True concurrency

When modelling concurrency theory we often model the various things that can happen as interleaved. That is: given any two "events" a and b that have occurred, it must be that either a occured first or b occurred first. Models with true concurrency reject this notion of interleaving. Instead, they accept that events might truly happen at the same time.

In terms of CCS notation, the process a \mid b, which performs a and b in parallel, is not seen as equivalent to the process a.b + b.a, which nondeterministically chooses to perform a first then b, or the other way around.

Synonyms

Other names for true concurrency include:

• casual models
• casual-dependence models
• independence mdoels
• non-interleaving models
• partial-order models

Models of true concurrency

Examples of models of true concurrency include:

• Event structures
• Petri nets
• Mazurkiewicz trace languages
• Transition systems with independence
• Multiset rewriting