--- /dev/null
+(**************************************************************************)
+(* ___ *)
+(* ||M|| *)
+(* ||A|| A project by Andrea Asperti *)
+(* ||T|| *)
+(* ||I|| Developers: *)
+(* ||T|| The HELM team. *)
+(* ||A|| http://helm.cs.unibo.it *)
+(* \ / *)
+(* \ / This file is distributed under the terms of the *)
+(* v GNU General Public License Version 2 *)
+(* *)
+(**************************************************************************)
+
+include "o-concrete_spaces.ma".
+
+definition btop_carr: BTop → Type ≝ λo:BTop. carr (carrbt o).
+
+coercion btop_carr.
+
+definition btop_carr': BTop → setoid ≝ λo:BTop. carrbt o.
+
+coercion btop_carr'.
+
+definition downarrow: ∀S:BTop. unary_morphism (Ω \sup S) (Ω \sup S).
+ intros; constructor 1;
+ [ apply (λU:Ω \sup S.{a | ∃b:carrbt S. b ∈ U ∧ a ∈ A ? (singleton ? b)});
+ intros; simplify; split; intro; cases H1; cases x; exists [1,3: apply w]
+ split; try assumption; [ apply (. H‡#) | apply (. H \sup -1‡#) ] assumption
+ | intros; split; intros 2; cases f; exists; [1,3: apply w] cases x; split;
+ try assumption; [ apply (. #‡H) | apply (. #‡H \sup -1)] assumption]
+qed.
+
+interpretation "downarrow" 'downarrow a = (fun_1 __ (downarrow _) a).
+
+definition ffintersects: ∀S:BTop. binary_morphism1 (Ω \sup S) (Ω \sup S) (Ω \sup S).
+ intros; constructor 1;
+ [ apply (λU,V. ↓U ∩ ↓V);
+ | intros; apply (.= (†H)‡(†H1)); apply refl1]
+qed.
+
+interpretation "ffintersects" 'fintersects U V = (fun1 ___ (ffintersects _) U V).
+
+record formal_topology: Type ≝
+ { bt:> BTop;
+ converges: ∀U,V: Ω \sup bt. A ? (U ↓ V) = A ? U ∩ A ? V
+ }.
+
+definition bt': formal_topology → basic_topology ≝ λo:formal_topology.bt o.
+
+coercion bt'.
+
+definition ffintersects': ∀S:BTop. binary_morphism1 S S (Ω \sup S).
+ intros; constructor 1;
+ [ apply (λb,c:S. (singleton S b) ↓ (singleton S c));
+ | intros; apply (.= (†H)‡(†H1)); apply refl1]
+qed.
+
+interpretation "ffintersects'" 'fintersects U V = (fun1 ___ (ffintersects' _) U V).
+
+record formal_map (S,T: formal_topology) : Type ≝
+ { cr:> continuous_relation_setoid S T;
+ C1: ∀b,c. extS ?? cr (b ↓ c) = ext ?? cr b ↓ ext ?? cr c;
+ C2: extS ?? cr T = S
+ }.
+
+definition cr': ∀FT1,FT2.formal_map FT1 FT2 → continuous_relation FT1 FT2 ≝
+ λFT1,FT2,c. cr FT1 FT2 c.
+
+coercion cr'.
+
+definition formal_map_setoid: formal_topology → formal_topology → setoid1.
+ intros (S T); constructor 1;
+ [ apply (formal_map S T);
+ | constructor 1;
+ [ apply (λf,f1: formal_map S T.f=f1);
+ | simplify; intros 1; apply refl1
+ | simplify; intros 2; apply sym1
+ | simplify; intros 3; apply trans1]]
+qed.
+
+definition cr'': ∀FT1,FT2.formal_map_setoid FT1 FT2 → arrows1 BTop FT1 FT2 ≝
+ λFT1,FT2,c.cr ?? c.
+
+coercion cr''.
+
+definition cr''': ∀FT1,FT2.formal_map_setoid FT1 FT2 → arrows1 REL FT1 FT2 ≝
+ λFT1,FT2:formal_topology.λc:formal_map_setoid FT1 FT2.cont_rel FT1 FT2 (cr' ?? c).
+
+coercion cr'''.
+
+axiom C1':
+ ∀S,T: formal_topology.∀f:formal_map_setoid S T.∀U,V: Ω \sup T.
+ extS ?? f (U ↓ V) = extS ?? f U ↓ extS ?? f V.
+
+definition formal_map_composition:
+ ∀o1,o2,o3: formal_topology.
+ binary_morphism1
+ (formal_map_setoid o1 o2)
+ (formal_map_setoid o2 o3)
+ (formal_map_setoid o1 o3).
+ intros; constructor 1;
+ [ intros; whd in c c1; constructor 1;
+ [ apply (comp1 BTop ??? c c1);
+ | intros;
+ apply (.= (extS_com ??? c c1 ?));
+ apply (.= †(C1 ?????));
+ apply (.= (C1' ?????));
+ apply (.= ((†((extS_singleton ????) \sup -1))‡(†((extS_singleton ????) \sup -1))));
+ apply (.= (extS_com ??????)\sup -1 ‡ (extS_com ??????) \sup -1);
+ apply (.= (extS_singleton ????)‡(extS_singleton ????));
+ apply refl1;
+ | apply (.= (extS_com ??? c c1 ?));
+ apply (.= (†(C2 ???)));
+ apply (.= (C2 ???));
+ apply refl1;]
+ | intros; simplify;
+ change with (comp1 BTop ??? a b = comp1 BTop ??? a' b');
+ apply prop1; assumption]
+qed.
+