Set idioms theory "finite intersection_of open", etc.

--- a/src/HOL/Library/Library.thy	Sun Sep 16 22:45:34 2018 +0200
+++ b/src/HOL/Library/Library.thy	Mon Sep 17 15:31:55 2018 +0100
@@ -77,6 +77,7 @@
   Rewrite
   Saturated
   Set_Algebras
+  Set_Idioms
   State_Monad
   Stirling
   Stream

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/HOL/Library/Set_Idioms.thy	Mon Sep 17 15:31:55 2018 +0100
@@ -0,0 +1,551 @@
+(*  Title:      HOL/Library/Set_Idioms.thy
+    Author:     Lawrence Paulson (but borrowed from HOL Light)
+*)
+
+section \<open>Set Idioms\<close>
+
+theory Set_Idioms
+imports Countable_Set
+
+begin
+
+
+subsection\<open>Idioms for being a suitable union/intersection of something\<close>
+
+definition union_of :: "('a set set \<Rightarrow> bool) \<Rightarrow> ('a set \<Rightarrow> bool) \<Rightarrow> 'a set \<Rightarrow> bool"
+  (infixr "union'_of" 60)
+  where "P union_of Q \<equiv> \<lambda>S. \<exists>\<U>. P \<U> \<and> \<U> \<subseteq> Collect Q \<and> \<Union>\<U> = S"
+
+definition intersection_of :: "('a set set \<Rightarrow> bool) \<Rightarrow> ('a set \<Rightarrow> bool) \<Rightarrow> 'a set \<Rightarrow> bool"
+  (infixr "intersection'_of" 60)
+  where "P intersection_of Q \<equiv> \<lambda>S. \<exists>\<U>. P \<U> \<and> \<U> \<subseteq> Collect Q \<and> \<Inter>\<U> = S"
+
+definition arbitrary:: "'a set set \<Rightarrow> bool" where "arbitrary \<U> \<equiv> True"
+
+lemma union_of_inc: "\<lbrakk>P {S}; Q S\<rbrakk> \<Longrightarrow> (P union_of Q) S"
+  by (auto simp: union_of_def)
+
+lemma intersection_of_inc:
+   "\<lbrakk>P {S}; Q S\<rbrakk> \<Longrightarrow> (P intersection_of Q) S"
+  by (auto simp: intersection_of_def)
+
+lemma union_of_mono:
+   "\<lbrakk>(P union_of Q) S; \<And>x. Q x \<Longrightarrow> Q' x\<rbrakk> \<Longrightarrow> (P union_of Q') S"
+  by (auto simp: union_of_def)
+
+lemma intersection_of_mono:
+   "\<lbrakk>(P intersection_of Q) S; \<And>x. Q x \<Longrightarrow> Q' x\<rbrakk> \<Longrightarrow> (P intersection_of Q') S"
+  by (auto simp: intersection_of_def)
+
+lemma all_union_of:
+     "(\<forall>S. (P union_of Q) S \<longrightarrow> R S) \<longleftrightarrow> (\<forall>T. P T \<and> T \<subseteq> Collect Q \<longrightarrow> R(\<Union>T))"
+  by (auto simp: union_of_def)
+
+lemma all_intersection_of:
+     "(\<forall>S. (P intersection_of Q) S \<longrightarrow> R S) \<longleftrightarrow> (\<forall>T. P T \<and> T \<subseteq> Collect Q \<longrightarrow> R(\<Inter>T))"
+  by (auto simp: intersection_of_def)
+
+lemma union_of_empty:
+     "P {} \<Longrightarrow> (P union_of Q) {}"
+  by (auto simp: union_of_def)
+
+lemma intersection_of_empty:
+     "P {} \<Longrightarrow> (P intersection_of Q) UNIV"
+  by (auto simp: intersection_of_def)
+
+text\<open> The arbitrary and finite cases\<close>
+
+lemma arbitrary_union_of_alt:
+   "(arbitrary union_of Q) S \<longleftrightarrow> (\<forall>x \<in> S. \<exists>U. Q U \<and> x \<in> U \<and> U \<subseteq> S)"
+ (is "?lhs = ?rhs")
+proof
+  assume ?lhs
+  then show ?rhs
+    by (force simp: union_of_def arbitrary_def)
+next
+  assume ?rhs
+  then have "{U. Q U \<and> U \<subseteq> S} \<subseteq> Collect Q" "\<Union>{U. Q U \<and> U \<subseteq> S} = S"
+    by auto
+  then show ?lhs
+    unfolding union_of_def arbitrary_def by blast
+qed
+
+lemma arbitrary_union_of_empty [simp]: "(arbitrary union_of P) {}"
+  by (force simp: union_of_def arbitrary_def)
+
+lemma arbitrary_intersection_of_empty [simp]:
+  "(arbitrary intersection_of P) UNIV"
+  by (force simp: intersection_of_def arbitrary_def)
+
+lemma arbitrary_union_of_inc:
+  "P S \<Longrightarrow> (arbitrary union_of P) S"
+  by (force simp: union_of_inc arbitrary_def)
+
+lemma arbitrary_intersection_of_inc:
+  "P S \<Longrightarrow> (arbitrary intersection_of P) S"
+  by (force simp: intersection_of_inc arbitrary_def)
+
+lemma arbitrary_union_of_complement:
+   "(arbitrary union_of P) S \<longleftrightarrow> (arbitrary intersection_of (\<lambda>S. P(- S))) (- S)"  (is "?lhs = ?rhs")
+proof
+  assume ?lhs
+  then obtain \<U> where "\<U> \<subseteq> Collect P" "S = \<Union>\<U>"
+    by (auto simp: union_of_def arbitrary_def)
+  then show ?rhs
+    unfolding intersection_of_def arbitrary_def
+    by (rule_tac x="uminus ` \<U>" in exI) auto
+next
+  assume ?rhs
+  then obtain \<U> where "\<U> \<subseteq> {S. P (- S)}" "\<Inter>\<U> = - S"
+    by (auto simp: union_of_def intersection_of_def arbitrary_def)
+  then show ?lhs
+    unfolding union_of_def arbitrary_def
+    by (rule_tac x="uminus ` \<U>" in exI) auto
+qed
+
+lemma arbitrary_intersection_of_complement:
+   "(arbitrary intersection_of P) S \<longleftrightarrow> (arbitrary union_of (\<lambda>S. P(- S))) (- S)"
+  by (simp add: arbitrary_union_of_complement)
+
+lemma arbitrary_union_of_idempot [simp]:
+  "arbitrary union_of arbitrary union_of P = arbitrary union_of P"
+proof -
+  have 1: "\<exists>\<U>'\<subseteq>Collect P. \<Union>\<U>' = \<Union>\<U>" if "\<U> \<subseteq> {S. \<exists>\<V>\<subseteq>Collect P. \<Union>\<V> = S}" for \<U>
+  proof -
+    let ?\<W> = "{V. \<exists>\<V>. \<V>\<subseteq>Collect P \<and> V \<in> \<V> \<and> (\<exists>S \<in> \<U>. \<Union>\<V> = S)}"
+    have *: "\<And>x U. \<lbrakk>x \<in> U; U \<in> \<U>\<rbrakk> \<Longrightarrow> x \<in> \<Union>?\<W>"
+      using that
+      apply simp
+      apply (drule subsetD, assumption, auto)
+      done
+    show ?thesis
+    apply (rule_tac x="{V. \<exists>\<V>. \<V>\<subseteq>Collect P \<and> V \<in> \<V> \<and> (\<exists>S \<in> \<U>. \<Union>\<V> = S)}" in exI)
+      using that by (blast intro: *)
+  qed
+  have 2: "\<exists>\<U>'\<subseteq>{S. \<exists>\<U>\<subseteq>Collect P. \<Union>\<U> = S}. \<Union>\<U>' = \<Union>\<U>" if "\<U> \<subseteq> Collect P" for \<U>
+    by (metis (mono_tags, lifting) union_of_def arbitrary_union_of_inc that)
+  show ?thesis
+    unfolding union_of_def arbitrary_def by (force simp: 1 2)
+qed
+
+lemma arbitrary_intersection_of_idempot:
+   "arbitrary intersection_of arbitrary intersection_of P = arbitrary intersection_of P" (is "?lhs = ?rhs")
+proof -
+  have "- ?lhs = - ?rhs"
+    unfolding arbitrary_intersection_of_complement by simp
+  then show ?thesis
+    by simp
+qed
+
+lemma arbitrary_union_of_Union:
+   "(\<And>S. S \<in> \<U> \<Longrightarrow> (arbitrary union_of P) S) \<Longrightarrow> (arbitrary union_of P) (\<Union>\<U>)"
+  by (metis union_of_def arbitrary_def arbitrary_union_of_idempot mem_Collect_eq subsetI)
+
+lemma arbitrary_union_of_Un:
+   "\<lbrakk>(arbitrary union_of P) S; (arbitrary union_of P) T\<rbrakk>
+           \<Longrightarrow> (arbitrary union_of P) (S \<union> T)"
+  using arbitrary_union_of_Union [of "{S,T}"] by auto
+
+lemma arbitrary_intersection_of_Inter:
+   "(\<And>S. S \<in> \<U> \<Longrightarrow> (arbitrary intersection_of P) S) \<Longrightarrow> (arbitrary intersection_of P) (\<Inter>\<U>)"
+  by (metis intersection_of_def arbitrary_def arbitrary_intersection_of_idempot mem_Collect_eq subsetI)
+
+lemma arbitrary_intersection_of_Int:
+   "\<lbrakk>(arbitrary intersection_of P) S; (arbitrary intersection_of P) T\<rbrakk>
+           \<Longrightarrow> (arbitrary intersection_of P) (S \<inter> T)"
+  using arbitrary_intersection_of_Inter [of "{S,T}"] by auto
+
+lemma arbitrary_union_of_Int_eq:
+  "(\<forall>S T. (arbitrary union_of P) S \<and> (arbitrary union_of P) T
+               \<longrightarrow> (arbitrary union_of P) (S \<inter> T))
+   \<longleftrightarrow> (\<forall>S T. P S \<and> P T \<longrightarrow> (arbitrary union_of P) (S \<inter> T))"  (is "?lhs = ?rhs")
+proof
+  assume ?lhs
+  then show ?rhs
+    by (simp add: arbitrary_union_of_inc)
+next
+  assume R: ?rhs
+  show ?lhs
+  proof clarify
+    fix S :: "'a set" and T :: "'a set"
+    assume "(arbitrary union_of P) S" and "(arbitrary union_of P) T"
+    then obtain \<U> \<V> where *: "\<U> \<subseteq> Collect P" "\<Union>\<U> = S" "\<V> \<subseteq> Collect P" "\<Union>\<V> = T"
+      by (auto simp: union_of_def)
+    then have "(arbitrary union_of P) (\<Union>C\<in>\<U>. \<Union>D\<in>\<V>. C \<inter> D)"
+     using R by (blast intro: arbitrary_union_of_Union)
+   then show "(arbitrary union_of P) (S \<inter> T)"
+     by (simp add: Int_UN_distrib2 *)
+ qed
+qed
+
+lemma arbitrary_intersection_of_Un_eq:
+   "(\<forall>S T. (arbitrary intersection_of P) S \<and> (arbitrary intersection_of P) T
+               \<longrightarrow> (arbitrary intersection_of P) (S \<union> T)) \<longleftrightarrow>
+        (\<forall>S T. P S \<and> P T \<longrightarrow> (arbitrary intersection_of P) (S \<union> T))"
+  apply (simp add: arbitrary_intersection_of_complement)
+  using arbitrary_union_of_Int_eq [of "\<lambda>S. P (- S)"]
+  by (metis (no_types, lifting) arbitrary_def double_compl union_of_inc)
+
+lemma finite_union_of_empty [simp]: "(finite union_of P) {}"
+  by (simp add: union_of_empty)
+
+lemma finite_intersection_of_empty [simp]: "(finite intersection_of P) UNIV"
+  by (simp add: intersection_of_empty)
+
+lemma finite_union_of_inc:
+   "P S \<Longrightarrow> (finite union_of P) S"
+  by (simp add: union_of_inc)
+
+lemma finite_intersection_of_inc:
+   "P S \<Longrightarrow> (finite intersection_of P) S"
+  by (simp add: intersection_of_inc)
+
+lemma finite_union_of_complement:
+  "(finite union_of P) S \<longleftrightarrow> (finite intersection_of (\<lambda>S. P(- S))) (- S)"
+  unfolding union_of_def intersection_of_def
+  apply safe
+   apply (rule_tac x="uminus ` \<U>" in exI, fastforce)+
+  done
+
+lemma finite_intersection_of_complement:
+   "(finite intersection_of P) S \<longleftrightarrow> (finite union_of (\<lambda>S. P(- S))) (- S)"
+  by (simp add: finite_union_of_complement)
+
+lemma finite_union_of_idempot [simp]:
+  "finite union_of finite union_of P = finite union_of P"
+proof -
+  have "(finite union_of P) S" if S: "(finite union_of finite union_of P) S" for S
+  proof -
+    obtain \<U> where "finite \<U>" "S = \<Union>\<U>" and \<U>: "\<forall>U\<in>\<U>. \<exists>\<U>. finite \<U> \<and> (\<U> \<subseteq> Collect P) \<and> \<Union>\<U> = U"
+      using S unfolding union_of_def by (auto simp: subset_eq)
+    then obtain f where "\<forall>U\<in>\<U>. finite (f U) \<and> (f U \<subseteq> Collect P) \<and> \<Union>(f U) = U"
+      by metis
+    then show ?thesis
+      unfolding union_of_def \<open>S = \<Union>\<U>\<close>
+      by (rule_tac x = "snd ` Sigma \<U> f" in exI) (fastforce simp: \<open>finite \<U>\<close>)
+  qed
+  moreover
+  have "(finite union_of finite union_of P) S" if "(finite union_of P) S" for S
+    by (simp add: finite_union_of_inc that)
+  ultimately show ?thesis
+    by force
+qed
+
+lemma finite_intersection_of_idempot [simp]:
+   "finite intersection_of finite intersection_of P = finite intersection_of P"
+  by (force simp: finite_intersection_of_complement)
+
+lemma finite_union_of_Union:
+   "\<lbrakk>finite \<U>; \<And>S. S \<in> \<U> \<Longrightarrow> (finite union_of P) S\<rbrakk> \<Longrightarrow> (finite union_of P) (\<Union>\<U>)"
+  using finite_union_of_idempot [of P]
+  by (metis mem_Collect_eq subsetI union_of_def)
+
+lemma finite_union_of_Un:
+   "\<lbrakk>(finite union_of P) S; (finite union_of P) T\<rbrakk> \<Longrightarrow> (finite union_of P) (S \<union> T)"
+  by (auto simp: union_of_def)
+
+lemma finite_intersection_of_Inter:
+   "\<lbrakk>finite \<U>; \<And>S. S \<in> \<U> \<Longrightarrow> (finite intersection_of P) S\<rbrakk> \<Longrightarrow> (finite intersection_of P) (\<Inter>\<U>)"
+  using finite_intersection_of_idempot [of P]
+  by (metis intersection_of_def mem_Collect_eq subsetI)
+
+lemma finite_intersection_of_Int:
+   "\<lbrakk>(finite intersection_of P) S; (finite intersection_of P) T\<rbrakk>
+           \<Longrightarrow> (finite intersection_of P) (S \<inter> T)"
+  by (auto simp: intersection_of_def)
+
+lemma finite_union_of_Int_eq:
+   "(\<forall>S T. (finite union_of P) S \<and> (finite union_of P) T \<longrightarrow> (finite union_of P) (S \<inter> T))
+    \<longleftrightarrow> (\<forall>S T. P S \<and> P T \<longrightarrow> (finite union_of P) (S \<inter> T))"
+(is "?lhs = ?rhs")
+proof
+  assume ?lhs
+  then show ?rhs
+    by (simp add: finite_union_of_inc)
+next
+  assume R: ?rhs
+  show ?lhs
+  proof clarify
+    fix S :: "'a set" and T :: "'a set"
+    assume "(finite union_of P) S" and "(finite union_of P) T"
+    then obtain \<U> \<V> where *: "\<U> \<subseteq> Collect P" "\<Union>\<U> = S" "finite \<U>" "\<V> \<subseteq> Collect P" "\<Union>\<V> = T" "finite \<V>"
+      by (auto simp: union_of_def)
+    then have "(finite union_of P) (\<Union>C\<in>\<U>. \<Union>D\<in>\<V>. C \<inter> D)"
+      using R
+      by (blast intro: finite_union_of_Union)
+   then show "(finite union_of P) (S \<inter> T)"
+     by (simp add: Int_UN_distrib2 *)
+ qed
+qed
+
+lemma finite_intersection_of_Un_eq:
+   "(\<forall>S T. (finite intersection_of P) S \<and>
+               (finite intersection_of P) T
+               \<longrightarrow> (finite intersection_of P) (S \<union> T)) \<longleftrightarrow>
+        (\<forall>S T. P S \<and> P T \<longrightarrow> (finite intersection_of P) (S \<union> T))"
+  apply (simp add: finite_intersection_of_complement)
+  using finite_union_of_Int_eq [of "\<lambda>S. P (- S)"]
+  by (metis (no_types, lifting) double_compl)
+
+
+abbreviation finite' :: "'a set \<Rightarrow> bool"
+  where "finite' A \<equiv> finite A \<and> A \<noteq> {}"
+
+lemma finite'_intersection_of_Int:
+   "\<lbrakk>(finite' intersection_of P) S; (finite' intersection_of P) T\<rbrakk>
+           \<Longrightarrow> (finite' intersection_of P) (S \<inter> T)"
+  by (auto simp: intersection_of_def)
+
+lemma finite'_intersection_of_inc:
+   "P S \<Longrightarrow> (finite' intersection_of P) S"
+  by (simp add: intersection_of_inc)
+
+
+subsection \<open>The ``Relative to'' operator\<close>
+
+text\<open>A somewhat cheap but handy way of getting localized forms of various topological concepts
+(open, closed, borel, fsigma, gdelta etc.)\<close>
+
+definition relative_to :: "['a set \<Rightarrow> bool, 'a set, 'a set] \<Rightarrow> bool" (infixl "relative'_to" 55)
+  where "P relative_to S \<equiv> \<lambda>T. \<exists>U. P U \<and> S \<inter> U = T"
+
+lemma relative_to_UNIV [simp]: "(P relative_to UNIV) S \<longleftrightarrow> P S"
+  by (simp add: relative_to_def)
+
+lemma relative_to_imp_subset:
+   "(P relative_to S) T \<Longrightarrow> T \<subseteq> S"
+  by (auto simp: relative_to_def)
+
+lemma all_relative_to: "(\<forall>S. (P relative_to U) S \<longrightarrow> Q S) \<longleftrightarrow> (\<forall>S. P S \<longrightarrow> Q(U \<inter> S))"
+  by (auto simp: relative_to_def)
+
+lemma relative_to_inc:
+   "P S \<Longrightarrow> (P relative_to U) (U \<inter> S)"
+  by (auto simp: relative_to_def)
+
+lemma relative_to_relative_to [simp]:
+   "P relative_to S relative_to T = P relative_to (S \<inter> T)"
+  unfolding relative_to_def
+  by auto
+
+lemma relative_to_compl:
+   "S \<subseteq> U \<Longrightarrow> ((P relative_to U) (U - S) \<longleftrightarrow> ((\<lambda>c. P(- c)) relative_to U) S)"
+  unfolding relative_to_def
+  by (metis Diff_Diff_Int Diff_eq double_compl inf.absorb_iff2)
+
+lemma relative_to_subset:
+   "S \<subseteq> T \<and> P S \<Longrightarrow> (P relative_to T) S"
+  unfolding relative_to_def by auto
+
+lemma relative_to_subset_trans:
+   "(P relative_to U) S \<and> S \<subseteq> T \<and> T \<subseteq> U \<Longrightarrow> (P relative_to T) S"
+  unfolding relative_to_def by auto
+
+lemma relative_to_mono:
+   "\<lbrakk>(P relative_to U) S; \<And>S. P S \<Longrightarrow> Q S\<rbrakk> \<Longrightarrow> (Q relative_to U) S"
+  unfolding relative_to_def by auto
+
+lemma relative_to_subset_inc: "\<lbrakk>S \<subseteq> U; P S\<rbrakk> \<Longrightarrow> (P relative_to U) S"
+  unfolding relative_to_def by auto
+
+lemma relative_to_Int:
+   "\<lbrakk>(P relative_to S) C; (P relative_to S) D; \<And>X Y. \<lbrakk>P X; P Y\<rbrakk> \<Longrightarrow> P(X \<inter> Y)\<rbrakk>
+         \<Longrightarrow>  (P relative_to S) (C \<inter> D)"
+  unfolding relative_to_def by auto
+
+lemma relative_to_Un:
+   "\<lbrakk>(P relative_to S) C; (P relative_to S) D; \<And>X Y. \<lbrakk>P X; P Y\<rbrakk> \<Longrightarrow> P(X \<union> Y)\<rbrakk>
+         \<Longrightarrow>  (P relative_to S) (C \<union> D)"
+  unfolding relative_to_def by auto
+
+lemma arbitrary_union_of_relative_to:
+  "((arbitrary union_of P) relative_to U) = (arbitrary union_of (P relative_to U))" (is "?lhs = ?rhs")
+proof -
+  have "?rhs S" if L: "?lhs S" for S
+  proof -
+    obtain \<U> where "S = U \<inter> \<Union>\<U>" "\<U> \<subseteq> Collect P"
+      using L unfolding relative_to_def union_of_def by auto
+    then show ?thesis
+      unfolding relative_to_def union_of_def arbitrary_def
+      by (rule_tac x="(\<lambda>X. U \<inter> X) ` \<U>" in exI) auto
+  qed
+  moreover have "?lhs S" if R: "?rhs S" for S
+  proof -
+    obtain \<U> where "S = \<Union>\<U>" "\<forall>T\<in>\<U>. \<exists>V. P V \<and> U \<inter> V = T"
+      using R unfolding relative_to_def union_of_def by auto
+    then obtain f where f: "\<And>T. T \<in> \<U> \<Longrightarrow> P (f T)" "\<And>T. T \<in> \<U> \<Longrightarrow> U \<inter> (f T) = T"
+      by metis
+    then have "\<exists>\<U>'\<subseteq>Collect P. \<Union>\<U>' = UNION \<U> f"
+      by (metis image_subset_iff mem_Collect_eq)
+    moreover have eq: "U \<inter> UNION \<U> f = \<Union>\<U>"
+      using f by auto
+    ultimately show ?thesis
+      unfolding relative_to_def union_of_def arbitrary_def \<open>S = \<Union>\<U>\<close>
+      by metis
+  qed
+  ultimately show ?thesis
+    by blast
+qed
+
+lemma finite_union_of_relative_to:
+  "((finite union_of P) relative_to U) = (finite union_of (P relative_to U))" (is "?lhs = ?rhs")
+proof -
+  have "?rhs S" if L: "?lhs S" for S
+  proof -
+    obtain \<U> where "S = U \<inter> \<Union>\<U>" "\<U> \<subseteq> Collect P" "finite \<U>"
+      using L unfolding relative_to_def union_of_def by auto
+    then show ?thesis
+      unfolding relative_to_def union_of_def
+      by (rule_tac x="(\<lambda>X. U \<inter> X) ` \<U>" in exI) auto
+  qed
+  moreover have "?lhs S" if R: "?rhs S" for S
+  proof -
+    obtain \<U> where "S = \<Union>\<U>" "\<forall>T\<in>\<U>. \<exists>V. P V \<and> U \<inter> V = T" "finite \<U>"
+      using R unfolding relative_to_def union_of_def by auto
+    then obtain f where f: "\<And>T. T \<in> \<U> \<Longrightarrow> P (f T)" "\<And>T. T \<in> \<U> \<Longrightarrow> U \<inter> (f T) = T"
+      by metis
+    then have "\<exists>\<U>'\<subseteq>Collect P. \<Union>\<U>' = UNION \<U> f"
+      by (metis image_subset_iff mem_Collect_eq)
+    moreover have eq: "U \<inter> UNION \<U> f = \<Union>\<U>"
+      using f by auto
+    ultimately show ?thesis
+      using \<open>finite \<U>\<close> f
+      unfolding relative_to_def union_of_def \<open>S = \<Union>\<U>\<close>
+      by (rule_tac x="UNION \<U> f" in exI) (metis finite_imageI image_subsetI mem_Collect_eq)
+  qed
+  ultimately show ?thesis
+    by blast
+qed
+
+lemma countable_union_of_relative_to:
+  "((countable union_of P) relative_to U) = (countable union_of (P relative_to U))" (is "?lhs = ?rhs")
+proof -
+  have "?rhs S" if L: "?lhs S" for S
+  proof -
+    obtain \<U> where "S = U \<inter> \<Union>\<U>" "\<U> \<subseteq> Collect P" "countable \<U>"
+      using L unfolding relative_to_def union_of_def by auto
+    then show ?thesis
+      unfolding relative_to_def union_of_def
+      by (rule_tac x="(\<lambda>X. U \<inter> X) ` \<U>" in exI) auto
+  qed
+  moreover have "?lhs S" if R: "?rhs S" for S
+  proof -
+    obtain \<U> where "S = \<Union>\<U>" "\<forall>T\<in>\<U>. \<exists>V. P V \<and> U \<inter> V = T" "countable \<U>"
+      using R unfolding relative_to_def union_of_def by auto
+    then obtain f where f: "\<And>T. T \<in> \<U> \<Longrightarrow> P (f T)" "\<And>T. T \<in> \<U> \<Longrightarrow> U \<inter> (f T) = T"
+      by metis
+    then have "\<exists>\<U>'\<subseteq>Collect P. \<Union>\<U>' = UNION \<U> f"
+      by (metis image_subset_iff mem_Collect_eq)
+    moreover have eq: "U \<inter> UNION \<U> f = \<Union>\<U>"
+      using f by auto
+    ultimately show ?thesis
+      using \<open>countable \<U>\<close> f
+      unfolding relative_to_def union_of_def \<open>S = \<Union>\<U>\<close>
+      by (rule_tac x="UNION \<U> f" in exI) (metis countable_image image_subsetI mem_Collect_eq)
+  qed
+  ultimately show ?thesis
+    by blast
+qed
+
+
+lemma arbitrary_intersection_of_relative_to:
+  "((arbitrary intersection_of P) relative_to U) = ((arbitrary intersection_of (P relative_to U)) relative_to U)" (is "?lhs = ?rhs")
+proof -
+  have "?rhs S" if L: "?lhs S" for S
+  proof -
+    obtain \<U> where \<U>: "S = U \<inter> \<Inter>\<U>" "\<U> \<subseteq> Collect P"
+      using L unfolding relative_to_def intersection_of_def by auto
+    show ?thesis
+      unfolding relative_to_def intersection_of_def arbitrary_def
+    proof (intro exI conjI)
+      show "U \<inter> (\<Inter>X\<in>\<U>. U \<inter> X) = S" "(\<inter>) U ` \<U> \<subseteq> {T. \<exists>Ua. P Ua \<and> U \<inter> Ua = T}"
+        using \<U> by blast+
+    qed auto
+  qed
+  moreover have "?lhs S" if R: "?rhs S" for S
+  proof -
+    obtain \<U> where "S = U \<inter> \<Inter>\<U>" "\<forall>T\<in>\<U>. \<exists>V. P V \<and> U \<inter> V = T"
+      using R unfolding relative_to_def intersection_of_def  by auto
+    then obtain f where f: "\<And>T. T \<in> \<U> \<Longrightarrow> P (f T)" "\<And>T. T \<in> \<U> \<Longrightarrow> U \<inter> (f T) = T"
+      by metis
+    then have "\<exists>\<U>'\<subseteq>Collect P. \<Inter>\<U>' = INTER \<U> f"
+      by (metis image_subset_iff mem_Collect_eq)
+    moreover have eq: "U \<inter> INTER \<U> f = U \<inter> \<Inter>\<U>"
+      using f by auto
+    ultimately show ?thesis
+      unfolding relative_to_def intersection_of_def arbitrary_def \<open>S = U \<inter> \<Inter>\<U>\<close>
+      by metis
+  qed
+  ultimately show ?thesis
+    by blast
+qed
+
+lemma finite_intersection_of_relative_to:
+  "((finite intersection_of P) relative_to U) = ((finite intersection_of (P relative_to U)) relative_to U)" (is "?lhs = ?rhs")
+proof -
+  have "?rhs S" if L: "?lhs S" for S
+  proof -
+    obtain \<U> where \<U>: "S = U \<inter> \<Inter>\<U>" "\<U> \<subseteq> Collect P" "finite \<U>"
+      using L unfolding relative_to_def intersection_of_def by auto
+    show ?thesis
+      unfolding relative_to_def intersection_of_def
+    proof (intro exI conjI)
+      show "U \<inter> (\<Inter>X\<in>\<U>. U \<inter> X) = S" "(\<inter>) U ` \<U> \<subseteq> {T. \<exists>Ua. P Ua \<and> U \<inter> Ua = T}"
+        using \<U> by blast+
+      show "finite ((\<inter>) U ` \<U>)"
+        by (simp add: \<open>finite \<U>\<close>)
+    qed auto
+  qed
+  moreover have "?lhs S" if R: "?rhs S" for S
+  proof -
+    obtain \<U> where "S = U \<inter> \<Inter>\<U>" "\<forall>T\<in>\<U>. \<exists>V. P V \<and> U \<inter> V = T" "finite \<U>"
+      using R unfolding relative_to_def intersection_of_def  by auto
+    then obtain f where f: "\<And>T. T \<in> \<U> \<Longrightarrow> P (f T)" "\<And>T. T \<in> \<U> \<Longrightarrow> U \<inter> (f T) = T"
+      by metis
+    then have "\<exists>\<U>'\<subseteq>Collect P. \<Inter>\<U>' = INTER \<U> f"
+      by (metis image_subset_iff mem_Collect_eq)
+    moreover have eq: "U \<inter> INTER \<U> f = U \<inter> \<Inter>\<U>"
+      using f by auto
+    ultimately show ?thesis
+      unfolding relative_to_def intersection_of_def \<open>S = U \<inter> \<Inter>\<U>\<close>
+      by (metis (no_types, hide_lams) \<open>finite \<U>\<close> f(1) finite_imageI image_subset_iff mem_Collect_eq)
+  qed
+  ultimately show ?thesis
+    by blast
+qed
+
+lemma countable_intersection_of_relative_to:
+  "((countable intersection_of P) relative_to U) = ((countable intersection_of (P relative_to U)) relative_to U)" (is "?lhs = ?rhs")
+proof -
+  have "?rhs S" if L: "?lhs S" for S
+  proof -
+    obtain \<U> where \<U>: "S = U \<inter> \<Inter>\<U>" "\<U> \<subseteq> Collect P" "countable \<U>"
+      using L unfolding relative_to_def intersection_of_def by auto
+    show ?thesis
+      unfolding relative_to_def intersection_of_def
+    proof (intro exI conjI)
+      show "U \<inter> (\<Inter>X\<in>\<U>. U \<inter> X) = S" "(\<inter>) U ` \<U> \<subseteq> {T. \<exists>Ua. P Ua \<and> U \<inter> Ua = T}"
+        using \<U> by blast+
+      show "countable ((\<inter>) U ` \<U>)"
+        by (simp add: \<open>countable \<U>\<close>)
+    qed auto
+  qed
+  moreover have "?lhs S" if R: "?rhs S" for S
+  proof -
+    obtain \<U> where "S = U \<inter> \<Inter>\<U>" "\<forall>T\<in>\<U>. \<exists>V. P V \<and> U \<inter> V = T" "countable \<U>"
+      using R unfolding relative_to_def intersection_of_def  by auto
+    then obtain f where f: "\<And>T. T \<in> \<U> \<Longrightarrow> P (f T)" "\<And>T. T \<in> \<U> \<Longrightarrow> U \<inter> (f T) = T"
+      by metis
+    then have "\<exists>\<U>'\<subseteq>Collect P. \<Inter>\<U>' = INTER \<U> f"
+      by (metis image_subset_iff mem_Collect_eq)
+    moreover have eq: "U \<inter> INTER \<U> f = U \<inter> \<Inter>\<U>"
+      using f by auto
+    ultimately show ?thesis
+      unfolding relative_to_def intersection_of_def \<open>S = U \<inter> \<Inter>\<U>\<close>
+      by (metis (no_types, hide_lams) \<open>countable \<U>\<close> f(1) countable_image image_subset_iff mem_Collect_eq)
+  qed
+  ultimately show ?thesis
+    by blast
+qed
+
+end