This article presents a practical approach to the design of federate architectures for the simulation developers by applying a well-known architectural style, layered architecture, from a developer's perspective. Adopting layered architecture for an HLA-based simulation (i.e. a federate) provides a clear separation to the following concerns; the user interface (where the user can be a human or an external system such as a GIS server), the simulation logic, and the HLA-specific communication. Thus, layered simulation architecture allows the simulation developers to focus on each concern separately and gives them the freedom to implement each layer in a different programming language, and to encapsulate the repetitive and low-level implementation details of the HLA federate interface specification. Moreover, the article introduces a wrapper for the current HLA runtime infrastructure, and gives an account of the suggested implementation practices through a case study. (c) 2012 Elsevier B.V. All rights reserved.