PALM will provide a MPMD implementation of a data assimilation system, in which every component is an independent autonomous code.

The physics of the problem are dealt with inside the components, whilst PALM performs the algebra and provides synchronisation and communication. PALM will provide the interfaces between the components and the overall structure.

The size of the problem and the operational purposes of a forecast system make the performances a key-point of the project.

Key words: Data Assimilation, MPMD programming, Parallel Computing, Message Passing, Process Management