The component diagram illustrates the software
components that will be used to build the system. These may be
built up from the class model and written from scratch for the new
system, or may be brought in from other projects and 3rd party
vendors.
Components are high-level aggregations of smaller
software pieces, and provide a 'black box' building block approach
to software construction. A component can always be considered an
autonomous unit within a system or subsystem. It has one or more
provided and required interfaces (potentially exposed via ports),
and its internals are hidden and inaccessible other than as
provided by its interfaces. Although it may be dependent on other
elements in terms of interfaces that are required, a component is
encapsulated and its dependencies are designed such that it can be
treated as independently as possible. As a result, components and
subsystems can be flexibly reused and replaced by connecting
(“wiring”) them together via their provided and
required interfaces.
The component diagram shows the relationship
between software components, their dependencies, communication,
location and other conditions. Component diagrams are used to
structure components in software systems. They examine and manage
dependencies between components or interfaces of components. A
component represents a modular, deployable, and replaceable part of
a system.
One or more classifiers that reside on the
component typically specify a component. Subsets of these
classifiers explicitly define the component's external interfaces.
A component conforms to the interfaces that it exposes, where the
interfaces represent services provided by elements that reside on
the component.
Example:
