A Few Things to Remember About Components
According to the UML User Guide, there are a number of things to remember when modeling the components of your system:
A component is a physical thing, not a logical or conceptual thing.
A component is replaceable -- it is possible to replace it with another that conforms to the same interfaces.
A component is part of a system -- it rarely stands alone.
A component conforms to and provides realization of a set of interfaces .