diff --git a/lib/feature_extractor.js b/lib/feature_extractor.js
index 157556b7..0e927bc1 100644
--- a/lib/feature_extractor.js
+++ b/lib/feature_extractor.js
@@ -135,41 +135,65 @@ function extractFeatures(code, file, print_ast, features, skip_minified) {
 
 /* -----[ functions ]----- */
 
-function nodeToString(node, parent) {
+function Property(must_infer, name, annotation) {
+	this.must_infer = must_infer;
+	this.name = name;
+	this.annotation = annotation;
+}
+
+Property.prototype.toString = function () {
+	return (this.must_infer ? INFER : GIVEN) + this.name;
+}
+
+function nodeToProperty(node, parent) {
 	if (node == null) return null;
 
 	if (node instanceof AST_Symbol){
 		if (node instanceof AST_This ){
-			return GIVEN + node.name;
+			//return GIVEN + node.name;
+			return new Property(false, node.name, "");
 		}
 		// AST_Symbol::unmangleable() returns true if this symbol cannot be renamed (it's either global, undeclared, or defined in scope where eval or with are in use.
 		if (node.unmangleable()){
-			return GIVEN + node.name;
+			//return GIVEN + node.name;
+			return new Property(false, node.name, "");
 		}		
-		return INFER + node.definition().id + "-" + node.name;		
+		//return INFER + node.definition().id + "-" + node.name;
+		return new Property(true, node.definition().id + "-" + node.name, "");
 	} else if (node instanceof AST_Constant){
-		return GIVEN + "!" + nodeType(node) + "!" + String(node.value).slice(0,64);
+		//var name = GIVEN + String(node.value).slice(0,64);
+		//name.annotation = "!" + nodeType(node) + "!";
+		//return name;
+		return new Property(false, String(node.value).slice(0,64), nodeType(node));
 	} else if (node instanceof AST_Sub){
 		//x[1], x -> expression, 1 -> property
-		return (nodeToString(node.expression, node) != null) ? nodeToString(node.expression, node) + "[]" : null;
+
+		if (nodeToProperty(node.expression, node) == null) {
+			return null;
+		}
+		var prop = nodeToProperty(node.expression, node);
+		prop.annotation += "[]";
+		return prop;
 	} else if (node instanceof AST_PropAccess){
-		return GIVEN + node.property;
+		//return GIVEN + node.property;
+		return new Property(false, node.property, "");
 	} else if (node instanceof AST_Defun) {
 		//function foo(...) { ... }		
-		return nodeToString(node.name, node);
+		return nodeToProperty(node.name, node);
 	} else if (node instanceof AST_VarDef){
 		// var x = function () { ... }
-		return nodeToString(node.name, node);
+		return nodeToProperty(node.name, node);
 	} else if (node instanceof AST_Assign){
 		//x = function () { ... }
-		return nodeToString(node.left, node);
+		return nodeToProperty(node.left, node);
 	} else if (node instanceof AST_ObjectProperty){
 		// { "x" : function () { ... } }
-		return GIVEN + node.key;	
+		//return GIVEN + node.key;
+		return new Property(false, node.key, "");
 	} else if (node instanceof AST_Call){
 		//x.foo( function () { ... } )
 		//foo( function () { ... } )
-		return nodeToString(node.expression,  node);
+		return nodeToProperty(node.expression,  node);
 	} else if (node instanceof AST_Lambda) {
 		if (node.parent instanceof AST_Call){
 			//'node.parent.expression != node' as lambda can call itself
@@ -177,10 +201,19 @@ function nodeToString(node, parent) {
 				return null;
 			}
 
-			return (nodeToString(node.parent.expression, node) != null) ? nodeToString(node.parent.expression, node)  + "(" + node.child_id + ")" : null;
+			if (nodeToProperty(node.parent.expression, node) == null) {
+				return null;
+			}
+
+			//var name = nodeToProperty(node.parent.expression, node);
+			//name.annotation = "(" + node.child_id + ")";
+			//return name;
+			var prop = nodeToProperty(node.parent.expression, node);
+			prop.annotation += "(" + node.child_id + ")";
+			return prop;
 		}
 		if (node.parent != parent) {
-			return nodeToString(node.parent, node);
+			return nodeToProperty(node.parent, node);
 		}
 	}
 
@@ -245,7 +278,7 @@ function printAst(toplevel){
 
 function generateAstFeatures(toplevel, feature_outputter) {
 	var walker = new TreeWalker(function(node){
-		// console.log(nodeType(node) + " - " + nodeToString(node));
+		// console.log(nodeType(node) + " - " + nodeToProperty(node));
 		var paths = this.node_finder.find(node);
 		for (var i = 0; i < paths.length; i++) {
 			var path1 = paths[i];
@@ -267,8 +300,8 @@ function generateAstFeatures(toplevel, feature_outputter) {
 				}
 
 				feature_outputter.addFeature(
-					nodeToString(node1), 
-					nodeToString(node2),
+					nodeToProperty(node1),
+					nodeToProperty(node2),
 					//pathToStringBw(path1, common_prefix_len) + ":" + nodeType(path1[common_prefix_len - 1]) + ":" + pathToStringFw(path2, common_prefix_len)
 					(path2.length != common_prefix_len)
 						? pathToStringBw(path1, common_prefix_len) + ":" + pathToStringFw(path2, common_prefix_len - 1)
@@ -296,20 +329,20 @@ function addFeatures(lhss, lhs_label, rhs, rhs_label, feature_outputter){
 
 function addScopeConstraints(node, toplevel, feature_outputter){
 	feature_outputter.beginScope();
-	var name = nodeToString(node);
+	var name = nodeToProperty(node);
 	if (name != null)
 		feature_outputter.addToScope(name);
 
 	for (var i = 0; i < node.enclosed.length; i++){
-		feature_outputter.addToScope(nodeToString(node.enclosed[i].orig[0]));
+		feature_outputter.addToScope(nodeToProperty(node.enclosed[i].orig[0]));
 	}
 
 	node.variables.each(function(symbol){
-		feature_outputter.addToScope(nodeToString(symbol.orig[0]));
+		feature_outputter.addToScope(nodeToProperty(symbol.orig[0]));
 	});
 
 	toplevel.globals.each(function(symbol){
-		feature_outputter.addToScope(nodeToString(symbol.orig[0]));
+		feature_outputter.addToScope(nodeToProperty(symbol.orig[0]));
 	});
 
 	feature_outputter.endScope();
@@ -330,11 +363,11 @@ function generateFnamesFeatures(toplevel, feature_outputter){
 
 	toplevel.walk(new TreeWalker(function(node, descend){
 
-		if ((node instanceof AST_Defun || node instanceof AST_Lambda) && nodeToString(node) != null) {
-			var name = nodeToString(node);
+		if ((node instanceof AST_Defun || node instanceof AST_Lambda) && nodeToProperty(node) != null) {
+			var name = nodeToProperty(node);
 
 			for (var i = 0; i < node.argnames.length; i++) {
-				addFeatures([name], "FN", nodeToString(node.argnames[i]), "PAR", feature_outputter);
+				addFeatures([name], "FN", nodeToProperty(node.argnames[i]), "PAR", feature_outputter);
 			}
 
 			outer_funcs.push(name);
@@ -345,17 +378,17 @@ function generateFnamesFeatures(toplevel, feature_outputter){
 		}
 
 		if (node instanceof AST_New) {	
-			addFeatures(outer_funcs, "FN", nodeToString(node), "NEW", feature_outputter);
+			addFeatures(outer_funcs, "FN", nodeToProperty(node), "NEW", feature_outputter);
 		} else if (node instanceof AST_Call) {			
-			addFeatures(outer_funcs, "FN", nodeToString(node), "CALL", feature_outputter);
+			addFeatures(outer_funcs, "FN", nodeToProperty(node), "CALL", feature_outputter);
 		} else if (node instanceof AST_Constant){
-			addFeatures(outer_funcs, "FN", nodeToString(node), nodeType(node).toUpperCase(), feature_outputter);
+			addFeatures(outer_funcs, "FN", nodeToProperty(node), nodeType(node).toUpperCase(), feature_outputter);
 		} else if (node instanceof AST_VarDef){
-			addFeatures(outer_funcs, "FN", nodeToString(node.name), "DECL", feature_outputter);
+			addFeatures(outer_funcs, "FN", nodeToProperty(node.name), "DECL", feature_outputter);
 		} else if (node instanceof AST_Dot && !(node.parent instanceof AST_Call)) {			
-			addFeatures(outer_funcs, "FN", nodeToString(node), "PROP", feature_outputter);
-		} else if (node instanceof AST_Return && nodeToString(node.value) != null) {
-			addFeatures(outer_funcs, "FN", nodeToString(node.value), "RETURN", feature_outputter);
+			addFeatures(outer_funcs, "FN", nodeToProperty(node), "PROP", feature_outputter);
+		} else if (node instanceof AST_Return && nodeToProperty(node.value) != null) {
+			addFeatures(outer_funcs, "FN", nodeToProperty(node.value), "RETURN", feature_outputter);
 		}
 	}));
 }
@@ -461,12 +494,20 @@ FeatureJsonOutputter.prototype.addFeature = function(a, b, name){
 	}
 
 	//do not add features between two fixed nodes
-	if (a[0] == GIVEN && b[0] == GIVEN) {		
+	//if (a[0] == GIVEN && b[0] == GIVEN) {
+	if (!a.must_infer && !b.must_infer) {
 		return;
 	}
 
-	var a_id = this.string_map.getId(a);
-	var b_id = this.string_map.getId(b);
+	if (a.annotation != "") {
+		name = a.annotation + "-" + name;
+	}
+	if (b.annotation != "") {
+		name = name + "-" + b.annotation;
+	}
+
+	var a_id = this.string_map.getId(a.toString());
+	var b_id = this.string_map.getId(b.toString());
 
 	if (a_id == b_id || this.visitFeature(a_id, b_id, name)){
 		return;
@@ -563,7 +604,7 @@ StringMap.prototype.hasId = function(input){
 	}
 
 	//we add a special character in from to allow for keys such as "toString"
-	var escaped_input = "#" + input;
+	var escaped_input = "#" + input.toString();
 	return escaped_input in this.map;
 };
 
@@ -572,6 +613,7 @@ StringMap.prototype.getId = function(input){
 		throw new Error("error null");
 	}
 
+	input = input.toString();
 	//we add a special character in from to allow for keys such as "toString"
 	var escaped_input = "#" + input;
 
diff --git a/test/feature_extraction/fnames.js b/test/feature_extraction/fnames.js
index ad9e3637..2d5c7951 100644
--- a/test/feature_extraction/fnames.js
+++ b/test/feature_extraction/fnames.js
@@ -83,14 +83,14 @@ inner_lambda_assign_local: {
 			{"a": 0,	"b": 1,	"f2": "FNPAR"},
 			{"a": 0,	"b": 2,	"f2": "FNDECL"},
 			{"a": 2,	"b": 3,	"f2": "FNCALL"},			
-			{"a": 2,	"b": 4,	"f2": "FNSTRING"}			
+			{"a": 2,	"b": 4,	"f2": "FNSTRING-String"}
 			],
 			"assign":[
 			{"v": 0,	"giv": "chunkData"},
 			{"v": 1,	"inf": "x"},
 			{"v": 2,	"inf": "local"},
 			{"v": 3,	"giv": "log"},
-			{"v": 4,	"giv": "!String!hello"}
+			{"v": 4,	"giv": "hello"}
 			]
 		}'
 	}
@@ -134,10 +134,10 @@ inner_lambda_assign_sub: {
 	expect: {
 		'{
 			"query":[
-			{"a": 0,	"b": 1,	"f2": "FNPAR"}
+			{"a": 0,	"b": 1,	"f2": "[]-FNPAR"}
 			],
 			"assign":[
-			{"v": 0,	"giv": "global%5B%5D"},
+			{"v": 0,	"giv": "global"},
 			{"v": 1,	"inf": "a"}
 			]
 		}'
@@ -187,10 +187,10 @@ inner_lambda_arg: {
 	expect: {
 		'{
 			"query":[
-			{"a": 0,	"b": 1,	"f2": "FNPAR"}
+			{"a": 0,	"b": 1,	"f2": "(2)-FNPAR"}
 			],
 			"assign":[
-			{"v": 0,	"giv": "substring(2)"},
+			{"v": 0,	"giv": "substring"},
 			{"v": 1,	"inf": "x"}
 			]
 		}'
@@ -211,10 +211,10 @@ inner_lambda_arg2: {
 	expect: {
 		'{
 			"query":[
-			{"a": 0,	"b": 1,	"f2": "FNPAR"}
+			{"a": 0,	"b": 1,	"f2": "(2)-FNPAR"}
 			],
 			"assign":[
-			{"v": 0,	"giv": "substring(2)"},
+			{"v": 0,	"giv": "substring"},
 			{"v": 1,	"inf": "b"}
 			]
 		}'
diff --git a/test/feature_extraction/general.js b/test/feature_extraction/general.js
index 96f6e0ea..470a3536 100644
--- a/test/feature_extraction/general.js
+++ b/test/feature_extraction/general.js
@@ -10,11 +10,11 @@ truncate_constants: {
 	expect: {
 		'{
 			"query":[
-			{"a": 0,	"b": 1,	"f2": ":VarDef[1]"}
+			{"a": 0,	"b": 1,	"f2": ":VarDef[1]-String"}
 			],
 			"assign":[
 			{"v": 0,	"inf": "x"},
-			{"v": 1,	"giv": "!String!very%20long%20string%2C%20very%20long%20string%2C%20very%20long%20string%2C%20very%20long%20"}
+			{"v": 1,	"giv": "very%20long%20string%2C%20very%20long%20string%2C%20very%20long%20string%2C%20very%20long%20"}
 			]
 		}'
 	}
@@ -32,11 +32,11 @@ escape_constants: {
 	expect: {
 		'{
 			"query":[
-			{"a": 0,	"b": 1,	"f2": ":VarDef[1]"}
+			{"a": 0,	"b": 1,	"f2": ":VarDef[1]-String"}
 			],
 			"assign":[
 			{"v": 0,	"inf": "x"},
-			{"v": 1,	"giv": "!String!%22quoted%20text%22"}
+			{"v": 1,	"giv": "%22quoted%20text%22"}
 			]
 		}'
 	}
@@ -58,8 +58,8 @@ var_scope: {
 	expect: {
 		'{
 			"query":[
-			{"a": 0,	"b": 1,	"f2": ":VarDef[1]"},
-			{"a": 2,	"b": 3,	"f2": ":VarDef[1]"},
+			{"a": 0,	"b": 1,	"f2": ":VarDef[1]-Number"},
+			{"a": 2,	"b": 3,	"f2": ":VarDef[1]-Number"},
 			{"a": 4,	"b": 0,	"f2": ":VarDef[1]Binary+[0]"},
 			{"a": 4,	"b": 2,	"f2": ":VarDef[1]Binary+[1]"},
 			{"a": 0,	"b": 2,	"f2": ":Binary+[1]"},
@@ -68,9 +68,9 @@ var_scope: {
 			],
 			"assign":[
 			{"v": 0,	"inf": "a"},
-			{"v": 1,	"giv": "!Number!1"},
+			{"v": 1,	"giv": "1"},
 			{"v": 2,	"inf": "b"},
-			{"v": 3,	"giv": "!Number!2"},
+			{"v": 3,	"giv": "2"},
 			{"v": 4,	"inf": "x"}
 			]
 		}'
@@ -266,15 +266,15 @@ func_allow_different_features_duplicates: {
 		'{
 			"query":[
 			{"a": 0,	"b": 1,	"f2": ":Dot[0]"},
-			{"a": 0,	"b": 2,	"f2": "Dot[0]:Call[1]"},
-			{"a": 0,	"b": 2,	"f2": "Dot[0]:Call[2]"},
-			{"a": 0,	"b": 2,	"f2": "Dot[0]:Call[3]"},
-			{"a": 0,	"b": 2,	"f2": "Dot[0]:Call[4]"}
+			{"a": 0,	"b": 2,	"f2": "Dot[0]:Call[1]-Number"},
+			{"a": 0,	"b": 2,	"f2": "Dot[0]:Call[2]-Number"},
+			{"a": 0,	"b": 2,	"f2": "Dot[0]:Call[3]-Number"},
+			{"a": 0,	"b": 2,	"f2": "Dot[0]:Call[4]-Number"}
 			],
 			"assign":[
 			{"v": 0,	"inf": "x"},
 			{"v": 1,	"giv": "foo"},
-			{"v": 2,	"giv": "!Number!42"}
+			{"v": 2,	"giv": "42"}
 			]
 		}'
 	}