The JOYCE+ model for multisite distributed systems is presented and the operational semantic of the asynchronous communication between processes is illustrated with Petri nets. The syntax of the JOYCE+ language is presented in terms of the Guarded Commands language. The expressive power of the JOYCE+ language in distributed synchronization problems with timeout handling is illustrated through examples. Software development environments (based on JOYCE+) for distributed systems over multi- and monoprocess computer networks are discussed.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
