Prescriptive Process Models Developed to bring order and structure to the software development process. To get away from the chaos of most development processes. But there is a strange balance between order and chaos. Absolute order means absence of variability. Absolute chaos makes coordination and coherence impossible. Thus, a balance is needed.

Need for balance between order and chaos Chaos leaves alternatives open, change is easier, thinking outside the box, creativity often thrives better in chaos. Order keeps things on task, on schedule, things are documented, structure is maintained. To a considerable degree, this philosophical question continues to be debated. Individuals are right- and left-brained. The left is order, the right is creativity.

Waterfall Model Waterfall Method – A series of steps where each steps falls to the next step. –Communication –Planning –Modeling –Construction –Deployment

Incremental Model Follows the waterfall model but does so in repeated steps. First step gets a quick version that does part of project. Second increment gets a better, more detailed version. Successive increments get better and more complete software.

RAD Model Rapid Application Development – an incremental model that emphasizes a short development cycle. Uses component-based construction method. Does not work for all projects… particularly large projects or when project is high risk.

Evolutionary Process Models Software evolves over time (web pages are a prime example) Limited version is needed to meet business pressures. Time does not allow a full and complete system to be developed. Evolutionary models are iterative as software engineers develop increasingly more complete and complex systems

Prototyping Prototypes are built when goals are general and not specific. Prototyping can be used as a standalone process or by one of the processes presented. The prototype serves as the first system. Users get a feel for the actual system and devleopers get something built quickly. A prototype is intended for short term use but too often they are used much longer.

The Spiral Model An evolutionary model that couples the iterative nature of prototyping with the controlled, systematic aspects of waterfall model. Spiral model is often developed in a series of releases or versions. Is Adobe or Microsoft working on new releases? Better for large projects.

Concurrent Development Model All activities exist concurrently but are in different states. Some activities are in full production while others are awaiting changes. As events occur, then the flow works forward into the system.

Specialized Process Models Special Process Models take many of the characteristics of the previous models shown. Special Process Models tend to be used when a narrowly defined Software Engineering Approach is chosen.

Component Based Development COTS or Commercial Off-The-Shelf components are becoming more available. Most (not all) COTS components have targeted functionality with good interfaces that enable the component to be integrated. This approach incorporates many of the aspects of the spiral model. This approach has support of government:

Formal Methods Development Model Formal mathematical specification of the software. Specify, develop and verify by rigourous math notation. Eliminates ambiguity, incompleteness, and inconsistency. Used more where safety-critical software is developed, e.g., aircraft avionics, medical devices, etc.

Aspect-Oriented SW Development Nearly all SW has localized features, functions and information content. User or customer concerns or needs must be included. These can be high-level concerns like security or lower-level such as marketing business rules or systemic such as memory management. Aspect-Oriented process is new and still developing.