src/HOL/Relation.thy
 author nipkow Wed Feb 11 10:51:07 2009 +0100 (2009-02-11) changeset 29859 33bff35f1335 parent 29609 a010aab5bed0 child 30198 922f944f03b2 permissions -rw-r--r--
Moved Order_Relation into Library and moved some of it into Relation.
```     1 (*  Title:      HOL/Relation.thy
```
```     2     Author:     Lawrence C Paulson, Cambridge University Computer Laboratory
```
```     3     Copyright   1996  University of Cambridge
```
```     4 *)
```
```     5
```
```     6 header {* Relations *}
```
```     7
```
```     8 theory Relation
```
```     9 imports Datatype Finite_Set
```
```    10 begin
```
```    11
```
```    12 subsection {* Definitions *}
```
```    13
```
```    14 definition
```
```    15   converse :: "('a * 'b) set => ('b * 'a) set"
```
```    16     ("(_^-1)" [1000] 999) where
```
```    17   "r^-1 == {(y, x). (x, y) : r}"
```
```    18
```
```    19 notation (xsymbols)
```
```    20   converse  ("(_\<inverse>)" [1000] 999)
```
```    21
```
```    22 definition
```
```    23   rel_comp  :: "[('b * 'c) set, ('a * 'b) set] => ('a * 'c) set"
```
```    24     (infixr "O" 75) where
```
```    25   "r O s == {(x,z). EX y. (x, y) : s & (y, z) : r}"
```
```    26
```
```    27 definition
```
```    28   Image :: "[('a * 'b) set, 'a set] => 'b set"
```
```    29     (infixl "``" 90) where
```
```    30   "r `` s == {y. EX x:s. (x,y):r}"
```
```    31
```
```    32 definition
```
```    33   Id :: "('a * 'a) set" where -- {* the identity relation *}
```
```    34   "Id == {p. EX x. p = (x,x)}"
```
```    35
```
```    36 definition
```
```    37   diag  :: "'a set => ('a * 'a) set" where -- {* diagonal: identity over a set *}
```
```    38   "diag A == \<Union>x\<in>A. {(x,x)}"
```
```    39
```
```    40 definition
```
```    41   Domain :: "('a * 'b) set => 'a set" where
```
```    42   "Domain r == {x. EX y. (x,y):r}"
```
```    43
```
```    44 definition
```
```    45   Range  :: "('a * 'b) set => 'b set" where
```
```    46   "Range r == Domain(r^-1)"
```
```    47
```
```    48 definition
```
```    49   Field :: "('a * 'a) set => 'a set" where
```
```    50   "Field r == Domain r \<union> Range r"
```
```    51
```
```    52 definition
```
```    53   refl :: "['a set, ('a * 'a) set] => bool" where -- {* reflexivity over a set *}
```
```    54   "refl A r == r \<subseteq> A \<times> A & (ALL x: A. (x,x) : r)"
```
```    55
```
```    56 abbreviation
```
```    57   reflexive :: "('a * 'a) set => bool" where -- {* reflexivity over a type *}
```
```    58   "reflexive == refl UNIV"
```
```    59
```
```    60 definition
```
```    61   sym :: "('a * 'a) set => bool" where -- {* symmetry predicate *}
```
```    62   "sym r == ALL x y. (x,y): r --> (y,x): r"
```
```    63
```
```    64 definition
```
```    65   antisym :: "('a * 'a) set => bool" where -- {* antisymmetry predicate *}
```
```    66   "antisym r == ALL x y. (x,y):r --> (y,x):r --> x=y"
```
```    67
```
```    68 definition
```
```    69   trans :: "('a * 'a) set => bool" where -- {* transitivity predicate *}
```
```    70   "trans r == (ALL x y z. (x,y):r --> (y,z):r --> (x,z):r)"
```
```    71
```
```    72 definition
```
```    73 irrefl :: "('a * 'a) set => bool" where
```
```    74 "irrefl r \<equiv> \<forall>x. (x,x) \<notin> r"
```
```    75
```
```    76 definition
```
```    77 total_on :: "'a set => ('a * 'a) set => bool" where
```
```    78 "total_on A r \<equiv> \<forall>x\<in>A.\<forall>y\<in>A. x\<noteq>y \<longrightarrow> (x,y)\<in>r \<or> (y,x)\<in>r"
```
```    79
```
```    80 abbreviation "total \<equiv> total_on UNIV"
```
```    81
```
```    82 definition
```
```    83   single_valued :: "('a * 'b) set => bool" where
```
```    84   "single_valued r == ALL x y. (x,y):r --> (ALL z. (x,z):r --> y=z)"
```
```    85
```
```    86 definition
```
```    87   inv_image :: "('b * 'b) set => ('a => 'b) => ('a * 'a) set" where
```
```    88   "inv_image r f == {(x, y). (f x, f y) : r}"
```
```    89
```
```    90
```
```    91 subsection {* The identity relation *}
```
```    92
```
```    93 lemma IdI [intro]: "(a, a) : Id"
```
```    94 by (simp add: Id_def)
```
```    95
```
```    96 lemma IdE [elim!]: "p : Id ==> (!!x. p = (x, x) ==> P) ==> P"
```
```    97 by (unfold Id_def) (iprover elim: CollectE)
```
```    98
```
```    99 lemma pair_in_Id_conv [iff]: "((a, b) : Id) = (a = b)"
```
```   100 by (unfold Id_def) blast
```
```   101
```
```   102 lemma reflexive_Id: "reflexive Id"
```
```   103 by (simp add: refl_def)
```
```   104
```
```   105 lemma antisym_Id: "antisym Id"
```
```   106   -- {* A strange result, since @{text Id} is also symmetric. *}
```
```   107 by (simp add: antisym_def)
```
```   108
```
```   109 lemma sym_Id: "sym Id"
```
```   110 by (simp add: sym_def)
```
```   111
```
```   112 lemma trans_Id: "trans Id"
```
```   113 by (simp add: trans_def)
```
```   114
```
```   115
```
```   116 subsection {* Diagonal: identity over a set *}
```
```   117
```
```   118 lemma diag_empty [simp]: "diag {} = {}"
```
```   119 by (simp add: diag_def)
```
```   120
```
```   121 lemma diag_eqI: "a = b ==> a : A ==> (a, b) : diag A"
```
```   122 by (simp add: diag_def)
```
```   123
```
```   124 lemma diagI [intro!,noatp]: "a : A ==> (a, a) : diag A"
```
```   125 by (rule diag_eqI) (rule refl)
```
```   126
```
```   127 lemma diagE [elim!]:
```
```   128   "c : diag A ==> (!!x. x : A ==> c = (x, x) ==> P) ==> P"
```
```   129   -- {* The general elimination rule. *}
```
```   130 by (unfold diag_def) (iprover elim!: UN_E singletonE)
```
```   131
```
```   132 lemma diag_iff: "((x, y) : diag A) = (x = y & x : A)"
```
```   133 by blast
```
```   134
```
```   135 lemma diag_subset_Times: "diag A \<subseteq> A \<times> A"
```
```   136 by blast
```
```   137
```
```   138
```
```   139 subsection {* Composition of two relations *}
```
```   140
```
```   141 lemma rel_compI [intro]:
```
```   142   "(a, b) : s ==> (b, c) : r ==> (a, c) : r O s"
```
```   143 by (unfold rel_comp_def) blast
```
```   144
```
```   145 lemma rel_compE [elim!]: "xz : r O s ==>
```
```   146   (!!x y z. xz = (x, z) ==> (x, y) : s ==> (y, z) : r  ==> P) ==> P"
```
```   147 by (unfold rel_comp_def) (iprover elim!: CollectE splitE exE conjE)
```
```   148
```
```   149 lemma rel_compEpair:
```
```   150   "(a, c) : r O s ==> (!!y. (a, y) : s ==> (y, c) : r ==> P) ==> P"
```
```   151 by (iprover elim: rel_compE Pair_inject ssubst)
```
```   152
```
```   153 lemma R_O_Id [simp]: "R O Id = R"
```
```   154 by fast
```
```   155
```
```   156 lemma Id_O_R [simp]: "Id O R = R"
```
```   157 by fast
```
```   158
```
```   159 lemma rel_comp_empty1[simp]: "{} O R = {}"
```
```   160 by blast
```
```   161
```
```   162 lemma rel_comp_empty2[simp]: "R O {} = {}"
```
```   163 by blast
```
```   164
```
```   165 lemma O_assoc: "(R O S) O T = R O (S O T)"
```
```   166 by blast
```
```   167
```
```   168 lemma trans_O_subset: "trans r ==> r O r \<subseteq> r"
```
```   169 by (unfold trans_def) blast
```
```   170
```
```   171 lemma rel_comp_mono: "r' \<subseteq> r ==> s' \<subseteq> s ==> (r' O s') \<subseteq> (r O s)"
```
```   172 by blast
```
```   173
```
```   174 lemma rel_comp_subset_Sigma:
```
```   175     "s \<subseteq> A \<times> B ==> r \<subseteq> B \<times> C ==> (r O s) \<subseteq> A \<times> C"
```
```   176 by blast
```
```   177
```
```   178 lemma rel_comp_distrib[simp]: "R O (S \<union> T) = (R O S) \<union> (R O T)"
```
```   179 by auto
```
```   180
```
```   181 lemma rel_comp_distrib2[simp]: "(S \<union> T) O R = (S O R) \<union> (T O R)"
```
```   182 by auto
```
```   183
```
```   184
```
```   185 subsection {* Reflexivity *}
```
```   186
```
```   187 lemma reflI: "r \<subseteq> A \<times> A ==> (!!x. x : A ==> (x, x) : r) ==> refl A r"
```
```   188 by (unfold refl_def) (iprover intro!: ballI)
```
```   189
```
```   190 lemma reflD: "refl A r ==> a : A ==> (a, a) : r"
```
```   191 by (unfold refl_def) blast
```
```   192
```
```   193 lemma reflD1: "refl A r ==> (x, y) : r ==> x : A"
```
```   194 by (unfold refl_def) blast
```
```   195
```
```   196 lemma reflD2: "refl A r ==> (x, y) : r ==> y : A"
```
```   197 by (unfold refl_def) blast
```
```   198
```
```   199 lemma refl_Int: "refl A r ==> refl B s ==> refl (A \<inter> B) (r \<inter> s)"
```
```   200 by (unfold refl_def) blast
```
```   201
```
```   202 lemma refl_Un: "refl A r ==> refl B s ==> refl (A \<union> B) (r \<union> s)"
```
```   203 by (unfold refl_def) blast
```
```   204
```
```   205 lemma refl_INTER:
```
```   206   "ALL x:S. refl (A x) (r x) ==> refl (INTER S A) (INTER S r)"
```
```   207 by (unfold refl_def) fast
```
```   208
```
```   209 lemma refl_UNION:
```
```   210   "ALL x:S. refl (A x) (r x) \<Longrightarrow> refl (UNION S A) (UNION S r)"
```
```   211 by (unfold refl_def) blast
```
```   212
```
```   213 lemma refl_empty[simp]: "refl {} {}"
```
```   214 by(simp add:refl_def)
```
```   215
```
```   216 lemma refl_diag: "refl A (diag A)"
```
```   217 by (rule reflI [OF diag_subset_Times diagI])
```
```   218
```
```   219
```
```   220 subsection {* Antisymmetry *}
```
```   221
```
```   222 lemma antisymI:
```
```   223   "(!!x y. (x, y) : r ==> (y, x) : r ==> x=y) ==> antisym r"
```
```   224 by (unfold antisym_def) iprover
```
```   225
```
```   226 lemma antisymD: "antisym r ==> (a, b) : r ==> (b, a) : r ==> a = b"
```
```   227 by (unfold antisym_def) iprover
```
```   228
```
```   229 lemma antisym_subset: "r \<subseteq> s ==> antisym s ==> antisym r"
```
```   230 by (unfold antisym_def) blast
```
```   231
```
```   232 lemma antisym_empty [simp]: "antisym {}"
```
```   233 by (unfold antisym_def) blast
```
```   234
```
```   235 lemma antisym_diag [simp]: "antisym (diag A)"
```
```   236 by (unfold antisym_def) blast
```
```   237
```
```   238
```
```   239 subsection {* Symmetry *}
```
```   240
```
```   241 lemma symI: "(!!a b. (a, b) : r ==> (b, a) : r) ==> sym r"
```
```   242 by (unfold sym_def) iprover
```
```   243
```
```   244 lemma symD: "sym r ==> (a, b) : r ==> (b, a) : r"
```
```   245 by (unfold sym_def, blast)
```
```   246
```
```   247 lemma sym_Int: "sym r ==> sym s ==> sym (r \<inter> s)"
```
```   248 by (fast intro: symI dest: symD)
```
```   249
```
```   250 lemma sym_Un: "sym r ==> sym s ==> sym (r \<union> s)"
```
```   251 by (fast intro: symI dest: symD)
```
```   252
```
```   253 lemma sym_INTER: "ALL x:S. sym (r x) ==> sym (INTER S r)"
```
```   254 by (fast intro: symI dest: symD)
```
```   255
```
```   256 lemma sym_UNION: "ALL x:S. sym (r x) ==> sym (UNION S r)"
```
```   257 by (fast intro: symI dest: symD)
```
```   258
```
```   259 lemma sym_diag [simp]: "sym (diag A)"
```
```   260 by (rule symI) clarify
```
```   261
```
```   262
```
```   263 subsection {* Transitivity *}
```
```   264
```
```   265 lemma transI:
```
```   266   "(!!x y z. (x, y) : r ==> (y, z) : r ==> (x, z) : r) ==> trans r"
```
```   267 by (unfold trans_def) iprover
```
```   268
```
```   269 lemma transD: "trans r ==> (a, b) : r ==> (b, c) : r ==> (a, c) : r"
```
```   270 by (unfold trans_def) iprover
```
```   271
```
```   272 lemma trans_Int: "trans r ==> trans s ==> trans (r \<inter> s)"
```
```   273 by (fast intro: transI elim: transD)
```
```   274
```
```   275 lemma trans_INTER: "ALL x:S. trans (r x) ==> trans (INTER S r)"
```
```   276 by (fast intro: transI elim: transD)
```
```   277
```
```   278 lemma trans_diag [simp]: "trans (diag A)"
```
```   279 by (fast intro: transI elim: transD)
```
```   280
```
```   281 lemma trans_diff_Id: " trans r \<Longrightarrow> antisym r \<Longrightarrow> trans (r-Id)"
```
```   282 unfolding antisym_def trans_def by blast
```
```   283
```
```   284 subsection {* Irreflexivity *}
```
```   285
```
```   286 lemma irrefl_diff_Id[simp]: "irrefl(r-Id)"
```
```   287 by(simp add:irrefl_def)
```
```   288
```
```   289 subsection {* Totality *}
```
```   290
```
```   291 lemma total_on_empty[simp]: "total_on {} r"
```
```   292 by(simp add:total_on_def)
```
```   293
```
```   294 lemma total_on_diff_Id[simp]: "total_on A (r-Id) = total_on A r"
```
```   295 by(simp add: total_on_def)
```
```   296
```
```   297 subsection {* Converse *}
```
```   298
```
```   299 lemma converse_iff [iff]: "((a,b): r^-1) = ((b,a) : r)"
```
```   300 by (simp add: converse_def)
```
```   301
```
```   302 lemma converseI[sym]: "(a, b) : r ==> (b, a) : r^-1"
```
```   303 by (simp add: converse_def)
```
```   304
```
```   305 lemma converseD[sym]: "(a,b) : r^-1 ==> (b, a) : r"
```
```   306 by (simp add: converse_def)
```
```   307
```
```   308 lemma converseE [elim!]:
```
```   309   "yx : r^-1 ==> (!!x y. yx = (y, x) ==> (x, y) : r ==> P) ==> P"
```
```   310     -- {* More general than @{text converseD}, as it ``splits'' the member of the relation. *}
```
```   311 by (unfold converse_def) (iprover elim!: CollectE splitE bexE)
```
```   312
```
```   313 lemma converse_converse [simp]: "(r^-1)^-1 = r"
```
```   314 by (unfold converse_def) blast
```
```   315
```
```   316 lemma converse_rel_comp: "(r O s)^-1 = s^-1 O r^-1"
```
```   317 by blast
```
```   318
```
```   319 lemma converse_Int: "(r \<inter> s)^-1 = r^-1 \<inter> s^-1"
```
```   320 by blast
```
```   321
```
```   322 lemma converse_Un: "(r \<union> s)^-1 = r^-1 \<union> s^-1"
```
```   323 by blast
```
```   324
```
```   325 lemma converse_INTER: "(INTER S r)^-1 = (INT x:S. (r x)^-1)"
```
```   326 by fast
```
```   327
```
```   328 lemma converse_UNION: "(UNION S r)^-1 = (UN x:S. (r x)^-1)"
```
```   329 by blast
```
```   330
```
```   331 lemma converse_Id [simp]: "Id^-1 = Id"
```
```   332 by blast
```
```   333
```
```   334 lemma converse_diag [simp]: "(diag A)^-1 = diag A"
```
```   335 by blast
```
```   336
```
```   337 lemma refl_converse [simp]: "refl A (converse r) = refl A r"
```
```   338 by (unfold refl_def) auto
```
```   339
```
```   340 lemma sym_converse [simp]: "sym (converse r) = sym r"
```
```   341 by (unfold sym_def) blast
```
```   342
```
```   343 lemma antisym_converse [simp]: "antisym (converse r) = antisym r"
```
```   344 by (unfold antisym_def) blast
```
```   345
```
```   346 lemma trans_converse [simp]: "trans (converse r) = trans r"
```
```   347 by (unfold trans_def) blast
```
```   348
```
```   349 lemma sym_conv_converse_eq: "sym r = (r^-1 = r)"
```
```   350 by (unfold sym_def) fast
```
```   351
```
```   352 lemma sym_Un_converse: "sym (r \<union> r^-1)"
```
```   353 by (unfold sym_def) blast
```
```   354
```
```   355 lemma sym_Int_converse: "sym (r \<inter> r^-1)"
```
```   356 by (unfold sym_def) blast
```
```   357
```
```   358 lemma total_on_converse[simp]: "total_on A (r^-1) = total_on A r"
```
```   359 by (auto simp: total_on_def)
```
```   360
```
```   361
```
```   362 subsection {* Domain *}
```
```   363
```
```   364 declare Domain_def [noatp]
```
```   365
```
```   366 lemma Domain_iff: "(a : Domain r) = (EX y. (a, y) : r)"
```
```   367 by (unfold Domain_def) blast
```
```   368
```
```   369 lemma DomainI [intro]: "(a, b) : r ==> a : Domain r"
```
```   370 by (iprover intro!: iffD2 [OF Domain_iff])
```
```   371
```
```   372 lemma DomainE [elim!]:
```
```   373   "a : Domain r ==> (!!y. (a, y) : r ==> P) ==> P"
```
```   374 by (iprover dest!: iffD1 [OF Domain_iff])
```
```   375
```
```   376 lemma Domain_empty [simp]: "Domain {} = {}"
```
```   377 by blast
```
```   378
```
```   379 lemma Domain_insert: "Domain (insert (a, b) r) = insert a (Domain r)"
```
```   380 by blast
```
```   381
```
```   382 lemma Domain_Id [simp]: "Domain Id = UNIV"
```
```   383 by blast
```
```   384
```
```   385 lemma Domain_diag [simp]: "Domain (diag A) = A"
```
```   386 by blast
```
```   387
```
```   388 lemma Domain_Un_eq: "Domain(A \<union> B) = Domain(A) \<union> Domain(B)"
```
```   389 by blast
```
```   390
```
```   391 lemma Domain_Int_subset: "Domain(A \<inter> B) \<subseteq> Domain(A) \<inter> Domain(B)"
```
```   392 by blast
```
```   393
```
```   394 lemma Domain_Diff_subset: "Domain(A) - Domain(B) \<subseteq> Domain(A - B)"
```
```   395 by blast
```
```   396
```
```   397 lemma Domain_Union: "Domain (Union S) = (\<Union>A\<in>S. Domain A)"
```
```   398 by blast
```
```   399
```
```   400 lemma Domain_converse[simp]: "Domain(r^-1) = Range r"
```
```   401 by(auto simp:Range_def)
```
```   402
```
```   403 lemma Domain_mono: "r \<subseteq> s ==> Domain r \<subseteq> Domain s"
```
```   404 by blast
```
```   405
```
```   406 lemma fst_eq_Domain: "fst ` R = Domain R";
```
```   407 by (auto intro!:image_eqI)
```
```   408
```
```   409 lemma Domain_dprod [simp]: "Domain (dprod r s) = uprod (Domain r) (Domain s)"
```
```   410 by auto
```
```   411
```
```   412 lemma Domain_dsum [simp]: "Domain (dsum r s) = usum (Domain r) (Domain s)"
```
```   413 by auto
```
```   414
```
```   415
```
```   416 subsection {* Range *}
```
```   417
```
```   418 lemma Range_iff: "(a : Range r) = (EX y. (y, a) : r)"
```
```   419 by (simp add: Domain_def Range_def)
```
```   420
```
```   421 lemma RangeI [intro]: "(a, b) : r ==> b : Range r"
```
```   422 by (unfold Range_def) (iprover intro!: converseI DomainI)
```
```   423
```
```   424 lemma RangeE [elim!]: "b : Range r ==> (!!x. (x, b) : r ==> P) ==> P"
```
```   425 by (unfold Range_def) (iprover elim!: DomainE dest!: converseD)
```
```   426
```
```   427 lemma Range_empty [simp]: "Range {} = {}"
```
```   428 by blast
```
```   429
```
```   430 lemma Range_insert: "Range (insert (a, b) r) = insert b (Range r)"
```
```   431 by blast
```
```   432
```
```   433 lemma Range_Id [simp]: "Range Id = UNIV"
```
```   434 by blast
```
```   435
```
```   436 lemma Range_diag [simp]: "Range (diag A) = A"
```
```   437 by auto
```
```   438
```
```   439 lemma Range_Un_eq: "Range(A \<union> B) = Range(A) \<union> Range(B)"
```
```   440 by blast
```
```   441
```
```   442 lemma Range_Int_subset: "Range(A \<inter> B) \<subseteq> Range(A) \<inter> Range(B)"
```
```   443 by blast
```
```   444
```
```   445 lemma Range_Diff_subset: "Range(A) - Range(B) \<subseteq> Range(A - B)"
```
```   446 by blast
```
```   447
```
```   448 lemma Range_Union: "Range (Union S) = (\<Union>A\<in>S. Range A)"
```
```   449 by blast
```
```   450
```
```   451 lemma Range_converse[simp]: "Range(r^-1) = Domain r"
```
```   452 by blast
```
```   453
```
```   454 lemma snd_eq_Range: "snd ` R = Range R";
```
```   455 by (auto intro!:image_eqI)
```
```   456
```
```   457
```
```   458 subsection {* Field *}
```
```   459
```
```   460 lemma mono_Field: "r \<subseteq> s \<Longrightarrow> Field r \<subseteq> Field s"
```
```   461 by(auto simp:Field_def Domain_def Range_def)
```
```   462
```
```   463 lemma Field_empty[simp]: "Field {} = {}"
```
```   464 by(auto simp:Field_def)
```
```   465
```
```   466 lemma Field_insert[simp]: "Field (insert (a,b) r) = {a,b} \<union> Field r"
```
```   467 by(auto simp:Field_def)
```
```   468
```
```   469 lemma Field_Un[simp]: "Field (r \<union> s) = Field r \<union> Field s"
```
```   470 by(auto simp:Field_def)
```
```   471
```
```   472 lemma Field_Union[simp]: "Field (\<Union>R) = \<Union>(Field ` R)"
```
```   473 by(auto simp:Field_def)
```
```   474
```
```   475 lemma Field_converse[simp]: "Field(r^-1) = Field r"
```
```   476 by(auto simp:Field_def)
```
```   477
```
```   478
```
```   479 subsection {* Image of a set under a relation *}
```
```   480
```
```   481 declare Image_def [noatp]
```
```   482
```
```   483 lemma Image_iff: "(b : r``A) = (EX x:A. (x, b) : r)"
```
```   484 by (simp add: Image_def)
```
```   485
```
```   486 lemma Image_singleton: "r``{a} = {b. (a, b) : r}"
```
```   487 by (simp add: Image_def)
```
```   488
```
```   489 lemma Image_singleton_iff [iff]: "(b : r``{a}) = ((a, b) : r)"
```
```   490 by (rule Image_iff [THEN trans]) simp
```
```   491
```
```   492 lemma ImageI [intro,noatp]: "(a, b) : r ==> a : A ==> b : r``A"
```
```   493 by (unfold Image_def) blast
```
```   494
```
```   495 lemma ImageE [elim!]:
```
```   496     "b : r `` A ==> (!!x. (x, b) : r ==> x : A ==> P) ==> P"
```
```   497 by (unfold Image_def) (iprover elim!: CollectE bexE)
```
```   498
```
```   499 lemma rev_ImageI: "a : A ==> (a, b) : r ==> b : r `` A"
```
```   500   -- {* This version's more effective when we already have the required @{text a} *}
```
```   501 by blast
```
```   502
```
```   503 lemma Image_empty [simp]: "R``{} = {}"
```
```   504 by blast
```
```   505
```
```   506 lemma Image_Id [simp]: "Id `` A = A"
```
```   507 by blast
```
```   508
```
```   509 lemma Image_diag [simp]: "diag A `` B = A \<inter> B"
```
```   510 by blast
```
```   511
```
```   512 lemma Image_Int_subset: "R `` (A \<inter> B) \<subseteq> R `` A \<inter> R `` B"
```
```   513 by blast
```
```   514
```
```   515 lemma Image_Int_eq:
```
```   516      "single_valued (converse R) ==> R `` (A \<inter> B) = R `` A \<inter> R `` B"
```
```   517 by (simp add: single_valued_def, blast)
```
```   518
```
```   519 lemma Image_Un: "R `` (A \<union> B) = R `` A \<union> R `` B"
```
```   520 by blast
```
```   521
```
```   522 lemma Un_Image: "(R \<union> S) `` A = R `` A \<union> S `` A"
```
```   523 by blast
```
```   524
```
```   525 lemma Image_subset: "r \<subseteq> A \<times> B ==> r``C \<subseteq> B"
```
```   526 by (iprover intro!: subsetI elim!: ImageE dest!: subsetD SigmaD2)
```
```   527
```
```   528 lemma Image_eq_UN: "r``B = (\<Union>y\<in> B. r``{y})"
```
```   529   -- {* NOT suitable for rewriting *}
```
```   530 by blast
```
```   531
```
```   532 lemma Image_mono: "r' \<subseteq> r ==> A' \<subseteq> A ==> (r' `` A') \<subseteq> (r `` A)"
```
```   533 by blast
```
```   534
```
```   535 lemma Image_UN: "(r `` (UNION A B)) = (\<Union>x\<in>A. r `` (B x))"
```
```   536 by blast
```
```   537
```
```   538 lemma Image_INT_subset: "(r `` INTER A B) \<subseteq> (\<Inter>x\<in>A. r `` (B x))"
```
```   539 by blast
```
```   540
```
```   541 text{*Converse inclusion requires some assumptions*}
```
```   542 lemma Image_INT_eq:
```
```   543      "[|single_valued (r\<inverse>); A\<noteq>{}|] ==> r `` INTER A B = (\<Inter>x\<in>A. r `` B x)"
```
```   544 apply (rule equalityI)
```
```   545  apply (rule Image_INT_subset)
```
```   546 apply  (simp add: single_valued_def, blast)
```
```   547 done
```
```   548
```
```   549 lemma Image_subset_eq: "(r``A \<subseteq> B) = (A \<subseteq> - ((r^-1) `` (-B)))"
```
```   550 by blast
```
```   551
```
```   552
```
```   553 subsection {* Single valued relations *}
```
```   554
```
```   555 lemma single_valuedI:
```
```   556   "ALL x y. (x,y):r --> (ALL z. (x,z):r --> y=z) ==> single_valued r"
```
```   557 by (unfold single_valued_def)
```
```   558
```
```   559 lemma single_valuedD:
```
```   560   "single_valued r ==> (x, y) : r ==> (x, z) : r ==> y = z"
```
```   561 by (simp add: single_valued_def)
```
```   562
```
```   563 lemma single_valued_rel_comp:
```
```   564   "single_valued r ==> single_valued s ==> single_valued (r O s)"
```
```   565 by (unfold single_valued_def) blast
```
```   566
```
```   567 lemma single_valued_subset:
```
```   568   "r \<subseteq> s ==> single_valued s ==> single_valued r"
```
```   569 by (unfold single_valued_def) blast
```
```   570
```
```   571 lemma single_valued_Id [simp]: "single_valued Id"
```
```   572 by (unfold single_valued_def) blast
```
```   573
```
```   574 lemma single_valued_diag [simp]: "single_valued (diag A)"
```
```   575 by (unfold single_valued_def) blast
```
```   576
```
```   577
```
```   578 subsection {* Graphs given by @{text Collect} *}
```
```   579
```
```   580 lemma Domain_Collect_split [simp]: "Domain{(x,y). P x y} = {x. EX y. P x y}"
```
```   581 by auto
```
```   582
```
```   583 lemma Range_Collect_split [simp]: "Range{(x,y). P x y} = {y. EX x. P x y}"
```
```   584 by auto
```
```   585
```
```   586 lemma Image_Collect_split [simp]: "{(x,y). P x y} `` A = {y. EX x:A. P x y}"
```
```   587 by auto
```
```   588
```
```   589
```
```   590 subsection {* Inverse image *}
```
```   591
```
```   592 lemma sym_inv_image: "sym r ==> sym (inv_image r f)"
```
```   593 by (unfold sym_def inv_image_def) blast
```
```   594
```
```   595 lemma trans_inv_image: "trans r ==> trans (inv_image r f)"
```
```   596   apply (unfold trans_def inv_image_def)
```
```   597   apply (simp (no_asm))
```
```   598   apply blast
```
```   599   done
```
```   600
```
```   601
```
```   602 subsection {* Finiteness *}
```
```   603
```
```   604 lemma finite_converse [iff]: "finite (r^-1) = finite r"
```
```   605   apply (subgoal_tac "r^-1 = (%(x,y). (y,x))`r")
```
```   606    apply simp
```
```   607    apply (rule iffI)
```
```   608     apply (erule finite_imageD [unfolded inj_on_def])
```
```   609     apply (simp split add: split_split)
```
```   610    apply (erule finite_imageI)
```
```   611   apply (simp add: converse_def image_def, auto)
```
```   612   apply (rule bexI)
```
```   613    prefer 2 apply assumption
```
```   614   apply simp
```
```   615   done
```
```   616
```
```   617 text {* \paragraph{Finiteness of transitive closure} (Thanks to Sidi
```
```   618 Ehmety) *}
```
```   619
```
```   620 lemma finite_Field: "finite r ==> finite (Field r)"
```
```   621   -- {* A finite relation has a finite field (@{text "= domain \<union> range"}. *}
```
```   622   apply (induct set: finite)
```
```   623    apply (auto simp add: Field_def Domain_insert Range_insert)
```
```   624   done
```
```   625
```
```   626
```
```   627 subsection {* Version of @{text lfp_induct} for binary relations *}
```
```   628
```
```   629 lemmas lfp_induct2 =
```
```   630   lfp_induct_set [of "(a, b)", split_format (complete)]
```
```   631
```
```   632 end
```