Z notation, VDM)
- Rare in industry, common in safety-critical systems (aviation, medical devices)
Comparison
| Strategy | Focus | Best For |
|---|---|---|
| Function-Oriented | Processes/functions | Data-processing systems, legacy systems |
| Data-Oriented | Data structure/flow | Data-centric systems (databases) |
| Object-Oriented | Objects (data+behavior) | Large, complex, evolving systems |
| Component-Based | Reusable components | Rapid development, enterprise systems |
| Formal Methods | Mathematical rigor | Safety-critical, high-assurance systems |
Choosing a Strategy
The choice depends on: problem domain, team expertise, tools available, criticality of the system, and how requirements are structured (function-heavy vs. data-heavy vs. object-heavy).
Exam tip: Be ready to briefly explain each strategy with one example domain, and know that Function-Oriented and Object-Oriented are the two most heavily tested strategies in this syllabus (topics 5 and 11 go deeper into each).