Theory Order_Union

(*  Title:      HOL/Cardinals/Order_Union.thy
    Author:     Andrei Popescu, TU Muenchen

The ordinal-like sum of two orders with disjoint fields
*)

section ‹Order Union›

theory Order_Union
  imports Main
begin

definition Osum :: "'a rel  'a rel  'a rel"  (infix "Osum" 60) where
  "r Osum r' = r  r'  {(a, a'). a  Field r  a'  Field r'}"

notation Osum  (infix "∪o" 60)

lemma Field_Osum: "Field (r ∪o r') = Field r  Field r'"
  unfolding Osum_def Field_def by blast

lemma Osum_wf:
  assumes FLD: "Field r Int Field r' = {}" and
    WF: "wf r" and WF': "wf r'"
  shows "wf (r Osum r')"
  unfolding wf_eq_minimal2 unfolding Field_Osum
proof(intro allI impI, elim conjE)
  fix A assume *: "A  Field r  Field r'" and **: "A  {}"
  obtain B where B_def: "B = A Int Field r" by blast
  show "aA. a'A. (a', a)  r ∪o r'"
  proof(cases "B = {}")
    assume Case1: "B  {}"
    hence "B  {}  B  Field r" using B_def by auto
    then obtain a where 1: "a  B" and 2: "a1  B. (a1,a)  r"
      using WF unfolding wf_eq_minimal2 by blast
    hence 3: "a  Field r  a  Field r'" using B_def FLD by auto
        (*  *)
    have "a1  A. (a1,a)  r Osum r'"
    proof(intro ballI)
      fix a1 assume **: "a1  A"
      {assume Case11: "a1  Field r"
        hence "(a1,a)  r" using B_def ** 2 by auto
        moreover
        have "(a1,a)  r'" using 3 by (auto simp add: Field_def)
        ultimately have "(a1,a)  r Osum r'"
          using 3 unfolding Osum_def by auto
      }
      moreover
      {assume Case12: "a1  Field r"
        hence "(a1,a)  r" unfolding Field_def by auto
        moreover
        have "(a1,a)  r'" using 3 unfolding Field_def by auto
        ultimately have "(a1,a)  r Osum r'"
          using 3 unfolding Osum_def by auto
      }
      ultimately show "(a1,a)  r Osum r'" by blast
    qed
    thus ?thesis using 1 B_def by auto
  next
    assume Case2: "B = {}"
    hence 1: "A  {}  A  Field r'" using * ** B_def by auto
    then obtain a' where 2: "a'  A" and 3: "a1'  A. (a1',a')  r'"
      using WF' unfolding wf_eq_minimal2 by blast
    hence 4: "a'  Field r'  a'  Field r" using 1 FLD by blast
        (*  *)
    have "a1'  A. (a1',a')  r Osum r'"
    proof(unfold Osum_def, auto simp add: 3)
      fix a1' assume "(a1', a')  r"
      thus False using 4 unfolding Field_def by blast
    next
      fix a1' assume "a1'  A" and "a1'  Field r"
      thus False using Case2 B_def by auto
    qed
    thus ?thesis using 2 by blast
  qed
qed

lemma Osum_Refl:
  assumes FLD: "Field r Int Field r' = {}" and
    REFL: "Refl r" and REFL': "Refl r'"
  shows "Refl (r Osum r')"
  using assms
  unfolding refl_on_def Field_Osum unfolding Osum_def by blast

lemma Osum_trans:
  assumes FLD: "Field r Int Field r' = {}" and
    TRANS: "trans r" and TRANS': "trans r'"
  shows "trans (r Osum r')"
  using assms unfolding Osum_def trans_def disjoint_iff Field_iff by blast

lemma Osum_Preorder:
  "Field r Int Field r' = {}; Preorder r; Preorder r'  Preorder (r Osum r')"
  unfolding preorder_on_def using Osum_Refl Osum_trans by blast

lemma Osum_antisym:
  assumes FLD: "Field r Int Field r' = {}" and
    AN: "antisym r" and AN': "antisym r'"
  shows "antisym (r Osum r')"
  using assms by (auto simp: disjoint_iff antisym_def Osum_def Field_def)

lemma Osum_Partial_order:
  "Field r Int Field r' = {}; Partial_order r; Partial_order r' 
 Partial_order (r Osum r')"
  unfolding partial_order_on_def using Osum_Preorder Osum_antisym by blast

lemma Osum_Total:
  assumes FLD: "Field r Int Field r' = {}" and
    TOT: "Total r" and TOT': "Total r'"
  shows "Total (r Osum r')"
  using assms
  unfolding total_on_def  Field_Osum unfolding Osum_def by blast

lemma Osum_Linear_order:
  "Field r Int Field r' = {}; Linear_order r; Linear_order r'  Linear_order (r Osum r')"
  by (simp add: Osum_Partial_order Osum_Total linear_order_on_def)

lemma Osum_minus_Id1:
  assumes "r  Id"
  shows "(r Osum r') - Id  (r' - Id)  (Field r × Field r')"
using assms by (force simp: Osum_def)

lemma Osum_minus_Id2:
  assumes "r'  Id"
  shows "(r Osum r') - Id  (r - Id)  (Field r × Field r')"
using assms by (force simp: Osum_def)

lemma Osum_minus_Id:
  assumes TOT: "Total r" and TOT': "Total r'" and
    NID: "¬ (r  Id)" and NID': "¬ (r'  Id)"
  shows "(r Osum r') - Id  (r - Id) Osum (r' - Id)"
  using assms Total_Id_Field by (force simp: Osum_def)

lemma wf_Int_Times:
  assumes "A Int B = {}"
  shows "wf(A × B)"
  unfolding wf_def using assms by blast

lemma Osum_wf_Id:
  assumes TOT: "Total r" and TOT': "Total r'" and
    FLD: "Field r Int Field r' = {}" and
    WF: "wf(r - Id)" and WF': "wf(r' - Id)"
  shows "wf ((r Osum r') - Id)"
proof(cases "r  Id  r'  Id")
  assume Case1: "¬(r  Id  r'  Id)"
  have "Field(r - Id) Int Field(r' - Id) = {}"
    using Case1 FLD TOT TOT' Total_Id_Field by blast
  thus ?thesis
    by (meson Case1 Osum_minus_Id Osum_wf TOT TOT' WF WF' wf_subset)
next
  have 1: "wf(Field r × Field r')"
    using FLD by (auto simp add: wf_Int_Times)
  assume Case2: "r  Id  r'  Id"
  moreover
  {assume Case21: "r  Id"
    hence "(r Osum r') - Id  (r' - Id)  (Field r × Field r')"
      using Osum_minus_Id1[of r r'] by simp
    moreover
    {have "Domain(Field r × Field r') Int Range(r' - Id) = {}"
        using FLD unfolding Field_def by blast
      hence "wf((r' - Id)  (Field r × Field r'))"
        using 1 WF' wf_Un[of "Field r × Field r'" "r' - Id"]
        by (auto simp add: Un_commute)
    }
    ultimately have ?thesis using wf_subset by blast
  }
  moreover
  {assume Case22: "r'  Id"
    hence "(r Osum r') - Id  (r - Id)  (Field r × Field r')"
      using Osum_minus_Id2[of r' r] by simp
    moreover
    {have "Range(Field r × Field r') Int Domain(r - Id) = {}"
        using FLD unfolding Field_def by blast
      hence "wf((r - Id)  (Field r × Field r'))"
        using 1 WF wf_Un[of "r - Id" "Field r × Field r'"]
        by (auto simp add: Un_commute)
    }
    ultimately have ?thesis using wf_subset by blast
  }
  ultimately show ?thesis by blast
qed

lemma Osum_Well_order:
  assumes FLD: "Field r Int Field r' = {}" and
    WELL: "Well_order r" and WELL': "Well_order r'"
  shows "Well_order (r Osum r')"
proof-
  have "Total r  Total r'" using WELL WELL'
    by (auto simp add: order_on_defs)
  thus ?thesis using assms unfolding well_order_on_def
    using Osum_Linear_order Osum_wf_Id by blast
qed

end