Sommerville-Software-Engineering-10ed

19.3 ■ System procurement 567
3. External competition If a business needs to compete more effectively or maintain
a competitive position, managers may decide to buy new systems to improve business
efficiency or effectiveness. For military systems, the need to improve capability
in the face of new threats is an important reason for procuring new systems.
4. Business reorganization Businesses and other organizations frequently restructure
with the intention of improving efficiency and/or customer service. Reorganizations
lead to changes in business processes that require new systems support.
5. Available budget The budget that is available is an obvious factor in determining
the scope of new systems that can be procured.
In addition, new government systems are often procured to reflect political
changes and political policies. For example, politicians may decide to buy new surveillance
systems, which they claim will counter terrorism. Buying such systems
shows voters that they are taking action.
Large complex systems are usually engineered using a mixture of off-the-shelf
and specially built components. They are often integrated with existing legacy systems
and organizational databases. When legacy systems and off-the-shelf systems
are used, new custom software may be needed to integrate these components. The
new software manages the component interfaces so that these components can interoperate.
The need to develop this “glueware” is one reason why the savings from
using off-the-shelf components are sometimes not as great as anticipated.
Three types of systems or system components may have to be procured:
1. Off-the-shelf applications that may be used without change and that need only
minimal configuration for use.
2. Configurable application or ERP systems that have to be modified or adapted
for use either by modifying the code or by using inbuilt configuration features,
such as process definitions and rules.
3. Custom systems that have to be specially designed and implemented for use.
Each of these components tends to follow a different procurement process. Figure 19.9
illustrates the main features of the procurement process for these types of system. Key
issues that affect procurement processes are:
1. Organizations often have an approved and recommended set of application software
that has been checked by the IT department. It is usually possible to buy or
acquire open-source software from this set directly without the need for detailed
justification. For example, in the iLearn system, we recommended that
Wordpress should be made available for student and staff blogs. If microphones
are needed, off-the-shelf hardware can be bought. There are no detailed requirements,
and the users adapt to the features of the chosen application.
2. Off-the-shelf components do not usually match requirements exactly, unless the
requirements have been written with these components in mind. Therefore, choosing