@prefix : <#> .
@prefix fam: <http://691.finin.org/o/family#> .
@prefix foaf: <http://xmlns.com/foaf/0.1/> .
@prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#> .

fam:mother_of 
    rdfs:domain foaf:Person;
    rdfs:range foaf:Person.

:eve fam:mother_of :cain.