?? theory of symmetric bimorphism vs of "nondegenerate" such ... ??? .... cups and caps vs bit about partition into pairs on image complement ... ??? .... ?? did baez really omit nondegeneracy condition in "composition alg" bit ?? ... ??? ...

?? morphism being injective map between family of t-structured set, vs morphism being map with t-structure on image complement ..... ???? .....