Selection of a Life Cycle Model

Public section

Theme Text

Preferences are saved on this device.

Choosing an Appropriate Software Process Model

Choosing an appropriate software life cycle model is a critical project decision. The selected model influences cost, schedule, quality, and even the probability of project success. No single model is best for all projects; the choice depends on several situational factors.

Nature of Requirements

Are requirements clear and stable, or vague and likely to change?
Are they already well-documented, or still evolving through user discussion and prototyping?

Experience and Technical Knowledge of the Development Team

Is the team familiar with the application domain and technology stack?
Do they have experience with iterative, agile, or risk-driven models?

User Involvement

How frequently can users or domain experts participate in the project?
Is continuous feedback available, or only limited interaction at key milestones?

Type of Project

Is it a completely new system, or an enhancement/port of an existing product?
Maintenance and extension tasks often suit incremental or evolutionary approaches.

Project Schedule

Is the timeline tight and fixed, or relatively flexible?
Are staged deliveries or early partial releases required?

Budget Constraints

Is the budget fixed and limited?
Can funding be adjusted later based on results and feedback?

Risk Level

What are the technical, financial, and operational risks involved?
High-risk projects often benefit from risk-driven models such as the Spiral Model, which support early risk identification, analysis, and mitigation.

Examples of Model Selection

When the Waterfall Model is Appropriate

Requirements are well understood and stable from the start.
The development team is experienced with the technology and the domain.
User participation is limited after the requirements phase.
Funding is stable, and the organization prefers formal documentation and milestone-based control.

When Evolutionary Models are Suitable

The system is relatively complex, but requirements do not change very frequently.
Some user feedback is needed, but continuous end-user involvement is not practical.
The development team is new to the technology and needs to learn and refine the solution through iterations (possibly with initial domain training).

Table 1: Comparison of Incremental, Spiral, Prototyping and V-Model

Aspect	Incremental Model	Spiral Model	Prototyping Model	V-Model (V-Shaped)
Core Idea	System is delivered in a series of increments (versions); each increment adds more functionality.	Risk-driven iterative cycles; each loop covers objectives, risk analysis, development and evaluation.	Build a partial prototype (throwaway or evolving) to clarify requirements before full-scale development.	Extension of waterfall: each development phase has a corresponding test phase (verification ↔ validation).
Requirements Situation	Most major requirements are known early; some details may evolve over time.	Requirements are unclear, evolving, or contain many unknowns.	Requirements are poorly understood; users are unsure what they want.	Requirements are stable and well defined from the beginning.
Risk Handling	Medium – each increment reduces risk by delivering and testing part of the system.	Strong, explicit risk analysis in every cycle; risk is the main driver of the process.	Reduces requirement and usability risk through early user experimentation with the prototype.	Limited explicit risk handling; emphasis is on systematic testing rather than detailed risk analysis.
User Involvement	Periodic feedback at the end of each increment.	Regular customer evaluation at the end of each spiral cycle.	High, especially during prototype evaluation and refinement.	Mainly at the requirements phase and during User Acceptance Testing; not continuous.
Typical Use / Suitability	Large systems where core features are needed early and the system can be logically split into increments.	Medium to high-risk, complex or innovative projects; new product lines.	UI-intensive systems, new concepts, or projects where requirement clarification is the primary goal.	Safety-critical or high-reliability systems (e.g., medical, aerospace) needing strong documentation and formal testing.