| Definitions | fifo-antecedent(es;Sys;f), P     Q, input-forwarding{i:l}(es; Cmd; Sys; isupdate; In; f),  x:A. B(x), x:A  B(x), {x:A| B(x)} , P   Q, type List, chain-config(es;Sys;chain), p-conditional(f; g), chain-consistent(f;chain), adjacent(T;L;x;y), Id, loc(e),  b, E, P & Q, P    Q,  A, is-query(In;isupdate;e), es-interface-history(es; X; e),  x:A. B(x), E(X), s = t,  , if b then t else f fi , e    X, ||as||, filter(P;l), X(e), f(a) |