Authorization in a distributed system using access control lists and groups

In a method of controlling sharing of an object between entities in a distributed system, a processor will identify an object and generate an access control list (ACL) for the object so that the ACL includes a list of clauses. Each clause will include a blessing pattern that will match one or more blessings, and at least one of the clauses also may include a reference to one or more groups. Each group represents a set of strings that represent blessing patterns or fragments of blessing patterns. The processor may generate each clause of the ACL as either a permit clause or a deny clause to indicate whether an entity or entities that have a blessing matched by the blessing pattern are permitted to access the object. The processor will save the ACL to a data store for use in responding to a request to access the object.