diff --git a/moo/kernel/Apex.moo b/moo/kernel/Apex.moo
index 757aac7..6dec859 100644
--- a/moo/kernel/Apex.moo
+++ b/moo/kernel/Apex.moo
@@ -215,10 +215,15 @@ extend Apex
 	{
 		| c |
 		c := self superclass.
-		[c notNil] whileTrue: [
+		(* [c notNil] whileTrue: [
 			[ c == aClass ] ifTrue: [^true].
 			c := c superclass.
-		].
+		]. *)
+		while (c notNil)
+		{
+			if (c == aClass) { ^true }.
+			c := c superclass.
+		}.
 		^false
 	}
 
@@ -233,6 +238,7 @@ extend Apex
 
 	method(#class) isKindOf: aClass
 	{
+		<primitive: #_is_kind_of>
 		^(self isMemberOf: aClass) or: [self inheritsFrom: aClass].
 	}
 
@@ -243,6 +249,7 @@ extend Apex
 
 	method isKindOf: aClass
 	{
+		<primitive: #_is_kind_of>
 		^(self isMemberOf: aClass) or: [self class inheritsFrom: aClass].
 	}
 
diff --git a/moo/kernel/Context.moo b/moo/kernel/Context.moo
index 603c83b..b7cbae4 100644
--- a/moo/kernel/Context.moo
+++ b/moo/kernel/Context.moo
@@ -42,7 +42,7 @@ block context...
 ---------------------------------- *)
 }
 
-class(#pointer) MethodContext(Context)
+class(#pointer,#final,#limited) MethodContext(Context)
 {
 	var method, receiver, home, origin.
 
@@ -99,7 +99,7 @@ class(#pointer) MethodContext(Context)
 	}
 }
 
-class(#pointer) BlockContext(Context)
+class(#pointer,#final,#limited) BlockContext(Context)
 {
 	var nargs, source, home, origin.
 
diff --git a/moo/kernel/Process.moo b/moo/kernel/Process.moo
index 3031053..9c80d6f 100644
--- a/moo/kernel/Process.moo
+++ b/moo/kernel/Process.moo
@@ -94,12 +94,14 @@ TODO: timed wait...
 	}
 *)
 
+	(* TODO: MIGRATE TO MUTEX...
 	method critical: aBlock
 	{
 		self wait.
 		^aBlock ensure: [ self signal ]
-	}
+	}*)
 
+	
 	## ==================================================================
 
 	method heapIndex
@@ -133,6 +135,26 @@ TODO: timed wait...
 	}
 }
 
+class Mutex(Semaphore)
+{
+	method(#class) new
+	{
+		| s |
+		s := super new.
+		s signal.
+		^s.
+	}
+
+	method lock  { ^self wait }
+	method unlock { ^self signal }
+
+	method critical: block
+	{
+		self wait.
+		^block ensure: [ self signal ]
+	}
+}
+
  
 (*
  xxx := Semaphore new.
diff --git a/moo/kernel/test-001.moo b/moo/kernel/test-001.moo
index e24464c..844491f 100644
--- a/moo/kernel/test-001.moo
+++ b/moo/kernel/test-001.moo
@@ -1,5 +1,7 @@
-## TODO: use this file as a regress testing source.
-##       rename it to test-001.moo and use it as a test case file.
+##
+## TEST CASES for namespacing
+##
+
 #include 'Moo.moo'.
 
 
diff --git a/moo/kernel/test-003.moo b/moo/kernel/test-003.moo
index 3e1e93c..c5962fd 100644
--- a/moo/kernel/test-003.moo
+++ b/moo/kernel/test-003.moo
@@ -1,3 +1,6 @@
+##
+## TEST CASES for basic methods
+##
 
 #include 'Moo.moo'.
 
@@ -50,8 +53,30 @@ class MyObject(TestObject)
 
 	method(#class) main
 	{
-		'START OF MAIN' dump.
-		'EDN OF MAIN' dump.
-	}
+		| tc limit |
+		
+		tc := %(
+			## 0 - 4
+			[(Object isKindOf: Class) == true],
+			[(Object isKindOf: Apex) == true],
+			[(Class isKindOf: Class) == true],
+			[(Class isKindOf: Apex) == true],
+			[(Class isKindOf: Object) == false],
 
+			[(Apex isKindOf: Class) == true],
+			[(SmallInteger isKindOf: Integer) == false],
+			[(10 isKindOf: Integer) == true],
+
+			[(Apex isMemberOf: Class) == true],
+			[(Class isMemberOf: Class) == true]
+		).
+
+		limit := tc size.
+
+		0 priorTo: limit by: 1 do: [ :idx |
+			| tb |
+			tb := tc at: idx.
+			System log(System.Log.INFO, idx asString, (if (tb value) { ' PASS' } else { ' FAIL' }), S'\n').
+		]
+	}
 }
diff --git a/moo/lib/exec.c b/moo/lib/exec.c
index d89ab01..fc54073 100644
--- a/moo/lib/exec.c
+++ b/moo/lib/exec.c
@@ -2098,6 +2098,27 @@ static moo_pfrc_t pf_hash (moo_t* moo, moo_ooi_t nargs)
 	return MOO_PF_SUCCESS;
 }
 
+static moo_pfrc_t pf_is_kind_of (moo_t* moo, moo_ooi_t nargs)
+{
+	moo_oop_t rcv, _class;
+
+	rcv = MOO_STACK_GETRCV(moo, nargs);
+	_class = MOO_STACK_GETARG(moo, nargs, 0);
+
+	MOO_PF_CHECK_ARGS (moo, nargs, MOO_CLASSOF(moo, _class) == moo->_class);
+
+	if (moo_iskindof(moo, rcv, (moo_oop_class_t)_class))
+	{
+		MOO_STACK_SETRET (moo, nargs, moo->_true);
+	}
+	else
+	{
+		MOO_STACK_SETRET (moo, nargs, moo->_false);
+	}
+
+	return MOO_PF_SUCCESS;
+}
+
 static moo_pfrc_t pf_responds_to (moo_t* moo, moo_ooi_t nargs)
 {
 	moo_oop_t rcv, selector;
@@ -4135,6 +4156,7 @@ static pf_t pftab[] =
 
 	{ "_hash",                                 { pf_hash,                                 0, 0 } },
 
+	{ "_is_kind_of",                           { pf_is_kind_of,                           1, 1, } },
 	{ "_responds_to",                          { pf_responds_to,                          1, 1  } },
 	{ "_perform",                              { pf_perform,                              1, MA } },
 
diff --git a/moo/lib/gc.c b/moo/lib/gc.c
index ac40a59..26af327 100644
--- a/moo/lib/gc.c
+++ b/moo/lib/gc.c
@@ -224,7 +224,7 @@ static kernel_class_info_t kernel_classes[] =
 
 	{ 13,
 	  { 'M','e','t','h','o','d','C','o','n','t','e','x','t' },
-	  0,
+	  MOO_CLASS_SELFSPEC_FLAG_FINAL | MOO_CLASS_SELFSPEC_FLAG_LIMITED,
 	  MOO_CONTEXT_NAMED_INSTVARS,
 	  MOO_CLASS_SPEC_FLAG_INDEXED,
 	  MOO_OBJ_TYPE_OOP,
@@ -232,7 +232,7 @@ static kernel_class_info_t kernel_classes[] =
 
 	{ 12,
 	  { 'B','l','o','c','k','C','o','n','t','e','x','t' },
-	  0,
+	  MOO_CLASS_SELFSPEC_FLAG_FINAL | MOO_CLASS_SELFSPEC_FLAG_LIMITED,
 	  MOO_CONTEXT_NAMED_INSTVARS,
 	  MOO_CLASS_SPEC_FLAG_INDEXED,
 	  MOO_OBJ_TYPE_OOP,
diff --git a/moo/lib/moo.c b/moo/lib/moo.c
index f8d7be1..29adb76 100644
--- a/moo/lib/moo.c
+++ b/moo/lib/moo.c
@@ -973,3 +973,27 @@ moo_oop_t moo_findclass (moo_t* moo, moo_oop_nsdic_t nsdic, const moo_ooch_t* na
 
 	return ass->value;
 }
+
+int moo_iskindof (moo_t* moo, moo_oop_t obj, moo_oop_class_t _class)
+{
+	moo_oop_class_t c;
+
+	c = MOO_CLASSOF(moo,obj); /* c := self class */
+	if (c == moo->_class) 
+	{
+		/* object is a class */
+		if (_class == moo->_class) return 1; 
+	}
+	else
+	{
+		if (c == _class) return 1; 
+	}
+
+	c = (moo_oop_class_t)c->superclass;
+	while ((moo_oop_t)c != moo->_nil)
+	{
+		if (c == _class) return 1;
+		c = (moo_oop_class_t)c->superclass;
+	}
+	return 0;
+}
diff --git a/moo/lib/moo.h b/moo/lib/moo.h
index 43cec1b..2ca74bd 100644
--- a/moo/lib/moo.h
+++ b/moo/lib/moo.h
@@ -1729,6 +1729,12 @@ MOO_EXPORT moo_oop_t moo_findclass (
 	const moo_ooch_t* name
 );
 
+MOO_EXPORT int moo_iskindof (
+	moo_t*          moo,
+	moo_oop_t       obj,
+	moo_oop_class_t _class
+);
+
 /* =========================================================================
  * TRAILER MANAGEMENT
  * ========================================================================= */