Design of in idiptition strategy

The steps in this part of the adaptation planning process are outlined in Figure C.9. Having identified the potential risks in the adaptation, counter-measures can now be contemplated. EM prov ides some guidelines as to the kind of measures to be used against certain types of threat, although there is no claim that the adv ice by any means exhausts this subject.

With the example of producing German language user documentation, a risk was identified that the base system could change. This could be interpreted as an example of the generic risk 'evolving requirements'. EM suggests as possible counter-measures the implementation of a stringent change control procedure to discourage unnecessary changes, and measures to make sure that delivered products arc easy to change. The latter suggestion could be implemented by. for example, having supporting documentation that cross-referenced the user documentation to the system specification so that the effect of changes in the base system could be quickly traced through to user documentation. The user documentation might also be structured to make use of appendixes for details such as error messages, which are likely to change.

Figure C.9 Design of on adaptation strategy.

The risks lo an adaptation can also he dealt with at a higher level by considering the overall approach to the adaptation project. This will influence:

• the description approach;

• the construction approach;

• the installation approach.

The description approach is concerned w ith the method to be used to describe the systems involved. This is divided by EM into a cognitive approach and a social approach.

One of the two alternative cognitive modes is analytical where information about the system is abstracted into simplified views that focus on certain aspects of the system to the exclusion of others. For example, in SSADM, the Logical Data Structure (I DS) is an abstraction of the data needed by a system. On the other hand, the experimental mode, as its name implies, elicits information by using experiments to learn about the system. The use of prototypes is a central technique in this mode. The analytical and experimental modes arc not mutually exclusive.

The social approach is the w ay that the developers and users work together. T his can be either in an expert-driven or a participatory mode. In the expert-driven mode, systems analysts, or the equivalent, w ill fact-find among the users and then go away and. on their own. produce the system description. In the participator) mode, the descriptions are produced in a joint effort betw een developers and users - Joint Applications Development exemplifies this approach.

Each of the cognitive approaches can he used in conjunction with either of the social approaches.

In common with ISO 12207. EM offers advice on whether a one-shot, incremental, or evolutionary approach would he hest. The distinctive feature of EM is that it distinguishes between construction and installation. It allows, for example, for a system to he built in increments but to be installed in one shot - or vice versa.

As well as the one-shot, incremental and evolutionary options in relation to construction and installation, EM provides guidance* on whether, geographically, installation should be carried out in all locations in one step, or in stages where groups of locations are dealt with in turn.

The general heuristics provided by EM about the most suitable approach to description, construction and installation are shown in Table C.I and Table C.2.

Table C. I General heuristics of suitability of installation/construction approaches

Situational factor

Installation/construction approach

Schedules

Complexity Uncertainty

one-shot

incremental evolutionary

normal

simple certain uncertain

complex certain

uncertain

tight simple certain unccnain tight simple certain unccnain complex certain uncertain

Heuristic' is defined as furthering investigation but otherwise unproved or unjustified" in the Longman Concise English Dictionary

Table C.2 General heuristics on the suitability of description

Expert-driven

Participatory

Analytical

Situation is complex but information/business processes are relatively straight-forward

Information/business processes are relatively complex

Experimental

Situation is uncertain but participatory approach unsuitable

Situation is uncertain but personnel are experienced and time-scales are adequate

EM suggests that these options be considered in the following order:

1. installation - system coverage (that is. one-shot, incremental, evolutionary);

2. installation - geographical coverage;

3. construction;

4. description.

These 'first-cut' strategy options might be revised in the light of the more detailed heuristics that are prov ided by HM. For example, although the general heuristic guidance might point to an analytical/expert -driven approach, because of the importance of winning and maintaining the support of the users for the new system, you might decide to plump for a more participatory approach.

While the adoption of a particular approach to the adaptation could have reduced some risks, it is possible that it can generate completely new ones - the impact of the strategy has to be scrutinized to remove this possibility.

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