  CSPe is a specification language for runtime monitors that can directly
express concurrency in a bottom-up manner that composes the system from
simpler, interacting components. It includes constructs to explicitly flag
failures to the monitor, which unlike deadlocks and livelocks in conventional
process algebras, propagate globally and aborts the whole system's execution.
Although CSPe has a trace semantics along with an implementation demonstrating
acceptable performance, it lacks an operational semantics. An operational
semantics is not only more accessible than trace semantics but also
indispensable for ensuring the correctness of the implementation. Furthermore,
a process algebra like CSPe admits multiple denotational semantics appropriate
for different purposes, and an operational semantics is the basis for
justifying such semantics' integrity and relevance. In this paper, we develop
an SOS-style operational semantics for CSPe, which properly accounts for
explicit failures and will serve as a basis for further study of its
properties, its optimization, and its use in runtime verification.
