:: deftheorem Def3 defines compatible ALGSTR_4:def 3 :
for M being multMagma
for R being Equivalence_Relation of M holds
( R is compatible iff for v, v9, w, w9 being Element of M st v in Class (R,v9) & w in Class (R,w9) holds
v * w in Class (R,(v9 * w9)) );