Other ways of categorizing prototypes

What is being learnt?

The most important reason for having a prototype is that there is a need to learn about an area of uncertainty. For any prototype it is essential that the project managers define at the outset what it is intended to learn from the prototype.

This has a particular relevance to student projects. Students often realize that the software that they are to write as part of their project could not safely be used by real users. They therefore call the software a 'prototype'. However, if it is a real prototype then they must:

• specify what they hope to learn from the prototype;

• plan how the prototype is to be evaluated;

• report on what has actually been learnt.

Prototypes may be used to find out how a new development technique can be used. This would be the case where a new methodology is being used in a pilot scheme. Alternatively, the development methods might be well-known, but the nature of the application might be uncertain.

Different projects will have uncertainties at different stages. Prototypes can therefore be used at different stages. A prototype might be used, for instance, at the requirements gathering stage to pin down requirements that seem blurred and shifting. A prototype might, on the other hand, be used at the design stage to test out the users' ability to navigate through a sequence of input screens.

To what extent is the prototyping to be done?

It would be unusual for the whole of the application to be prototyped. The prototyping might take one of the following forms, which simulates only some aspects of the target application.

Mock-ups For example, copies of the screens that the system is to use are shown to the users on a terminal, but the screens cannot actually be used.

Simulated interaction For example, the user can type in a request to access a record and the system will respond by showing the details of a record, but the details shown are always the same and no access is made to a database.

Partial working model:

• vertical - some features are prototyped fully

• horizontal - all features are prototyped but not in detail (for example, there might not be a full validation of input).

What is being prototyped?

The human-computer interface With information systems, what the system is to do has usually been established and agreed by management at a fairly early stage in the development of the system. Prototyping tends to be confined to establishing the precise way in which the operators are to interact with the system. In this case, it is important that the physical vehicle for the prototype be as similar as possible to the operational system.

The functionality of the system In other cases, the precise way that the system should function internally will not be known. This will particularly be the case where a computer model of some real-world phenomenon is being developed. The algorithms used need to be repeatedly adjusted until they satisfactorily imitate the behaviour they should be modelling.

At what stage of a system development project (for example, feasibility study, Exercise 4.5 requirements analysis etc.) would a prototype be useful as a means of reducing the following uncertainties?

(a) There is a proposal that the senior managers of an insurance company have personal access to management information through an executive information system installed on personal computers located on their desks. Such a system would be costly to set up and there is some doubt about whether the managers would actually use the system.

(b) A computer system is to support sales office staff who take phone calls from members of the public enquiring about motor insurance and give quotations over the phone.

(c) The insurance company is considering implementing the telephone sales system using the system development features supplied by Microsoft Access. They are not sure, at the moment, that it can provide the kind of interface that would be needed and are also concerned about the possible response times of a system developed using Microsoft Access.

4.12 Tools

Special tools are not essential for prototyping but some have made it more practicable.

Application building tools have many features that allow simple computer-based information systems to be set up quickly so that they can be demonstrated to the staff who will use them. An application written in a 3GL becomes more and more complicated as changes accumulate in its code and this makes the software more difficult to alter safely, while applications implemented using application builders that are often form- and table-driven remain flexible.

It has been suggested that the ease of use of some 4GL application builders and the increasing IT awareness of end users might allow end users to create their own prototypes.

Chapter 9 explores Where a prototype is being constantly tested by the users and modified by the configuration developers there is a need to be able to control the different versions being management further. produced and where necessary to back-track to previous versions.

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  • Dorthy Hillard
    What are the ways of categorizing prototypes?
    3 years ago

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