Concept models built by the Magic Concept Modeler satisfy the open-world assumption, that is, no one has complete knowledge of a system and a statement may be true irrespective of whether or not it is known to be true. This is the opposite of the closed-world assumption, which asserts that a statement is true only if it is known to be true and that knowledge of a system is known to be complete. A data model "subsetted" from a concept model would satisfy the closed-world assumption.