The term composability is most often used in conjunction with object-oriented software development. In this respect, composability is defined as "the ability to rapidly create or adapt powerful systems to respond quickly to new hardware and software capabilities, dynamically respond to mission requirements, system health/integrity, operating environment, and possibly reconfigure during execution, for example, to trade fault tolerance or security for performance". [1]

In contrast, the modeling and simulation (M&S) community views composability as an element in the process to achieve automated scenario and exercise generation. In the eyes of the M&S community, composability allows a simulation system user complete flexibility to cross M&S domains or to configure a system "on the fly" from models or pieces of a model.

This paper is written with the express purpose of bounding the concept of composability in modeling and simulation, both what it is and why it is desired. Design requirements are defined, as well as challenges to the process. The paper concludes with a discussion regarding composability limitations within modeling and simulation.