A cyclical methodology, informally known as the spiral, fixes some of the problems introduced by a sequential methodology. A cyclical methodology still has the four phases. A little time is initially spent in each phase, followed by several iterations over all four phases.
Simply, the methodology iterates over the processes of think a little, plan a little, implement a little, then test a little. The document structures and deliverable types from each phase incrementally change in structure and content with each cycle or iteration. More detail is generated as the methodology progresses. Finally, after several iterations, the product is complete and ready to ship. The cyclical methodology may continue shipping multiple versions of the product. Ideally, each phase is given equal attention. See Figure 3.2 on page .