diff --git a/compare/registry.js b/compare/registry.js
index 9852e01..dc2342e 100644
--- a/compare/registry.js
+++ b/compare/registry.js
@@ -1,3 +1,4 @@
+import { getInst, getType } from "../primitives/dynamic.js";
 import { SymbolBool, SymbolChar, SymbolDouble, SymbolInt, SymbolType, SymbolUnit } from "../primitives/types.js";
 import { symbolList, symbolProduct, symbolSet, symbolSum } from "../structures/types.js";
 import { compareBools, compareNumbers, compareStrings, compareUnits } from "./primitives.js";
@@ -17,11 +18,15 @@ const typeSymbolToCmp = new Map([
   [symbolProduct, compareProducts],
   [symbolSum    , compareSums],
   [symbolSet    , compareSets],
-])
+]);
 
 export const makeCompareFn = type => {
   return type.params.reduce(
     (acc, cur) => acc(makeCompareFn(cur)),
     typeSymbolToCmp.get(type.symbol)
   );
-}
+};
+
+export const compareDynamic = x => y =>
+  compareTypes(getType(x))(getType(y))
+    || makeCompareFn(getType(x))(getInst(x))(getInst(y));
diff --git a/compare/structures.js b/compare/structures.js
index d1f669d..dbb9a9f 100644
--- a/compare/structures.js
+++ b/compare/structures.js
@@ -3,7 +3,7 @@
 import { compareNumbers } from "./primitives.js"
 import { get, length as lengthLs } from "../structures/list.js";
 import { read, length as lengthSet } from "../structures/set.js";
-import { constructorProduct, getLeft, getRight } from "../structures/product.js";
+import { newProduct, getLeft, getRight } from "../structures/product.js";
 import { match } from "../structures/sum.js";
 
 // (a -> a -> Int) -> [a] -> [a] -> Int
@@ -28,12 +28,12 @@ export const compareProducts = compareLeft => compareRight => x => y => {
 
 // (a -> a -> Int) -> (b -> b -> Int) -> (a | b) -> (a | b) -> Int
 export const compareSums = compareLeft => compareRight => x => y => {
-  return match(x)(constructorProduct
-    (leftValueX => match(y)(constructorProduct
+  return match(x)(newProduct
+    (leftValueX => match(y)(newProduct
       (leftValueY => compareLeft(leftValueX)(leftValueY))
       ((rightValueY) => -1) // x is 'left' and y is 'right' => x < y
     ))
-    (rightValueX => match(y)(constructorProduct
+    (rightValueX => match(y)(newProduct
       (leftValueY => 1) // x is 'right' and y is 'left' => x > y
       (rightValueY => compareRight(rightValueX)(rightValueY))
     ))
diff --git a/examples/enum.js b/examples/enum.js
index ff5e16c..c6231e2 100644
--- a/examples/enum.js
+++ b/examples/enum.js
@@ -2,13 +2,13 @@ import { makeCompareFn } from "../compare/registry.js";
 import { Int, Unit } from "../primitives/types.js";
 import { unit } from "../primitives/unit.js";
 import { enumType, makeConstructors, makeMatchFn } from "../structures/enum.js";
-import { constructorProduct } from "../structures/product.js";
+import { newProduct } from "../structures/product.js";
 import { lsType, prettyT } from "../structures/types.js";
 
 const variants = [
-  constructorProduct("price")(Int),
-  constructorProduct("prices")(lsType(Int)),
-  constructorProduct("not_found")(Unit),
+  newProduct("price")(Int),
+  newProduct("prices")(lsType(Int)),
+  newProduct("not_found")(Unit),
 ];
 
 const myEnumType = enumType(variants);
diff --git a/examples/int_or_bool.js b/examples/int_or_bool.js
index 0a1e1f0..9b29e79 100644
--- a/examples/int_or_bool.js
+++ b/examples/int_or_bool.js
@@ -1,6 +1,6 @@
 import { assign, makeGeneric, unify } from "../generics/generics.js";
 import { Bool, Int } from "../primitives/types.js";
-import { constructorLeft, constructorRight, match } from "../structures/sum.js";
+import { newLeft, newRight, match } from "../structures/sum.js";
 import { fnType, sumType } from "../structures/types.js";
 import { pretty } from '../util/pretty.js';
 
@@ -33,7 +33,7 @@ console.log(assign(
   makeGeneric(() => IntOrBool),
 ));
 
-console.log("calling constructorLeft with Int:");
+console.log("calling newLeft with Int:");
 const typeAtCallSite = assign(
   makeGeneric((a, b) =>
     fnType
@@ -51,10 +51,10 @@ console.log(pretty(assign(
 )));
 
 console.log("valid function calls:");
-console.log(cipFunction(constructorLeft(5)));
-console.log(cipFunction(constructorLeft(7)));
-console.log(cipFunction(constructorRight(true)));
+console.log(cipFunction(newLeft(5)));
+console.log(cipFunction(newLeft(7)));
+console.log(cipFunction(newRight(true)));
 
 console.log("invalid function calls:");
 console.log(cipFunction(5));
-console.log(cipFunction(constructorLeft("abc")));
+console.log(cipFunction(newLeft("abc")));
diff --git a/examples/main.js b/examples/prompt.js
similarity index 100%
rename from examples/main.js
rename to examples/prompt.js
diff --git a/lib/point_structural.js b/lib/point_structural.js
index c162c74..cf866a0 100644
--- a/lib/point_structural.js
+++ b/lib/point_structural.js
@@ -1,17 +1,17 @@
 import { prettyT, typedFnType } from "../structures/types.js"
 import { Double } from "../primitives/types.js";
 import { makeConstructor, makeConstructorType, makeGetters, makeGettersTypes, structType } from "../structures/struct.js";
-import { constructorProduct } from "../structures/product.js";
+import { newProduct } from "../structures/product.js";
 import { makeTypeConstructor } from "../type_constructor.js";
 
 const cartFields = [
-  constructorProduct("x")(Double),
-  constructorProduct("y")(Double),
+  newProduct("x")(Double),
+  newProduct("y")(Double),
 ];
 
 const polarFields = [
-  constructorProduct("r")(Double),
-  constructorProduct("θ")(Double),
+  newProduct("r")(Double),
+  newProduct("θ")(Double),
 ];
 
 // Nominal types:
diff --git a/primitives/dynamic.js b/primitives/dynamic.js
new file mode 100644
index 0000000..769470b
--- /dev/null
+++ b/primitives/dynamic.js
@@ -0,0 +1,19 @@
+import { typedFnType } from "../structures/types.js";
+import { Any, Type } from "./types.js";
+import { makeTypeConstructor } from "../type_constructor.js";
+
+// A type-link, connecting a value to its Type.
+export const symbolDynamic = Symbol('Dynamic');
+export const Dynamic = makeTypeConstructor(symbolDynamic)(0);
+
+export const getInst = lnk => lnk.i;
+export const getType = lnk => lnk.t;
+
+export const ModuleDynamic = {l:[
+  {i: Dynamic, t: Type},
+  {i: Any    , t: Type},
+
+  ...typedFnType(getInst, fnType => fnType(Dynamic)(Any)),
+  ...typedFnType(getType, fnType => fnType(Dynamic)(Any)),
+]};
+
diff --git a/primitives/generic_type.js b/primitives/generic_type.js
index c9a0065..111505f 100644
--- a/primitives/generic_type.js
+++ b/primitives/generic_type.js
@@ -1,4 +1,4 @@
-import { constructorLeft, constructorRight } from "../structures/sum.js";
+import { newLeft, newRight } from "../structures/sum.js";
 import { setType, sumType, typedFnType } from "../structures/types.js";
 import { Any, GenericType, SymbolT, Type, Unit } from "./types.js";
 import { unit } from "./unit.js";
@@ -7,8 +7,8 @@ export const getType     = genericType => genericType.type;
 export const getTypeVars = genericType => genericType.typeVars;
 
 export const toNonGeneric = genericType => (genericType.typeVars.size === 0)
-  ? constructorRight(genericType.type)
-  : constructorLeft(unit);
+  ? newRight(genericType.type)
+  : newLeft(unit);
 
 export const ModuleGenericType = {l:[
   {i: GenericType, t: Any},
diff --git a/stdlib.js b/stdlib.js
index 9f6c1bf..0c5e726 100644
--- a/stdlib.js
+++ b/stdlib.js
@@ -12,14 +12,14 @@ import { ModuleList } from "./structures/list.js";
 import { ModuleProduct } from "./structures/product.js";
 import { ModuleSum } from "./structures/sum.js";
 import { ModuleType } from "./primitives/type.js";
-import { ModuleTyped } from "./typed.js";
+import { ModuleDynamic } from "./primitives/dynamic.js";
 import { ModuleSet } from "./structures/set.js";
 import { ModuleGenericType } from "./primitives/generic_type.js";
 
 export const ModuleStd = {l:[
   ...ModuleType.l,
   ...ModuleGenericType.l,
-  ...ModuleTyped.l,
+  ...ModuleDynamic.l,
 
   ...ModuleTypeConstructor.l,
   ...ModuleSymbols.l,
diff --git a/structures/enum.js b/structures/enum.js
index d8c7786..34d74c6 100644
--- a/structures/enum.js
+++ b/structures/enum.js
@@ -1,7 +1,7 @@
 import { Bottom } from "../primitives/types.js";
 import { capitalizeFirstLetter } from "../util/util.js";
-import { constructorProduct, getLeft, getRight } from "./product.js";
-import { constructorLeft, constructorRight, match } from "./sum.js";
+import { newProduct as newProduct, getLeft, getRight } from "./product.js";
+import { newLeft, newRight, match } from "./sum.js";
 import { sumType } from "./types.js";
 
 // 'variants' is an array of (name: string, type: Type) pairs.
@@ -34,7 +34,7 @@ export const makeMatchFn = variants => {
   const [_, ...remainingVariants] = variants;
   return sum => handler => {
     return (
-      match(sum)(constructorProduct
+      match(sum)(newProduct
         (leftValue => eatParameters(remainingVariants.length, handler(leftValue)))
         (rightValue => makeMatchFn(remainingVariants)(rightValue))
       ));
@@ -48,10 +48,10 @@ export const makeConstructors = variants => {
   const [variant, ...remainingVariants] = variants;
   const name = getLeft(variant);
   const ctorName = `new${capitalizeFirstLetter(name)}`;
-  const constructor = { [ctorName]: val => constructorLeft(val) }[ctorName];
+  const constructor = { [ctorName]: val => newLeft(val) }[ctorName];
   return [
     constructor,
     ...makeConstructors(remainingVariants).map(ctor =>
-      ({[ctor.name]: val => constructorRight(ctor(val))}[ctor.name])),
+      ({[ctor.name]: val => newRight(ctor(val))}[ctor.name])),
   ];
 }
diff --git a/structures/list.js b/structures/list.js
index d06eca5..2d409db 100644
--- a/structures/list.js
+++ b/structures/list.js
@@ -1,9 +1,9 @@
-import { fnType, typedFnType } from "./types.js";
+import { typedFnType } from "./types.js";
 import { Char, GenericType, Type } from "../primitives/types.js";
 import { Int } from "../primitives/types.js";
 import { makeGeneric } from "../generics/generics.js";
 import { lsType } from "./types.js";
-import { Typed } from "../typed.js"
+import { Dynamic } from "../primitives/dynamic.js"
 
 // 'normal' implementation
 export const emptyList = {l:[]};
@@ -22,7 +22,7 @@ export const fold = ls => callback => initial => {
 }
 
 export const String = lsType(Char); // alias
-export const Module = lsType(Typed);
+export const Module = lsType(Dynamic);
 
 export const ModuleList = {l:[
   // Type -> Type
diff --git a/structures/product.js b/structures/product.js
index af65c09..b66cb9e 100644
--- a/structures/product.js
+++ b/structures/product.js
@@ -9,7 +9,7 @@ import { typedFnType } from "./types.js";
 import { prodType } from "./types.js";
 
 // In JS, all products are encoded in the same way:
-export const constructorProduct = l => r => ({l, r});
+export const newProduct = l => r => ({l, r});
 export const getLeft     = product => product.l;
 export const getRight    = product => product.r;
 
@@ -26,7 +26,7 @@ export const ModuleProduct = {l: [
   ),
 
   // a -> b -> (a, b)
-  ...typedFnType(constructorProduct, fnType =>
+  ...typedFnType(newProduct, fnType =>
     makeGeneric((a, b) =>
       fnType
         (a)
diff --git a/structures/struct.js b/structures/struct.js
index 649d54c..fa43919 100644
--- a/structures/struct.js
+++ b/structures/struct.js
@@ -1,7 +1,7 @@
 import { Unit } from "../primitives/types.js";
 import { unit } from "../primitives/unit.js";
 import { capitalizeFirstLetter } from "../util/util.js";
-import { constructorProduct, getLeft, getRight } from "./product.js";
+import { newProduct, getLeft, getRight } from "./product.js";
 import { fnType, prodType } from "./types.js";
 
 // 'fields' is an array of (name: string, type: Type) pairs.
@@ -26,7 +26,7 @@ export const makeConstructor = fields => {
     return nextParam => {
       const wrappedName = 'wrapped_' + ret.name;
       const newRet = {
-        [wrappedName]: inner => constructorProduct(nextParam)(ret(inner)),
+        [wrappedName]: inner => newProduct(nextParam)(ret(inner)),
       }[wrappedName];
       return internal(nParams-1, newRet);
     }
diff --git a/structures/sum.js b/structures/sum.js
index 274588f..197f38d 100644
--- a/structures/sum.js
+++ b/structures/sum.js
@@ -8,8 +8,8 @@ import { typedFnType } from "./types.js";
 import { makeGeneric } from "../generics/generics.js";
 import { sumType } from "./types.js";
 
-export const constructorLeft  = left  => ({t: "L", v: left }); // 't': tag, 'v': value
-export const constructorRight = right => ({t: "R", v: right});
+export const newLeft  = left  => ({t: "L", v: left }); // 't': tag, 'v': value
+export const newRight = right => ({t: "R", v: right});
 
 // signature:
 //   sum-type -> (leftType -> resultType, rightType -> resultType) -> resultType
@@ -31,7 +31,7 @@ export const ModuleSum = {l:[
     ),
 
   // a -> a | b
-  ...typedFnType(constructorLeft, fnType =>
+  ...typedFnType(newLeft, fnType =>
     makeGeneric((a, b) =>
       fnType
         (a)
@@ -39,7 +39,7 @@ export const ModuleSum = {l:[
     ), GenericType),
 
   // b -> a | b
-  ...typedFnType(constructorRight, fnType =>
+  ...typedFnType(newRight, fnType =>
     makeGeneric((a, b) =>
       fnType
         (b)
diff --git a/typed.js b/typed.js
deleted file mode 100644
index b3a1d71..0000000
--- a/typed.js
+++ /dev/null
@@ -1,18 +0,0 @@
-import { typedFnType } from "./structures/types.js";
-import { Any, Type } from "./primitives/types.js";
-import { makeTypeConstructor } from "./type_constructor.js";
-
-// A type-link, connecting a value to its Type.
-const symbolTyped = Symbol('Typed');
-export const Typed = makeTypeConstructor(symbolTyped)(0);
-
-const getInst = lnk => lnk.i;
-const getType = lnk => lnk.t;
-
-export const ModuleTyped = {l:[
-  {i: Typed, t: Type},
-  {i: Any  , t: Type},
-
-  ...typedFnType(getInst, fnType => fnType(Typed)(Any)),
-  ...typedFnType(getType, fnType => fnType(Typed)(Any)),
-]};
diff --git a/versioning/types.js b/versioning/types.js
new file mode 100644
index 0000000..8068653
--- /dev/null
+++ b/versioning/types.js
@@ -0,0 +1,26 @@
+import { Dynamic } from "../primitives/dynamic.js";
+import { Int } from "../primitives/types.js";
+import { enumType } from "../structures/enum.js";
+import { newProduct } from "../structures/product.js";
+import { structType } from "../structures/struct.js";
+import { prettyT, prodType } from "../structures/types.js";
+
+const Slot = structType([
+  newProduct("value")(() => Value),
+  newProduct("depth")(() => Int),
+  newProduct("overwrites")(() => Slot),
+]);
+
+// A Value is either:
+//   - a literal, without any dependencies.
+//   - read from a slot. the Value then has a read-dependency on that slot.
+//   - a transformation of another Value, by a function. the function is also a Value.
+const variants = [
+  newProduct("literal", () => Dynamic),
+  newProduct("read", () => Slot),
+  newProduct("transformation", () => prodType(Value, Dynamic)),
+];
+const Value = enumType(variants);
+
+// console.log(prettyT(Slot));
+// console.log(prettyT(Value));
\ No newline at end of file