By 'informational entropy', we understand an inherent boundary to knowability, due e.g. to perceptual, theoretical, evidential or linguistic limits. In this paper, we discuss a logical framework in which this boundary is incorporated into the semantic and deductive machinery, and outline how this framework can be used to model various situations in which informational entropy arises.Keywords: Lattice-based modal logic · Epistemic logic · Concept lattice · Graphbased semantics · Polarity-based semantics ⋆ The research of the third author is supported by the NWO Vidi grant 016.138.314, the NWO Aspasia grant 015.008.054, and a Delft Technology Fellowship awarded in 2013.
PreliminariesNotation. We let ∆ U denote the identity relation on a set U, and we will drop the subscript when it causes no ambiguity. The superscript (·) c denotes the relative complement of the subset of a given set. Hence, for any binary relation R ⊆ S × T , we let R c ⊆ S × T be defined by (s, t) ∈ R c iff (s, t) R. For any such R and any S ′ ⊆ S and T ′ ⊆ T , we let R[S ′ ] := {t ∈ T | (s, t) ∈ R for some s ∈ S ′ } and R −1 [T ′ ] := {s ∈ S | (s, t) ∈ R for some t ∈ T ′ }, and write R[s] and R −1 [t] for R[{s}] and R −1 [{t}], respectively. Any such R gives rise to the semantic modal operators R , [R] : P(T ) → P(S ) s.t. R W := R −1 [W] and [R]W := (R −1 [W c ]) c for any W ⊆ T . For any T ⊆ U × V, and any U ′ ⊆ U and V ′ ⊆ V, letKnown properties of this construction (cf. [14,) are collected below.. 4. T (1) [U ′ ] = T (1) [T (0) [T (1) [U ′ ]]] and T (0) [V ′ ] = T (0) [T (1) [T (0) [V ′ ]]]. 5. T (0) [ V] = V ′ ∈V T (0) [V ′ ] and T (1) [ U] = U ′ ∈U T (1) [U ′ ].