diff --git a/moo/kernel/Apex.moo b/moo/kernel/Apex.moo
index ee0fb5a..f5476f9 100644
--- a/moo/kernel/Apex.moo
+++ b/moo/kernel/Apex.moo
@@ -4,8 +4,26 @@ class Apex(nil)
 
 class(#limited) Error(Apex)
 {
+	pooldic Code
+	{
+		ENOERR   := #\E0.
+		EGENERIC := #\E1.
+		ENOIMPL  := #\E2.
+		ESYSERR  := #\E3.
+		EINTERN  := #\E4.
+		ESYSMEM  := #\E5.
+		EOOMEM   := #\E6.
+		EINVAL   := #\E7.
+		ENOENT   := #\E8.
+		EPERM    := #\E12.
+		ERANGE   := #\E20.
+
+		ELIMIT  := #\E9999.
+		## add more items...
+	}
 }
 
+(*
 pooldic Error.Code
 {
 	ENOERR   := #\E0.
@@ -21,8 +39,8 @@ pooldic Error.Code
 	ERANGE   := #\E20.
 
 	ELIMIT  := #\E9999.
-(* add more items... *)
-}
+## add more items... 
+} *)
 
 (*pooldic Error.Code2 
 {
diff --git a/moo/kernel/Socket.moo b/moo/kernel/Socket.moo
index 5d9fc5d..8d18d8e 100644
--- a/moo/kernel/Socket.moo
+++ b/moo/kernel/Socket.moo
@@ -231,6 +231,19 @@ class Socket(Object) from 'sck'
 	## the internal representation used by various modules. (e.g. sck)
 	var(#get) handle := -1.
 
+	## TODO: generate these family and type from the C header 
+	pooldic Family
+	{
+		INET := 2.
+		INET6 := 10.
+	}
+
+	pooldic Type
+	{
+		STREAM := 1.
+		DGRAM  := 2.
+	}
+
 	method(#primitive) open(family, type, proto).
 	## map the open primitive again with a different name for strict internal use only.
 	## this method is supposed to be used to handle an accepted socket in server sockets.
@@ -284,19 +297,6 @@ class Socket(Object) from 'sck'
 	}
 }
 
-(* TODO: generate these family and type from the C header *)
-pooldic Socket.Family
-{
-	INET := 2.
-	INET6 := 10.
-}
-
-pooldic Socket.Type
-{
-	STREAM := 1.
-	DGRAM  := 2.
-}
-
 class SyncSocket(Socket)
 {
 	var iosem, tmoutsem, sg.
diff --git a/moo/kernel/System.moo b/moo/kernel/System.moo
index dd85da5..52008c4 100644
--- a/moo/kernel/System.moo
+++ b/moo/kernel/System.moo
@@ -12,6 +12,20 @@ class System(Apex)
 {
 	var(#class) asyncsg.
 
+	pooldic Log
+	{
+		## -----------------------------------------------------------
+		## defines log levels
+		## these items must follow defintions in moo.h
+		## -----------------------------------------------------------
+
+		DEBUG := 1.
+		INFO  := 2.
+		WARN  := 4.
+		ERROR := 8.
+		FATAL := 16.
+	}
+
 	method(#class) addAsyncSemaphore: sem
 	{
 		^self.asyncsg addSemaphore: sem
@@ -124,24 +138,7 @@ class System(Apex)
 		s signalAfterSecs: secs nanosecs: nanosecs.
 		s wait.
 	}
-}
 
-pooldic System.Log
-{
-	## -----------------------------------------------------------
-	## defines log levels
-	## these items must follow defintions in moo.h
-	## -----------------------------------------------------------
-
-	DEBUG := 1.
-	INFO  := 2.
-	WARN  := 4.
-	ERROR := 8.
-	FATAL := 16.
-}
-
-extend System
-{
 	## the following methods may not look suitable to be placed
 	## inside a system dictionary. but they are here for quick and dirty
 	## output production from the moo code.
diff --git a/moo/kernel/X11.moo b/moo/kernel/X11.moo
index 99bdba3..ce78ce1 100644
--- a/moo/kernel/X11.moo
+++ b/moo/kernel/X11.moo
@@ -15,6 +15,38 @@ class X11(Object) from 'x11'
 	var event_loop_sem, event_loop_proc.
 	var llevent_blocks.
 
+	class Exception(System.Exception)
+	{
+	}
+
+	class Point(Object)
+	{
+		var(#get,#set) x := 0, y := 0.
+	}
+
+	class Dimension(Object)
+	{
+		var(#get,#set) width := 0, height := 0.
+	}
+
+	class Rectangle(Object)
+	{
+		var(#get,#set)
+			x      := 0,
+			y      := 0,
+			width  := 0,
+			height := 0.
+	}
+
+	extend Point
+	{
+		method print
+		{
+			x dump.
+			y dump.
+		}
+	}
+
 	method(#primitive,#liberal) _open_display(name).
 	method(#primitive) _close_display.
 	method(#primitive) _get_fd.
@@ -47,29 +79,6 @@ class X11(Object) from 'x11'
 	}
 }
 
-class X11.Exception(System.Exception)
-{
-}
-
-class X11.Point(Object)
-{
-	var(#get,#set) x := 0, y := 0.
-}
-
-class X11.Dimension(Object)
-{
-	var(#get,#set) width := 0, height := 0.
-}
-
-class X11.Rectangle(Object)
-{
-	var(#get,#set)
-		x      := 0,
-		y      := 0,
-		width  := 0,
-		height := 0.
-}
-
 ## ---------------------------------------------------------------------------
 ## Event
 ## ---------------------------------------------------------------------------
diff --git a/moo/lib/comp.c b/moo/lib/comp.c
index 51cefe3..32293da 100644
--- a/moo/lib/comp.c
+++ b/moo/lib/comp.c
@@ -247,6 +247,7 @@ enum voca_id_t
 };
 typedef enum voca_id_t voca_id_t;
 
+static int compile_class_definition (moo_t* moo, int class_type);
 static int compile_pooldic_definition (moo_t* moo);
 static int compile_block_statement (moo_t* moo);
 static int compile_method_statement (moo_t* moo);
@@ -7656,8 +7657,15 @@ static int __compile_class_definition (moo_t* moo, int class_type)
 		return -1;
 	}
 
+	if (cc->cunit_parent && cc->cunit_parent->cunit_type == MOO_CUNIT_CLASS && TOKEN_TYPE(moo) == MOO_IOTOK_IDENT_DOTTED)
+	{
+		/* the name of a nested class cannot be multi-segmented */
+		moo_setsynerrbfmt (moo, MOO_SYNERR_IDENT, TOKEN_LOC(moo), TOKEN_NAME(moo), "undotted identifier expected");
+		return -1;
+	}
+
 #if 0
-	if (TOKEN_TYPE(moo) == MOO_IOTOK_IDENT && is_restricted_word (TOKEN_NAME(moo)))
+	if (TOKEN_TYPE(moo) == MOO_IOTOK_IDENT && is_restricted_word(TOKEN_NAME(moo)))
 	{
 		/* wrong class name */
 		moo_setsynerr (moo, MOO_SYNERR_CLASSNAMEINVAL, TOKEN_LOC(moo), TOKEN_NAME(moo));
@@ -7665,10 +7673,25 @@ static int __compile_class_definition (moo_t* moo, int class_type)
 	}
 #endif
 
-	/* copy the class name */
+	
+	/* [NOTE] TOKEN_NAME(moo) doesn't contain the full name if it's nested 
+	 *        inside a class. it is merely a name that appeared in the source
+	 *        code.
+	 *  TODO: compose the full name by traversing the namespace chain. */
 	if (set_class_fqn(moo, cc, TOKEN_NAME(moo)) <= -1) return -1;
 	cc->fqn_loc = moo->c->tok.loc;
-	if (TOKEN_TYPE(moo) == MOO_IOTOK_IDENT_DOTTED)
+
+	if (cc->cunit_parent && cc->cunit_parent->cunit_type == MOO_CUNIT_CLASS)
+	{
+		moo_cunit_class_t* c = (moo_cunit_class_t*)cc->cunit_parent;
+		if ((moo_oop_t)c->self_oop->nsdic == moo->_nil)
+		{
+			/* attach a new namespace dictionary to the nsdic field of the class */
+			if (!attach_nsdic_to_class(moo, c->self_oop)) return -1;
+		}
+		cc->ns_oop = c->self_oop->nsdic; /* TODO: if c->nsdic is nil, create one? */
+	}
+	else if (TOKEN_TYPE(moo) == MOO_IOTOK_IDENT_DOTTED)
 	{
 		if (preprocess_dotted_name(moo, (class_type == CLASS_TYPE_EXTEND? PDN_DONT_ADD_NS: 0), MOO_NULL, &cc->fqn, &cc->fqn_loc, &cc->name, &cc->ns_oop) <= -1) return -1;
 	}
@@ -7724,8 +7747,7 @@ static int __compile_class_definition (moo_t* moo, int class_type)
 
 		cc->super_oop = cc->self_oop->superclass;
 
-		MOO_ASSERT (moo, cc->super_oop == moo->_nil || 
-		                 MOO_CLASSOF(moo, cc->super_oop) == moo->_class);
+		MOO_ASSERT (moo, cc->super_oop == moo->_nil || MOO_CLASSOF(moo, cc->super_oop) == moo->_class);
 	}
 	else
 	{
@@ -8096,6 +8118,18 @@ static int __compile_class_definition (moo_t* moo, int class_type)
 			GET_TOKEN (moo);
 			if (compile_pooldic_definition(moo) <= -1) return -1;
 		}
+		else if (is_token_word(moo, VOCA_CLASS))
+		{
+			/* class definition nested inside another class definition */
+			GET_TOKEN (moo);
+			if (compile_class_definition(moo, CLASS_TYPE_NORMAL) <= -1) return -1;
+		}
+		else if (is_token_word(moo, VOCA_EXTEND))
+		{
+			/* class extension nested inside another class definition */
+			GET_TOKEN (moo);
+			if (compile_class_definition(moo, CLASS_TYPE_EXTEND) <= -1) return -1;
+		}
 		else break;
 	}
 	while (1);
@@ -8263,10 +8297,14 @@ static int __compile_pooldic_definition (moo_t* moo)
 	if (pd->cunit_parent && pd->cunit_parent->cunit_type == MOO_CUNIT_CLASS && TOKEN_TYPE(moo) == MOO_IOTOK_IDENT_DOTTED)
 	{
 		/* the pool dictionary nested inside a class cannot be multi-segmented */
-		moo_setsynerr (moo, MOO_SYNERR_IDENT, TOKEN_LOC(moo), TOKEN_NAME(moo));
+		moo_setsynerrbfmt (moo, MOO_SYNERR_IDENT, TOKEN_LOC(moo), TOKEN_NAME(moo), "undotted identifier expected");
 		goto oops;
 	}
 
+	/* [NOTE] TOKEN_NAME(moo) doesn't contain the full name if it's nested 
+	 *        inside a class. it is merely a name that appeared in the source
+	 *        code. 
+	 *  TODO: compose the full name by traversing the namespace chain. */
 	if (set_pooldic_fqn(moo, pd, TOKEN_NAME(moo)) <= -1) goto oops;
 	pd->fqn_loc = moo->c->tok.loc;
 
diff --git a/moo/lib/err.c b/moo/lib/err.c
index 21202c4..5e50c50 100644
--- a/moo/lib/err.c
+++ b/moo/lib/err.c
@@ -405,7 +405,19 @@ void moo_setsynerrbfmt (moo_t* moo, moo_synerrnum_t num, const moo_ioloc_t* loc,
 	
 	if (tgt)
 	{
-		moo->c->synerr.tgt = *tgt;
+		if (tgt->len >= MOO_COUNTOF(moo->c->synerr_tgtbuf) && 
+		    moo_copyoocharstosbuf(moo, tgt->ptr, tgt->len, MOO_SBUF_ID_SYNERR) >= 0)
+		{
+			moo->c->synerr.tgt.ptr = moo->sbuf[MOO_SBUF_ID_SYNERR].ptr;
+			moo->c->synerr.tgt.len = moo->sbuf[MOO_SBUF_ID_SYNERR].len;
+		}
+		else
+		{
+			moo->c->synerr.tgt.ptr = moo->c->synerr_tgtbuf;
+			moo->c->synerr.tgt.len = (tgt->len < MOO_COUNTOF(moo->c->synerr_tgtbuf))? tgt->len: (MOO_COUNTOF(moo->c->synerr_tgtbuf) - 1);
+			moo->c->synerr.tgt.ptr[moo->c->synerr.tgt.len] = '\0';
+			moo_copy_oochars (moo->c->synerr.tgt.ptr, tgt->ptr, moo->c->synerr.tgt.len);
+		}
 	}
 	else 
 	{
@@ -456,7 +468,19 @@ void moo_setsynerrufmt (moo_t* moo, moo_synerrnum_t num, const moo_ioloc_t* loc,
 
 	if (tgt)
 	{
-		moo->c->synerr.tgt = *tgt;
+		if (tgt->len >= MOO_COUNTOF(moo->c->synerr_tgtbuf) && 
+		    moo_copyoocharstosbuf(moo, tgt->ptr, tgt->len, MOO_SBUF_ID_SYNERR) >= 0)
+		{
+			moo->c->synerr.tgt.ptr = moo->sbuf[MOO_SBUF_ID_SYNERR].ptr;
+			moo->c->synerr.tgt.len = moo->sbuf[MOO_SBUF_ID_SYNERR].len;
+		}
+		else
+		{
+			moo->c->synerr.tgt.ptr = moo->c->synerr_tgtbuf;
+			moo->c->synerr.tgt.len = (tgt->len < MOO_COUNTOF(moo->c->synerr_tgtbuf))? tgt->len: (MOO_COUNTOF(moo->c->synerr_tgtbuf) - 1);
+			moo->c->synerr.tgt.ptr[moo->c->synerr.tgt.len] = '\0';
+			moo_copy_oochars (moo->c->synerr.tgt.ptr, tgt->ptr, moo->c->synerr.tgt.len);
+		}
 	}
 	else 
 	{
diff --git a/moo/lib/moo-prv.h b/moo/lib/moo-prv.h
index 865155b..24beab1 100644
--- a/moo/lib/moo-prv.h
+++ b/moo/lib/moo-prv.h
@@ -666,6 +666,7 @@ struct moo_compiler_t
 
 	/* syntax error information */
 	moo_synerr_t synerr;
+	moo_ooch_t synerr_tgtbuf[256];
 
 	/* temporary space used when dealing with an illegal character */
 	moo_ooch_t ilchr;
diff --git a/moo/lib/moo-utl.h b/moo/lib/moo-utl.h
index 997cfbb..edcf956 100644
--- a/moo/lib/moo-utl.h
+++ b/moo/lib/moo-utl.h
@@ -336,15 +336,31 @@ MOO_EXPORT moo_oow_t moo_count_bcstr (
 MOO_EXPORT int moo_copyoocstrtosbuf (
 	moo_t*            moo,
 	const moo_ooch_t* str,
-	int                id
+	int               id
 );
 
 MOO_EXPORT int moo_concatoocstrtosbuf (
 	moo_t*            moo,
 	const moo_ooch_t* str,
-	int                id
+	int               id
 );
 
+
+MOO_EXPORT int moo_copyoocharstosbuf (
+	moo_t*            moo,
+	const moo_ooch_t* ptr,
+	moo_oow_t         len,
+	int               id
+);
+
+MOO_EXPORT int moo_concatoocharstosbuf (
+	moo_t*            moo,
+	const moo_ooch_t* ptr,
+	moo_oow_t         len,
+	int               id
+);
+
+
 #if defined(MOO_OOCH_IS_UCH)
 #	define moo_conv_oocs_to_bcs_with_cmgr(oocs,oocslen,bcs,bcslen,cmgr) moo_conv_ucs_to_bcs_with_cmgr(oocs,oocslen,bcs,bcslen,cmgr)
 #	define moo_conv_oochars_to_bchars_with_cmgr(oocs,oocslen,bcs,bcslen,cmgr) moo_conv_uchars_to_bchars_with_cmgr(oocs,oocslen,bcs,bcslen,cmgr)
diff --git a/moo/lib/moo.c b/moo/lib/moo.c
index 3148683..2ddaeb4 100644
--- a/moo/lib/moo.c
+++ b/moo/lib/moo.c
@@ -837,15 +837,15 @@ int moo_genpfmethod (moo_t* moo, moo_mod_t* mod, moo_oop_class_t _class, moo_met
 
 	/* compose a full primitive function identifier to VM's string buffer.
 	 *   pfid => mod->name + '.' + pfname */
-	if (moo_copyoocstrtosbuf(moo, mod->name, 0) <= -1 ||
-	    moo_concatoocstrtosbuf(moo, dot, 0) <= -1 ||
-	    moo_concatoocstrtosbuf(moo, pfname, 0) <=  -1) 
+	if (moo_copyoocstrtosbuf(moo, mod->name, MOO_SBUF_TMP) <= -1 ||
+	    moo_concatoocstrtosbuf(moo, dot, MOO_SBUF_TMP) <= -1 ||
+	    moo_concatoocstrtosbuf(moo, pfname, MOO_SBUF_TMP) <=  -1) 
 	{
 		MOO_DEBUG2 (moo, "Cannot generate primitive function method [%js] in [%O] - VM memory shortage\n", mthname, _class->name);
 		return -1;
 	}
 
-	pfidsym = (moo_oop_char_t)moo_makesymbol (moo, moo->sbuf[0].ptr, moo->sbuf[0].len);
+	pfidsym = (moo_oop_char_t)moo_makesymbol(moo, moo->sbuf[MOO_SBUF_TMP].ptr, moo->sbuf[MOO_SBUF_TMP].len);
 	if (!pfidsym) 
 	{
 		MOO_DEBUG2 (moo, "Cannot generate primitive function method [%js] in [%O] - symbol instantiation failure\n", mthname, _class->name);
diff --git a/moo/lib/moo.h b/moo/lib/moo.h
index 8032d0b..2404fa6 100644
--- a/moo/lib/moo.h
+++ b/moo/lib/moo.h
@@ -1327,6 +1327,14 @@ typedef struct moo_compiler_t moo_compiler_t;
 
 #define MOO_ERRMSG_CAPA (2048)
 
+enum moo_sbuf_id_t
+{
+	MOO_SBUF_ID_TMP    = 0,
+	MOO_SBUF_ID_SYNERR = 1
+	/* more? */
+};
+
+
 struct moo_t
 {
 	moo_mmgr_t*  mmgr;
diff --git a/moo/lib/utl.c b/moo/lib/utl.c
index 42e2fe1..de07132 100644
--- a/moo/lib/utl.c
+++ b/moo/lib/utl.c
@@ -352,12 +352,15 @@ moo_bch_t* moo_find_bchar_in_bcstr (const moo_bch_t* ptr, moo_bch_t c)
 /* ----------------------------------------------------------------------- */
 
 int moo_concatoocstrtosbuf (moo_t* moo, const moo_ooch_t* str, int id)
+{
+	return moo_concatoocharstosbuf(moo, str, moo_count_oocstr(str), id);
+}
+
+int moo_concatoocharstosbuf (moo_t* moo, const moo_ooch_t* ptr, moo_oow_t len, int id)
 {
 	moo_sbuf_t* p;
-	moo_oow_t len;
 
 	p = &moo->sbuf[id];
-	len = moo_count_oocstr (str);
 
 	if (len > p->capa - p->len)
 	{
@@ -374,7 +377,7 @@ int moo_concatoocstrtosbuf (moo_t* moo, const moo_ooch_t* str, int id)
 		p->capa = newcapa;
 	}
 
-	moo_copy_oochars (&p->ptr[p->len], str, len);
+	moo_copy_oochars (&p->ptr[p->len], ptr, len);
 	p->len += len;
 	p->ptr[p->len] = '\0';
 
@@ -384,7 +387,13 @@ int moo_concatoocstrtosbuf (moo_t* moo, const moo_ooch_t* str, int id)
 int moo_copyoocstrtosbuf (moo_t* moo, const moo_ooch_t* str, int id)
 {
 	moo->sbuf[id].len = 0;;
-	return moo_concatoocstrtosbuf (moo, str, id);
+	return moo_concatoocstrtosbuf(moo, str, id);
+}
+
+int moo_copyoocharstosbuf (moo_t* moo, const moo_ooch_t* ptr, moo_oow_t len, int id)
+{
+	moo->sbuf[id].len = 0;;
+	return moo_concatoocharstosbuf(moo, ptr, len, id);
 }
 
 /* ----------------------------------------------------------------------- */