[an error occurred while processing this directive]

Software Development Process

The description of process given here is intended to cover both complete software applications and their individual components. There are important aspects of application-level process that are not covered here. For example, iterative development is an important approach that allows development to proceed while permitting some changes in requirements. See [FS97] for a good presentation of the application-level process.

For experienced software developers, the component-level process is often less conspicuous, involving well-established and automated patterns of thinking. This does not diminish its importance. Software developers need good automated thinking habits to free their minds for dealing with more complex issues.

Phases of Software Development

Some of the activities in the software development process are sequential in nature, dividing the process into the following phases.

Requirements analysis - specifying the functional capabilities needed in the software. Use-cases are an important tool for communication about requirements between software developers and their clients.
Products: software requirements documents for the software
Objectives: capture the client's needs and wants
Domain analysis - developing concepts, terminology, and relationships essential to the client's model of the software and its behavior. Conceptual-level class diagrams and interaction diagrams are important tools of domain analysis.
Products: client-oriented model for the software and its components
Objectives: capture the client's knowledge framework
Client-oriented design - specifying components of the software that are visible to the client and the components' behavior in terms of their attributes, methods, and relationships to other components. Specification-level class diagrams and interaction diagrams are important tools of client-oriented design.
Products: client-oriented specifications for components
Objectives: define the structure of interactions with the client, providing methods that satisfy the client's needs and wants, operating within the client's knowledge framework
Implementation-oriented design - determining internal features and method algorithms for the software.
Products: implementation-oriented specifications for components
Objectives: define internal structure and algorithms for components that meet client-oriented specifications
Implementation - writing and compiling code for the individual software components.
Products: source code and binary code for software components and their test software
Objectives: produce coded components that accurately implement the implementation-oriented design
Integration - putting the software components into a context with each other and with client software.
Products:
Objectives: test the software components in the context in which they will be used
Packaging - bundling the software and its documentation into a deliverable form.
Products: software and documentation in an easily installed form
Objectives:

Ongoing Activities in Software Development

The following software development activities cannot be isolated to a single phase. They are repeated throughout the process.

Risk analysis - management activities that attempt to identify aspects of the development process that have a significant chance of failing. After risks are identified, managers have several options. One drastic possibility is cancellation of a project. More likely, risks indicate the need for a change in goals or a change in how resources are allocated.
Planning - management activities that determine the specific goals and allocate adequate resources for the various phases of development. Resources include time, work and meeting space, people, and developmental hardware and software. Risk analysis can be viewed as preparation for planning. For phases with high risk, managers may allocate more time or people, or they may allocate more skilled people, or they may devote time to the training of the people that are involved.
Verification - activities directed at ensuring that the products of the various phases of development meet their objectives. Testing is an important part of verification that takes place during implementation and integration. There are two kinds of testing: black-box and white box. Black-box testing is testing how software meets its client-oriented specifications, without regard to implementation. White-box testing uses knowledge of implementation to determine a testing plan that all paths of control have been exercised.
Verification is also important in early phases of software development. Reviews [FW90] are the primary methods of verification for the analysis and client-oriented specification phases. Analytic verification is an important tool for the implementation-oriented specification phase.
Documentation - providing instructions and information needed for the installation, use, and maintenance of software. Documentation for users is obviously important, but it is not the only kind of documentation. Because of the importance of maintenance, the documentation of components for use by other developers is also essential.

The Importance of a Disciplined Process

A disciplined process serves two main purposes: it helps the developers to better understand the what they are doing, and it helps managers to make more accurate predictions about how long a project will take. Predictatability is crucial for setting reasonable goals and planning resource allocation.

Understanding

As software developers work through a disciplined process, they are developing a complex mental roadmap of the values of the client, the concepts that are important to the client, software patterns for achieving the desired behavior, and implementation methods. Common sense and experience both support the importance of this understanding.

Common sense: Suppose that a software development process has been in progress for several months or years. One of the development team members has changed jobs so that a replacement is needed. Or, the project is behind schedule so management has allocated more people to work on the project. So you have been added to the team. Will you be as effective as the other team members? Not likely.
Experience: Brooks [Brooks95] has discussed management problems arising from adding people to a project that is behind schedule in order to catch up. Often, the result is that the project slips further behind schedule. The reason for this is the new people do not have a mental roadmap. In order to acquire it, experienced team members will have to dedicate some time to bringing them up to speed.
The fact that managers did not see the obvious should not be construed as proof that managers are stupid. Managers have to go through a similar process to learn how to manage effectively. A lot of facts are obvious, but that does not mean that you will see them when they are important. You do not see things that are obvious until you have had experiences that stress their importance. You also need to recognize that they are important.

Predictability

A disciplined process is also essential for management of resources so that managers can anticipate needs and coordinate between multiple projects. Software development firms will often impose a more stringent process than is needed to just get the job done. Part of the reason for this is that over time, the managers develop a better sense of how long it takes to accomplish various kinds of tasks and what kinds of skills are needed. Without a disciplined process, it is impossible to develop this sense - with an undisciplined process, there is just too much variation in how long it takes to accomplish a task, and the variation is usually in an undesirable direction.

[an error occurred while processing this directive]