FUNCTION acyclic_document_relationship
(relation : document_relationship, relatives : SET [1:?] OF document, specific_relation : STRING) : BOOLEAN;
LOCAL
x : SET OF document_relationship;
END_LOCAL;
IF relation.relating_document IN relatives THEN
RETURN (FALSE);
END_IF;
x := QUERY(doc <* bag_to_set(USEDIN(relation.relating_document, 'DOCUMENT_SCHEMA.' + 'DOCUMENT_RELATIONSHIP.' + 'RELATED_DOCUMENT')) | specific_relation IN TYPEOF(doc));
REPEAT i := 1 TO HIINDEX(x);
IF NOT acyclic_document_relationship(x[i], relatives + relation.relating_document, specific_relation) THEN
RETURN (FALSE);
END_IF;
END_REPEAT;
RETURN (TRUE); END_FUNCTION; -- acyclic_document_relationship
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