VMS Help SCA, SCA Topics, Glossary, relationship  *Conan The Librarian (sorry for the slow response - running on an old VAX)

    An association between two different occurrences. For example, the
    CALLED_BY relationship in SCA associates a primary declaration of
    a procedure with call references to other procedures and functions
    in that procedure. A relationship has both a source and a target.
    A relationship also has a relationship type. Relationships go in
    both directions. For example, the CALLED_BY relationship is the
    inverse of the CALLING relationship.