Editing Waterfall model (section)

==Model==
Although Royce never recommended nor described a waterfall model,<ref name="inheriting_agile">{{cite book |last1=Lineberger |first1=Rob |title=Inheriting Agile: The IT Practitioner's Guide to Managing Software Development in a Post-Agile World |date=Apr 25, 2024 |publisher=Sandprint Press |location=Durham, NC |isbn=9798989149605 |page=37 |url=https://books.google.com/books?id=kTit0AEACAAJ}}</ref> rigid adherence to the following phases are criticized by him:
# [[System requirements|System]] and [[software requirements]]: captured in a [[product requirements document]]
# [[Requirements analysis|Analysis]]: resulting in [[Model-driven software development|models]], [[Database schema|schema]], and [[business rule]]s
# [[Software design|Design]]: resulting in the [[software architecture]]
# [[Computer programming|Coding]]: the [[software development|development]], [[Unit testing|proving]], and [[System integration|integration]] of software
# [[Software testing|Testing]]: the systematic discovery and [[debugging]] of [[Software bug|defects]]
# [[Computer operator|Operations]]: the [[Installation (computer programs)|installation]], [[Data migration|migration]], [[Technical support|support]], and [[software maintenance|maintenance]] of complete systems

Thus, the waterfall model maintains that one should move to a phase only when its preceding phase is reviewed and verified.

Various [[#Modified waterfall models|modified waterfall models]] (including Royce's final model), however, can include slight or major variations on this process.<ref name="royce" /> These variations include returning to the previous cycle after flaws are found downstream, or returning to the design phase if downstream phases are deemed insufficient.