  We present a symbolic transition system and bisimulation equivalence for
psi-calculi, and show that it is fully abstract with respect to bisimulation
congruence in the non-symbolic semantics.
  A psi-calculus is an extension of the pi-calculus with nominal data types for
data structures and for logical assertions representing facts about data. These
can be transmitted between processes and their names can be statically scoped
using the standard pi-calculus mechanism to allow for scope migrations.
Psi-calculi can be more general than other proposed extensions of the
pi-calculus such as the applied pi-calculus, the spi-calculus, the fusion
calculus, or the concurrent constraint pi-calculus.
  Symbolic semantics are necessary for an efficient implementation of the
calculus in automated tools exploring state spaces, and the full abstraction
property means the semantics of a process does not change from the original.
