Interoperability and reusability are major issues in large-scale software system development. Military applications, one of such large scale software systems, have utilized the Common Operating Environment (COE) for the last decade. The COE reduces duplicated development effort and enhances the reusability/interoperability by providing standardized infrastructure and development guidelines. The COE is an intrinsically distributed computing environment, and needs a various techniques in realization. Generally, widely accepted techniques in industry and academic are practical for such environment to implement. We performed a development of the COE pilot project, and in this paper we cover some issues on the COE realization and show certain ways for practical implementation.