diff --git a/lib/versioning/merge.js b/lib/versioning/merge.js
index 7ef70ba..ae80a03 100644
--- a/lib/versioning/merge.js
+++ b/lib/versioning/merge.js
@@ -1,5 +1,5 @@
-import { emptySet, add, length, forEach, union, has } from "../structures/set.js";
-import { getDepth, Slot, Value, Write } from "./value_slot.js";
+import { emptySet, add, length, forEach, has, remove } from "../structures/set.js";
+import { getDepth, Slot } from "./value_slot.js";
 import { compareSlot } from "./compare.js";
 import { makeTypeParser } from "../parser/type_parser.js";
 import { newDynamic } from "../primitives/dynamic.js";
@@ -20,6 +20,10 @@ export const findLCA = slotA => slotB => {
   }
 };
 
+// returns
+//  {slotA} if slotA is younger
+//  {slotB} if slotB is younger
+//  {slotA, slotB} if they are concurrent (conflicting)
 export const merge = slotA => slotB => {
   const lca = findLCA(slotA)(slotB);
   if (compareSlot(lca)(slotA) === 0) {
@@ -34,7 +38,7 @@ export const merge = slotA => slotB => {
 };
 
 export const mergeN = slots => {
-  let toDelete = emptySetOfSlots;
+  let result = slots;
   forEach(slots)(slotA => {
     forEach(slots)(slotB => {
       // compare all non-identical pairs
@@ -44,26 +48,18 @@ export const mergeN = slots => {
           // if in the pair, one is an ancestor of the other,
           // only keep the other
           if (has(m)(slotA)) {
-            toDelete = add(toDelete)(slotB);
+            result = remove(result)(slotB);
           }
         }
       }
     });
   });
-  let result = emptySetOfSlots;
-  forEach(slots)(slot => {
-    if (!has(toDelete)(slot)) {
-      result = add(result)(slot);
-    }
-  })
   return result;
 };
 
 const mkType = makeTypeParser({
   extraPrimitives: [
-    ["Value", Value],
-    ["Slot" , Slot ],
-    ["Write", Write],
+    ["Slot" , Slot],
   ],
 });
 
diff --git a/lib/versioning/value_slot.js b/lib/versioning/value_slot.js
index 3784ae8..dbbc64d 100644
--- a/lib/versioning/value_slot.js
+++ b/lib/versioning/value_slot.js
@@ -20,8 +20,8 @@ const [
   [, {i: matchValue}],
 ] = makeModuleEnum(Value)([
   {l: "literal"  , r: Dynamic},
-  {l: "read"     , r: Write}, // a 'read' reads the result of a Write
-  {l: "transform", r: Transformation},
+  {l: "read"     , r: Write}, // <- a 'read' reads the result of a Write (to a Slot)
+  {l: "transform", r: Transformation}, // <- result of a function call
 ]);
 
 // Enum: Slot
@@ -36,7 +36,7 @@ const [
   {l: "write", r: Write},
 ]);
 
-// Struct: Transformation
+// Struct: Transformation (i.e., a function call)
 const [
   // constructor
   [, {i: newTransformation}],
@@ -45,9 +45,9 @@ const [
   // [, {i: getFn}],
   // [, {i: getOutput}],
 ] = makeModuleStruct(Transformation)([
-  {l: "input" , r: Value  },
-  {l: "fn"    , r: Value  },
-  {l: "output", r: Dynamic},
+  {l: "input" , r: Value  }, // <- the input is a value (e.g., could be the result of a Transformation itself)
+  {l: "fn"    , r: Value  }, // <- the function is also a value (e.g., could also be result of a transformation, e.g., when currying)
+  {l: "output", r: Dynamic}, // <- the result
 ]);
 
 // Struct: Write