Software Engineering for Students A Programming Approach

342 Chapter 27 ■ The unified process
The inception phase
The goal of this phase is to understand the scope of the project, build a business case
and obtain stakeholder agreement.
Understanding the scope involves interviewing the client and recording their requirements.
The functional requirements are recorded as use cases and we saw in Chapter 4
on requirements how to accomplish this activity for the ATM system.
Building a business case means carrying out a calculation of the financial costs and
benefits, which was outlined (for the ATM) in Chapter 3 on the feasibility study. This
calculation reveals that the system is hugely cost effective.
Obtaining stakeholder agreement means checking with the identified groups that
they are happy and committed to the project. In the case of the ATM, the stakeholders
may include the client, the bank workers, the bank’s customers, the senior management
of the bank, the bank IT department and relevant public authorities. Let us assume that
these various groups are happy for the project to go ahead.
The elaboration phase
This involves completing the statement of requirements, devising the general architecture
of the system, identifying and assessing the major risks and drawing up and agreeing
a plan for the development.
For the ATM, the user functions can be established and documented as use cases.
For the ATM, a decision about the division of labor between ATM software and
server software needs to be made. The protocol for the communication between ATMs
and server needs establishing. Then the architecture is checked by constructing a working
skeletal system.
Now that the requirements are well established and the architecture is trustworthy,
there is greater certainty in the project. However, an assessment is made of any risks to
the project and plans made accordingly.
Now, a detailed plan for the remainder of the project can be drawn up.
The construction phase
This phase constitutes the actual construction of the software.
This consists of four iterations. The first is an implementation of the user interface
(with no functionality). This establishes that the design of the user interface is acceptable.
It also confirms that it will provide the desired functionality.
The second iteration is a program to interface with the database on the server, in
order to ascertain that a satisfactory connection can be made, providing the functionality
required by the ATM application.
The next iteration is a full implementation of the system, but using only a single
ATM. This establishes that the system is technically feasible for a single user.
Finally a multi-user system is constructed.
This account of the four iterations assumes that all goes well. In practice, the assessment
at the end of an iteration might reveal that there is a problem. This would need to
be solved by such measures as rescheduling the project or using an alternate technology.