Information Technology Reference
In-Depth Information
Since most changes increase cost and project length, senior developers should
evaluate them closely before approving them. Before any changes are approved,
the impact on deliverables needs to be documented, e.g. documentation, cost,
deadlines and current work assignments (Thayer and Dorman
1990
) (Fig.
13.6
).
13.3 Phase III: Object Oriented System Design
System design is the critical step between specification and implementation. It is
here that a project is either made or broken. Specification is the development
process of designing classes, objects, data stores, user interfaces and many other
important project aspects. The first step to designing a good working system is a
Stakeholders and Interests List. This list is extremely important and should not be
pushed aside for what may seem like more pressing issues.
The following is a brief outline of what is required in a specification document.
The main parts of the document are an understanding of the stakeholder's needs,
the system interface and the system composition. There are many more kinds of
documents and diagrams that can be used to supplement and complement the
following, but the following sections are absolutely necessary. Each section will
provide a brief explanation and an example of what is expected to be contained in
each portion of the specification.
13.3.1 Stake Holders and Interests List
The first step to this list will be to determine the stakeholders. A simple example
would be a point of sale system or POS. In this scenario we can document at least
two stakeholders quickly, the first being the cashier physically moving the product
in exchange for currency. The second stakeholder is the salesperson. The sales-
person will have sold a good or service and directed a customer to a cashier to
handle the actual transaction. From this rudimentary knowledge, a stakeholders
and interests list can be started such as the one in Fig.
13.7
.
13.3.2 Use Case
All good software has a particular use in mind when it is being developed. This use
is described in a use case. A use case expands on the stakeholders and interests list
and presents, typical and atypical interactions of the stakeholders with the system
in questions. Use cases are broken into three separate scales. The first is a brief
overview. In this scenario the system and actors are roughly discussed and an
outline format is used to document the flow of interaction. Most often, alternate
