Read First: Relation A tuple gives a set of things that participate in a relation between those things. For example, to put Jane and John in the marriage relation, you create a tuple of Jane and John, (Jane, John) and classify it by the Marriage relation. Usually the elements of a tuple are ordered in a certain way to identify the places, but tuples may be implemented in any manner. The only requirement is that there is a way to find an element in the tuple given the place of that element. For example given the tuple expressing the marriage of Jane and John, there should be a way to find the Jane when asked for the element filling the Wife place. We could not think of a case where an object is both a tuple and an object type, but we also could not prove that one doesn't exist. So we have left Tuple non-disjoint from Object Type, and consequently, TupleClassifier non-disjoint from Metaobject Type. Tool that provide an object that is both and tuple and an object type will need to define a semantics for the instances of tuple. We would be interested in hearing about such a semantics. See comments at Place Relation.