diff --git a/diff.js b/diff.js
index 9dd367b..1b9f318 100644
--- a/diff.js
+++ b/diff.js
@@ -694,20 +694,36 @@ object.makeConstructor('IN', Object.assign(Object.create(LogicType.prototype), {
 
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 
 // AT(A, K) == L iff A in L and L[K] == A
+//
+// NOTE: this also supports path keys -- i.e. array of path elements that
+// 		will be traversed and the last one checked...
+// NOTE: to include an array as an explicit key (Map/...) wrap it in 
+// 		an array:
+// 			AT([[123]], ...)
+//
 // XXX .key can't be a pattern at this point...
-// XXX this is a potential problem as with a pattern key we would need to
-// 		look ahead to pick the correct candidate...
+// 		...to implement this we would need to do:
+// 			1) a search for a matching pattern...
+// 			2) handle multiple matches in some manner (first, all?)...
 // XXX this falls into recursion on:
 // 		X = AT('moo')
 // 		X.value = OR(123, X)
 // 		cmp(X, {'moo', 333})
 // 			...this would also break on checking a recursive structure against 
 // 			a recursive pattern...
+// XXX support Maps, ...
 var AT = 
 module.AT = 
 object.makeConstructor('AT', Object.assign(Object.create(LogicType.prototype), {
 	__cmp__: function(obj, cmp, context){
-		if(cmp(obj != null ? obj[this.key] : null, this.value, context)){
+		var key = this.key instanceof Array ? this.key : [this.key]
+		var no_result = {}
+		obj = key
+			.reduce(function(o, k){
+				return (o == null || o === no_result) ? 
+					no_result 
+					: o[k] }, obj)
+		if(obj !== no_result && cmp(obj, this.value, context)){
 			return true
 		}
 		return false
diff --git a/format.js b/format.js
index ccedf8a..ac620d0 100644
--- a/format.js
+++ b/format.js
@@ -34,9 +34,8 @@ var {
 
 var VALUE =
 module.VALUE = OR(
-	// XXX use these taken from .placeholders...
-	OR(EMPTY, LIKE('EMPTY')),
-	OR(NONE, LIKE('NONE')),
+	OR(LIKE('EMPTY'), EMPTY),
+	OR(LIKE('NONE'), NONE),
 	ANY)
 
 
@@ -54,8 +53,6 @@ module.SIDE_VALUES = OR(
 var CHANGE =
 module.CHANGE = AND(
 	AT('path', L),
-	// XXX optional...
-	// 		...see DIFF_OBJECT's options for description...
 	AT('type', OR(S, undefined)),
 	SIDE_VALUES)
 
@@ -69,6 +66,7 @@ module.DIFF_FLAT = OR(
 //---------------------------------------------------------------------
 // Tree diff...
 
+// Basic...
 var BASIC_CHANGE =
 module.BASIC_CHANGE = AND(
 	AT('type', 'Basic'),
@@ -76,6 +74,7 @@ module.BASIC_CHANGE = AND(
 
 
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 
+// Object...
 var OBJECT_ITEM =
 module.OBJECT_ITEM = OR(
 	[S, DIFF_TREE],
@@ -90,6 +89,7 @@ module.OBJECT_CHANGE = AND(
 
 
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 
+// Array...
 var ARRAY_ITEM =
 module.ARRAY_ITEM = OR(
 	[ANY, ANY, DIFF_TREE],
@@ -100,8 +100,8 @@ module.ARRAY_ITEMS = AND(
 	AT('length', OR(
 		[N, N], 
 		undefined)),
-	AT('items', L(
-		OR(
+	AT('items', 
+		L(OR(
 			ARRAY_ITEM,
 			OBJECT_ITEM))),
 	// XXX
@@ -109,18 +109,20 @@ module.ARRAY_ITEMS = AND(
 
 var ARRAY_CHANGE =
 module.ARRAY_CHANGE = AND(
-		AT('type', 'Array'),
-		ARRAY_ITEMS)
+	AT('type', 'Array'),
+	ARRAY_ITEMS)
 
 
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 
+// Text...
 var TEXT_CHANGE =
 module.TEXT_CHANGE = AND(
-		AT('type', 'Text'),
-		ARRAY_ITEMS)
+	AT('type', 'Text'),
+	ARRAY_ITEMS)
 
-// XXX it makes sense to make this a recursive pattern...
-// 		...need to check if we stop on a recursive pattern...
+
+// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 
+// XXX need to check if we stop on a recursive pattern...
 // XXX TEST!!!
 var DIFF_TREE =
 module.DIFF_TREE = OR(
@@ -142,20 +144,22 @@ module.DIFF_OBJECT = AND(
 	AT('version', diff.FORMAT_VERSION),
 
 	// instance metadata...
-	AT('options', AND(
- 		AT('tree_diff', OR(B, NULL)),
- 		AT('keep_none', OR(B, NULL)),
- 		AT('min_text_length', OR(N, NULL)),
-		AT('no_attributes', OR(B, NULL)),
- 		AT('NONE', OR(ANY, NULL)),
- 		AT('EMPTY', OR(ANY, NULL)),
- 		AT('no_length', OR(B, NULL)),
- 		AT('cmp', OR(F, NULL)) )),
-	AT('placeholders', AND(
-		AT('NONE', 
-			VAR('NONE', ANY)),
-		AT('EMPTY', 
-			VAR('EMPTY', ANY)))),
+	AT('options', 
+		AND(
+			AT('tree_diff', OR(B, NULL)),
+			AT('keep_none', OR(B, NULL)),
+			AT('min_text_length', OR(N, NULL)),
+			AT('no_attributes', OR(B, NULL)),
+			AT('NONE', OR(ANY, NULL)),
+			AT('EMPTY', OR(ANY, NULL)),
+			AT('no_length', OR(B, NULL)),
+			AT('cmp', OR(F, NULL)) )),
+	AT('placeholders', 
+		AND(
+			AT('NONE', 
+				VAR('NONE', ANY)),
+			AT('EMPTY', 
+				VAR('EMPTY', ANY)))),
 	AT('timestamp', N),
 
 	// diff...