Some definitions of interest.
Knd	Def Knd == (IdLnkId)+Id
	Thm* Knd  Type
Id	Def Id == Atom
	Thm* Id  Type
has-src	Def has-src(i;k) == isrcv(k)source(lnk(k)) = i
assert	Def b == if b True else False fi
	Thm* b:. b  Prop
isrcv	Def isrcv(k) == isl(k)
	Thm* k:Knd. isrcv(k)
lnk	Def lnk(k) == 1of(outl(k))
	Thm* k:Knd. isrcv(k)  lnk(k)  IdLnk
lsrc	Def source(l) == 1of(l)
	Thm* l:IdLnk. source(l)  Id

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