This figure illustrates the connections between Software Elements, Software Frameworks, Software Institutes, and Reuse.
Figure 2. A tiered approach to software.
NSF's software vision views software reuse as a goal between within various types of projects, illustrated in Figure 2, from small software elements to larger software frameworks, which may make use of software elements, to software institutes, which may work with multiple software frameworks and elements.
This figure appears in NSF12113 - A Vision and Strategy for Software for Science, Engineering, and Education