In a predictive life cycle, requirements are defined early and in detail before development begins, aligning with the traditional waterfall model. In an agile life cycle, requirements evolve continuously and are refined frequently throughout delivery due to iterative collaboration with stakeholders. For an iterative/incremental life cycle, requirements are revisited and elaborated at periodic intervals, allowing refinement across multiple iterations while maintaining partial system deliveries. This alignment reflects how each approach manages uncertainty, adaptability, and stakeholder engagement.

Project Management Institute (PMI), PMBOK® Guide – Seventh Edition, Section: “Development Approach and Life Cycle Performance Domain,” pp. 53–57.

MIT OpenCourseWare – Agile Software Development (Course 6.170), Lecture Notes on Agile methods, “Requirements elicitation and continuous feedback.”

Stanford University, CS210: Software Project Experience with Corporate Partners – Agile vs. Predictive project planning lectures.

Boehm, B., & Turner, R. (2003). Balancing Agility and Discipline: A Guide for the Perplexed, Addison-Wesley. See Chapter 2 (pp. 25–28).

Highsmith, J. (2002). Agile Software Development Ecosystems, Addison-Wesley. See Section 4.3 (pp. 90–92).