The document discusses four systems and suggests appropriate software process models for managing their development: 1. An anti-lock braking system is safety-critical, so the waterfall model is appropriate due to its formal transformations and proof requirements. 2. A virtual reality maintenance system has unpredictable requirements, so the exploratory programming model is suitable. 3. A university accounting system replaces an existing system, so the waterfall model is appropriate due to stable requirements. 4. A train time inquiry system has complex user interfaces but must be stable and reliable. It should use throw-away prototyping followed by incremental development or waterfall.