T:Type, eq:EqDecider(T), es:event_system{i:l}, x:Id, e:{e:es-E(es)| es-dtype(es; loc(e); x; T)} .
change-to(x;e)  (?es-E(es)) 

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Definitions	A c B, x. t(x), P  Q, P  Q, prop{i:l}, P  Q, P  Q, P  Q, t.1, es-dtype(es; i; x; T), EqDecider(T), change-to(x;e), t  T, x:A. B(x), x:A. B(x), x(s), e<e'.P(e)
Lemmas	it wf, unit wf, alle-le wf, es-first wf, not wf, alle-between3 wf, es-when wf, es-change-to wf, existse-before wf, es-vartype wf, es-isconst wf, assert wf, iff wf, bool wf, deq wf, event system wf, Id wf, es-loc wf, es-dtype wf, es-E wf