Distributed Discrete Event (DDE) Domain

The Distributed Discrete Event (DDE) domain incorporates a distributed notion of time into a dataflow style communication semantic. Much of the functionality of the DDE domain is consistent with the Process Networks domain. In particular, this model of computation's mechanism for dealing with blocking due to empty or full queues is functionally identical to that of the PN domain.

The DDE domain's use of time serves as the point of divergence in the respective designs of DDE and PN. Time progress is communicated between actors by passing tokens that have time stamps associated with them. In a network of DDE actors each actor has a local notion of time. To facilitate this local notion of time, actors in a DDE model adhere to the following constraints.

Successive tokens emitted from any actor's output port must have a time stamp that is greater than or equal to that of previous tokens.
An actor can consume a token on an input port (P1) only if the other input ports of that actor have pending tokens with time stamps greater than or equal to that of P1.
If an actor has two or more input ports with pending time stamps that are identical, then a local input port prioritization rule must be invoked to determine the ordering of these simultaneous tokens.

The above rules facilitate a local notion of time and are consistent with the conservative blocking mechanism of Chandy and Misra's distributed discrete event system.

We are approaching the DDE model of computation as the intersection between dataflow and discrete event semantics. This allows us to study DDE semantics from two different perspectives. In particular, we can benefit from denotational semantics that are based on metric spaces (the Banach oriented DE approach) or posets (the Tarskian oriented dataflow approach). Matthews offers a partial metric topology which incorporates both of these mathematical tools.

The DDE domain is an experimental domain, the code has not been reviewed, and the interfaces are likely to change.

Misra, Jayadev, "Distributed Discrete Event Simulation," ACM Computing Surveys, vol. 18, no. 1, March 1986, pp 39-65.
Fujimoto, Richard M., "Parallel Discrete Event Simulation," Communications of the ACM, vol. 33, no. 10, October 1990, pp 30-53.
Matthews, S. G., "Partial Metric Topology," General Topology and Applications, Proceedings of the 8th Summer Conference, Queen's College (1992), Annals of the New York Academy of Science, vol. 728, pp 183-197.