  Enabling preserving bisimilarity is a refinement of strong bisimilarity that
preserves safety as well as liveness properties. To define it properly,
labelled transition systems needed to be upgraded with a successor relation,
capturing concurrency between transitions enabled in the same state. We enrich
the well-known De Simone format to handle inductive definitions of this
successor relation. We then establish that ep-bisimilarity is a congruence for
the operators, as well as lean congruence for recursion, for all (enriched) De
Simone languages.
