A1	Concepts are not represented by a set of instances. Instead, a concept is assumed to exist in a state. A Hilbert space $\mathcal{H}$ is introduced, and a unit vector |ψ〉 ∈ $\mathcal{H}$ represents the state of the concept.
A2	Semantic estimations are not functions over the set of instances. Instead, a semantic estimation is a measurement operator, M : $\mathcal{H}$→$\mathcal{H}$, that projects onto a subspace of $\mathcal{H}$.