CS 641 meeting -*- Outline -*- * the semantic homomorphisms (4.8) We'd like to know that wp.c and wlp.c are homomorphisms. To do this we show that any language extentsion is a hom. Recall that MP is set of positively conjunctive predicate transformers Thm: if v \in A -> MP, then v(.) \in A(.) -> MP is a homomorphism. Q: What does it mean for w \in A(.) -> MP to be a hom? (all q,r \in A(.) :: w.(q;r) = w.q o w.r) (all C : {} \neq C \subseteq A(.) : w.([] c \in C :: c) = (inf c \in C :: w.c)) Q: Can you prove this? straightforward calculation. Corollary: (a) for every v \in (H -> MU), function v^1 is a hom in (A(.) -> MU). So wlp is a hom in (A(.) -> MU). (b) for every v \in WT, function v^0 is a hom in A(.) -> MP. So wp is a hom in (A(.) -> MP).