# Waterfall ## Basic idea The original plan-driven SDLC: sequential phases (requirements → design → implementation → verification → maintenance), each fully completed before the next begins. Strong if requirements are fixed; brittle if they aren't. ## Key facts * Requirements frozen at the start. * Phase-by-phase, no overlap. * Heavyweight up-front planning ⇒ accurate budgets if everything else holds. * Painful to accommodate change late. * Traditional approach used for over 40 years. * Requirements must be defined at the start. * Little / no alternations. * Sequential - Complete 1 task and then the next. * Used in large scale SW development where thorough planning and predictability is required. ## Pros * Extensive planning, this thoroughness often results in more accurate timelines and budgets. ## Cons * Difficult to apply changes or modify / correct previous steps --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://isubasinghe.gitbook.io/isithas-wiki/software_engineering/management/process_and_management/waterfall.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.