APECS: An AADL and polychrony based embedded computing system design environment with an elevator control case study

Architecture Analysis and Design Language (AADL) is a standard that originated in the avionics domain, but is now being used in avionics and other critical distributed real-time embedded system design. AADL provides a formal notation and semantics for capturing an entire distributed platform architecture (hardware components, protocols, and software architecture annotated with properties including real-time measures). The software architecture captures the location and structure of processes, threads, and the data and control flow specifications. The behavior of the processes/threads/subprograms are provided via a native state machine language or via a behavioral annex. Schedulability, performance, and other system level properties can be analyzed using various tools. Even code synthesis - targeting the formally described platform components and middleware can be enabled if the threads/processes can be behaviorally specified. In this paper, we describe our methodology and a design environment both named APECS. APECS is meant for enabling an end-to-end distributed real-time embedded system design which integrates a number of existing tools, and our own polychronous language based specification language MRICDF, and the corresponding synthesis methodology. While the environment is in an advanced stage of development, we illustrate the architecture of the design environment, and illustrate the methodology through a non-trivial case study. The case study uses APECS methodology and tools in developing the distributed control for a 4 bank elevator system in a 5 story building. We posit this paper as a methodology and tool paper and it is written in a tutorial spirit rather than a paper describing new theories or algorithms.