PROCESS MODELS OF COMPUTATION
A process is a sequence of UCs where each external interaction implicitly marks the end of one UC and the beginning of another UC and cycles among are allowed.
A. Variants of non-atomic process model - the firing rules of each UC incompletely specify the conditions for a minimum schedule, therefore the occurrence of a fault may require cascading rollback.
1. Process/shared name space - a set of processes with a common shared name space. Interactions among processes is through shared name access dependency relations.
2. Process/message model - a set of processes with partitioned name spaces which interact via data dependency relations (messages).
2.1 synchronous message model - data dependency relations always occur in pairs with an output dependency external to the process from one uc always followed by a data dependency from an external source to the next uc in the process sequence. It is convenient to incorporate synchrony/asynchrony as an attribute of a single data dependency to allow for compact specification of this property.