Description: Define the class of
converse reflexive relations. This is practically
dfcnvrefrels2 38484 (which uses the traditional subclass
relation ⊆) :
we use converse subset relation (brcnvssr 38462) here to ensure the
comparability to the definitions of the classes of all reflexive
(df-ref 23534), symmetric (df-syms 38498) and transitive (df-trs 38528) sets.
We use this concept to define functions (df-funsALTV 38637, df-funALTV 38638)
and disjoints (df-disjs 38660, df-disjALTV 38661).
For sets, being an element of the class of converse reflexive relations is
equivalent to satisfying the converse reflexive relation predicate, see
elcnvrefrelsrel 38492. Alternate definitions are dfcnvrefrels2 38484 and
dfcnvrefrels3 38485. (Contributed by Peter Mazsa,
7-Jul-2019.) |