Guarded series-parallel strings generalize guarded strings, giving a language model for concurrent Kleene algebra with tests.
The guarded series-parallel string model satisfies the weak exchange law.
We define a simpler type of branching automata proving that the fork-regular and series-rational languages coincide.
We define concurrent deterministic flowchart schemes and relate them to concurrent Kleene algebras with tests.
A purely relational CKAT model is defined based on binary relations over a positive separation algebra.