A KB dependent collection of collections of collections (and thus an instance of type of collection type and a specialization of type of collection). A sibling-disjoint collection type is such that its known (i.e. KB-represented) instances are collections that -- save for any that are related to each other by generalization and any that are explicitly asserted to be exceptions (see Sibling Disjoint Exceptions) -- are disjoint from each other.

More precisely, each instance SIB of sibling disjoint collection type is a collection of collections that has the following KB-dependent property:

For any two known instances COL1 and COL2 of SIB, at least one of the following is known to hold:

  (a) (generalization COL1 COL2)
  (b) (generalization COL2 COL1)
  (c) (Sibling Disjoint Exceptions COL1 COL2)
  (d) (Disjoint With COL1 COL2)

Moreover, note that if MT is a context (see context) in which (i) both (Isa COL1 SIB) and (Isa COL2 SIB) hold and (ii) neither (generalization COL1 COL2) nor (generalization COL2 COL1) nor (Sibling Disjoint Exceptions COL1 COL2) is known to hold (see Known Sentence), then (Disjoint With COL1 COL2) holds by default in MT.

For example, in Cyc's knowledge about biology both person and dog are instances of the sibling-disjoint collection type species, while neither (generalization person dog) nor (generalization dog person) nor (Sibling Disjoint Exceptions person dog) is known to hold in that context; consequently, (Disjoint With person dog) holds by default in Cyc's knowledge about biology. Instances of sibling disjoint collection type include taxonomic group (and its specializations), type of organism part, and type of relationship classified by arity.

See the generalization sibling disjoint set or collection type. Also cf. the stronger notion of disjoint classification scheme.