... T1/σ1 and T /σ −→ T 2 /σ 2 , there exist two further executions T1/σ1−→T1/σ1 and T 2 /σ 2 −→ T 2 /σ 2 such that the configurations T1/σ1 and T 2 /σ 2 areequivalent with ... Forexample, take β ≡ x=y and σ ≡ x=f(x1x 2 )∧y=f (y1y 2 )∧x 2 =a∧y 2 =b.ThetellCopyrightc 20 0 1-3 by P. Van Roy and S. Haridi. All rights reserved.806 Language Semantics13 .2 Declarative concurrencyIn ... S{X1→x1, ,Xn→xn} stands for the simultaneous substitu-tion of the free occurrences of X1by x1, X 2 by x 2 , , Xnby xn. For instance,the substitution of Foo by x and Bar by y in the...