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Specification of Reactive Hardware/Software Systems - Electronic ...

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10.4 A System <strong>of</strong> Basic Transformations 311<br />

Transformation<br />

<br />

2<br />

e BSpec ¢ 1 BSpece 2 ¥ envs1 ¥ envs2 Sysp Sys ¥<br />

A<br />

B<br />

<br />

¢<br />

Transformation 3<br />

e BSpec1 (BSpece 2 ¢ BSpece ¥ 3)¥ envs1 envs2 envs3 Sysp Sys ¥<br />

c<br />

a<br />

a<br />

b<br />

d<br />

¢<br />

¡<br />

¢<br />

¡<br />

a<br />

A<br />

B<br />

c<br />

b<br />

d<br />

<br />

e BSpec ¢ 2 BSpece 1 ¥ envs2 ¥ envs1 Sysp Sys ¥<br />

¨<br />

¡<br />

¢<br />

<br />

e (BSpec ¢ 1 BSpece ¢ 2) BSpece 3 ¥ envs1 envs2 ¥ envs3 Sysp Sys ¨<br />

¥<br />

According to 2 and 3 the parallel composition operator is commutative and associative.<br />

This gives us the liberty to write BSpece 1 ¢ BSpece2 ¢ BSpece3 ¢ BSpece4 in stead <strong>of</strong><br />

for example BSpece 3 ¢ ((BSpece1 ¢ BSpece ¢ 2) BSpece 4) without raising any confusion. In the<br />

sequel we freely make use <strong>of</strong> this liberty.<br />

Transformation 4<br />

e<br />

<br />

BSpec ¥ envs¥ p f ¥ Sys<br />

§ Sys<br />

<br />

e BSpec § f<br />

¢<br />

¥ envs¥ Sys ¡ ¡<br />

p ¥ Sys<br />

¤ if f ChSort(BSpece ¥ Sysp ) ¡ ¤ = f ChSort(BSpece ¥ Sysp ¨<br />

)<br />

Here f ¤ D is the restriction <strong>of</strong> channel renaming f to domain D. 4 states that channel<br />

renaming function f may be replaced by f ¡ if both functions perform a similar renaming<br />

<strong>of</strong> the actual involved (observable) channels.<br />

Transformation 5<br />

e<br />

§ BSpec § f ¡ ¥ envs¥ f Sysp Sys ¥<br />

<br />

e BSpec § f ¥ f<br />

¢<br />

¥ envs¥ Sys ¡ ¡<br />

p ¨<br />

¥ Sys<br />

By Transformation 5 two successive channel renaming functions can be reduced to a<br />

single one and vice ¥ versa. ¡ f f is the composition <strong>of</strong> functions f ¡ and f , ¥ i.e. ¡ (f f )(ch) =<br />

f (f (ch)) for each channel ¡ ch.<br />

Transformation<br />

<br />

6<br />

e (BSpec ¢ 1 BSpece f ¥ envs1 envs2 ¥ Sys 2)§ p Sys ¥<br />

<br />

e BSpec § 1 ¢ f BSpece 2 § f ¥ envs1 ¥ envs2 Sysp Sys ¥<br />

if NoComChange(BSpece 1 ¥ BSpece 2 ¥ envs1 envs2 ¥ Sys ¥ p Sys¥ f ) ¨<br />

¥<br />

¢<br />

¡

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