As simulation users adopted the High Level Architecture (HLA) to promote interoperability, composability, and reuseability, Federation Object Model (FOM) development and use necessarily grew apace. HLA federations have in many cases delivered on these promised "ilities" yet a simulation fortunate enough to be a member of multiple federations often does not realize these same benefits. Membership in multiple federations requires that the individual federate interoperate with multiple FOMs. This in turn usually equates to the federate developing multiple interfaces with limited opportunity for reuse. The Modeling and Simulation (M&S) Community has recognized this issue and sought its redress through composable object model approaches such as the Base Object Model (BOM) technology. This paper reports on work accomplished under the auspices of United States Joint Forces Command (USJFCOM) to decompose the FOMs used by the Joint Warfighting Center (JWFC), identify and eliminate redundant elements, and develop a composite Joint FOM. The effort is intended as a "proof-of-principle" on the basis of which USJFCOM might solicit broader community support in developing an object model library and process for composing FOMs for use by the Joint and Multinational M&S community.