Concepts: Software Integration
The term "integration" refers to a software development activity in
which separate software components are combined into a whole. Integration is
done at several levels and stages of the implementation:
- Integrating the work of a team working in the same implementation
subsystem before releasing the subsystem to system integrators.
- Integrating subsystems into a complete system.
The Rational Unified Process approach to integration is to incrementally
integrate the software. Incremental integration means that
code is written and tested in small pieces, and then combined into a working
whole by adding one piece at a time.
The contrasting approach to incremental integration is phased
integration. Phased integration relies on integrating multiple (new and
changed) components at a time. The major drawback of phased integration is that
it introduces multiple variables and makes it harder to locate errors. This is primarily
due to the fact that an error could be in any one of the new
components, in the interaction between the new components at the core of the
system, or in the interaction between the new components.
The benefits of incremental
integration are:
- Faults are easy to locate. When a new problem occurs during incremental
integration, the new or changed component, or its interaction with the
previously integrated components, are the obvious places to look for a fault.
Incremental integration also makes it more likely that defects are
discovered one-at-a-time, which makes it easier to identify faults.
- The components are tested more fully. Components are integrated as they
are developed and then tested. This means that the components are exercised
more often than if integration is done in one step.
- Something is running earlier. Developers see early results from their
work instead of waiting for everything until the end, which is better for
their morale. It also makes getting early feedback possible.
It's important to understand that integration occurs at least once within
each and every iteration. An iteration plan defines what use cases to
design and what classes to implement. The focus of the integration
strategy is to determine the order in which classes are implemented and
combined.
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