The LSST middleware design is based on a set of software abstractions; which provide standard interfaces for common communications services. The observatory requires communication between many subsystems, and comprehensive archiving of subsystem status data. Control commands as well as health and status data from across the observatory must be stored to support both the science data analysis, and trending analysis for the early detection of hardware anomalies.
The Service Abstraction Layer (SAL) is implemented using open source packages that implement open standards of DDS (Data DistributionService) for data communication and SQL for storage.
Designs for the automatic generation of code, documentation, and subsystem simulation, are being developed. Abstractions for the Telemetry datastreams, each with customized data structures, Command/Response, and the Logging and Alert messages are described.