2. w : World
3.
i,x:Id. vartype(i;x) 
r M(i).ds(x)
4.
i:Id, a:Action(i). 
isnull(a) 
(valtype(i;a) r M(i).da(kind(a)))
5.
l:IdLnk, tg:Id. (w.M(l,tg)) r M(source(l)).da(rcv(l; tg))
6.
i,x:Id. M(i).init(x,s(i;0).x)
7. i : Id
8. t :
9.
isnull(a(i;t))
10. IdLnk
11. m(i;t) = m(i;t)
12. {m:Msg(w.M)| source(mlnk(m)) = i } List
13. {m:Msg(w.M)| source(mlnk(m)) = i } List
14. u : {m:Msg(w.M)| source(mlnk(m)) = i }
u 
Msg
