PrimitiveObserver

formal source

  49/-- A primitive observer is exactly a primitive interface. This is a naming
  50choice, but it is important: the observer is not external to recognition; it is
  51the interface structure recognition forces. -/
  52abbrev PrimitiveObserver (K : Type*) := PrimitiveInterface K
  53
  54/-- The observer kernel is reflexive. -/
  55theorem kernel_refl {K : Type*} (I : PrimitiveInterface K) (x : K) :
  56    I.kernel x x := rfl
  57
  58/-- The observer kernel is symmetric. -/
  59theorem kernel_symm {K : Type*} (I : PrimitiveInterface K) {x y : K}
  60    (h : I.kernel x y) : I.kernel y x := h.symm
  61
  62/-- The observer kernel is transitive. -/
  63theorem kernel_trans {K : Type*} (I : PrimitiveInterface K) {x y z : K}
  64    (hxy : I.kernel x y) (hyz : I.kernel y z) : I.kernel x z :=
  65  hxy.trans hyz
  66
  67/-- Every primitive interface partitions its carrier into observational
  68equivalence classes. -/
  69theorem kernel_is_equivalence {K : Type*} (I : PrimitiveInterface K) :
  70    Equivalence (I.kernel) :=
  71  ⟨kernel_refl I,
  72   fun {x y} h => kernel_symm I (x := x) (y := y) h,
  73   fun {x y z} h₁ h₂ => kernel_trans I (x := x) (y := y) (z := z) h₁ h₂⟩
  74
  75/-! ## Non-Trivial Recognition -/
  76
  77/-- A carrier has non-trivial recognition when at least two configurations are
  78distinguishable. At the primitive floor this is simply the existence of a
  79non-equality. -/
  80def NontrivialRecognition (K : Type*) : Prop :=
  81  ∃ x y : K, equalityDistinction K x y
  82