There are a variety of approaches to implement the concept of reuse, including systematic and ad hoc reuse.
What distinguishes systematic reuse from other methods is the avoidance of multiple versions of otherwise
common elements. For example, suppose a reuse approach results in multiple instantiations of a common
element. If the instantiations are modified by software developers, then the element is no longer common
and can no longer be maintained as a single element. In the context of this standard, systematic reuse
excludes such approaches.