Galois
Galois: A Language for Proofs Using Galois connections and ... - ALFA
Galois: A Language for Proofs Using Galois connections and ... - ALFA
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<strong>Galois</strong> connections<br />
Theoretical background<br />
<strong>Galois</strong> connections<br />
Definition (<strong>Galois</strong> connection)<br />
Given two preordered sets (A, ⊑ A ) and (B, ⊑ B ) and two functions<br />
B f<br />
A and g<br />
A B , the pair (f , g) is a <strong>Galois</strong> connection<br />
if and only if, for all a ∈ A and b ∈ B:<br />
f a ⊑ B b ⇔ a ⊑ A g b<br />
Graphical notation<br />
⊑ A<br />
A<br />
f<br />
g<br />
B<br />
⊑ B<br />
(f ,g)<br />
or (A, ⊑ A ) (B, ⊑ B )<br />
Paulo Silva (UMinho) <strong>Galois</strong> PLMMS’09 12 / 28