Software Engineering-Software Prototyping


Analysis should be conducted regardless of the software engineering paradigm that is applied. However, the form that analysis takes will vary. In some cases it is possible to apply operational analysis principles and derive a model of software from which a design can be developed. In other situations, requirements elicitation (via FAST, QFD, use-cases, or other "brainstorming" techniques ) is conducted, analysis principles are applied, and a model of the software to be built, called a prototype, is constructed for customer and developer assessment. Finally, some circumstances require the construction of a prototype at the beginning of analysis, since the model is the only means through which requirements can be effectively derived. The model then evolves into production software. 

Selecting the Prototyping Approach

The prototyping paradigm can be either close-ended or open-ended. The close-ended approach is often called throwaway prototyping. Using this approach, a prototype serves solely as a rough demonstration of requirements. It is then discarded, and the software is engineered using a different paradigm. An open-ended approach, called evolutionary prototyping, uses the prototype as the first part of an analysis activity that will be continued into design and construction. The prototype of the software is the first evolution of the finished system.

Before a close-ended or open-ended approach can be chosen, it is necessary to determine whether the system to be built is amenable to prototyping. A number of prototyping candidacy factors can be defined: application area, application complexity, customer characteristics, and project characteristics.

In general, any application that creates dynamic visual displays, interacts heavily with a user, or demands algorithms or combinatorial processing that must be developed in an evolutionary fashion is a candidate for prototyping. However, these application areas must be weighed against application complexity. If a candidate application (one that has the characteristics noted) will require the development of tens of thousands of lines of code before any demonstrable function can be performed, it is likely to be too complex for prototyping. If, however, the complexity can be partitioned, it may still be possible to prototype portions of the software.

Because the customer must interact with the prototype in later steps, it is essential that (1) customer resources be committed to the evaluation and refinement of the prototype and (2) the customer is capable of making requirements decisions in a timely fashion. Finally, the nature of the development project will have a strong bearing on the efficacy of prototyping. 

Prototyping Methods and Tools

For software prototyping to be effective, a prototype must be developed rapidly so that the customer may assess results and recommend changes. To conduct rapid prototyping, three generic classes of methods and tools  are available:

Fourth generation techniques. Fourth generation techniques (4GT) encompass a broad array of database query and reporting languages, program and application generators, and other very high-level nonprocedural languages. Because 4GT enable the software engineer to generate executable code quickly, they are ideal for rapid prototyping.

Reusable software components. Another approach to rapid prototyping is to assemble, rather than build, the prototype by using a set of existing software components. Melding prototyping and program component reuse will work only if a library system is developed so that components that do exist
can be cataloged and then retrieved. It should be noted that an existing software
product can be used as a prototype for a "new, improved" competitive
product. In a way, this is a form of reusability for software prototyping.

Formal specification and prototyping environments. Over the past two decades, a number of formal specification languages and tools have been developed as a replacement for natural language specification techniques. Today, developers of these formal languages are in the process of developing
interactive environments that (1) enable an analyst to interactively create language-based specifications of a system or software, (2) invoke automated tools that translate the language-based specifications into executable code, and (3) enable the customer to use the prototype executable code to refine formal requirements.
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