Index: generic/predefined.h
===================================================================
diff -u -r89fec6ccb2d935530a2ab141440ca343deda3338 -rd3aa8e069917e7ba7d69e936ec4e563b7e0dc34d
--- generic/predefined.h	(.../predefined.h)	(revision 89fec6ccb2d935530a2ab141440ca343deda3338)
+++ generic/predefined.h	(.../predefined.h)	(revision d3aa8e069917e7ba7d69e936ec4e563b7e0dc34d)
@@ -209,10 +209,10 @@
 "-volatile:method,optional,noarg \\\n"
 "arg:initcmd,optional\n"
 "return $parameterdefinitions}\n"
-"::xotcl2::Class create ::xotcl2::ParameterType\n"
-"foreach cmd [info command ::xotcl::cmd::ParameterType::*] {\n"
-"::xotcl::alias ::xotcl2::ParameterType [namespace tail $cmd] $cmd}\n"
-"::xotcl2::ParameterType create ::xotcl2::parameterType\n"
+"::xotcl2::Class create ::xotcl::ParameterSlot\n"
+"foreach cmd [info command ::xotcl::cmd::ParameterSlot::*] {\n"
+"::xotcl::alias ::xotcl::ParameterSlot [namespace tail $cmd] $cmd}\n"
+"::xotcl::ParameterSlot create ::xotcl::parameterSlot\n"
 "proc createBootstrapAttributeSlots {class definitions} {\n"
 "if {![::xotcl::is ${class}::slot object]} {\n"
 "::xotcl2::Object create ${class}::slot}\n"
Index: generic/predefined.xotcl
===================================================================
diff -u -r89fec6ccb2d935530a2ab141440ca343deda3338 -rd3aa8e069917e7ba7d69e936ec4e563b7e0dc34d
--- generic/predefined.xotcl	(.../predefined.xotcl)	(revision 89fec6ccb2d935530a2ab141440ca343deda3338)
+++ generic/predefined.xotcl	(.../predefined.xotcl)	(revision d3aa8e069917e7ba7d69e936ec4e563b7e0dc34d)
@@ -412,14 +412,14 @@
 }
 
 #
-# create class and object for nonpositional argument processing
-::xotcl2::Class create ::xotcl2::ParameterType
-foreach cmd [info command ::xotcl::cmd::ParameterType::*] {
-  ::xotcl::alias ::xotcl2::ParameterType [namespace tail $cmd] $cmd
+# create class and object for parameter slots
+::xotcl2::Class create ::xotcl::ParameterSlot
+foreach cmd [info command ::xotcl::cmd::ParameterSlot::*] {
+  ::xotcl::alias ::xotcl::ParameterSlot [namespace tail $cmd] $cmd
 }
 
 # create an object for dispatching
-::xotcl2::ParameterType create ::xotcl2::parameterType
+::xotcl::ParameterSlot create ::xotcl::parameterSlot
 
 
 # use low level interface for defining slot values. Normally, this is
Index: generic/xotcl.c
===================================================================
diff -u -r89fec6ccb2d935530a2ab141440ca343deda3338 -rd3aa8e069917e7ba7d69e936ec4e563b7e0dc34d
--- generic/xotcl.c	(.../xotcl.c)	(revision 89fec6ccb2d935530a2ab141440ca343deda3338)
+++ generic/xotcl.c	(.../xotcl.c)	(revision d3aa8e069917e7ba7d69e936ec4e563b7e0dc34d)
@@ -6250,7 +6250,7 @@
   Tcl_Obj *ov[5];
   int result, oc;
 
-  ov[0] = XOTclGlobalObjects[XOTE_PARAMETER_TYPE_OBJ];
+  ov[0] = XOTclGlobalObjects[XOTE_PARAMETER_SLOT_OBJ];
   ov[1] = pPtr->converterName;
   ov[2] = pPtr->nameObj;
   ov[3] = objPtr;
@@ -6321,7 +6321,6 @@
 static int
 ParamOptionParse(Tcl_Interp *interp, char *option, int length, int disallowedOptions, XOTclParam *paramPtr) {
   int result = TCL_OK; 
-
   /*fprintf(stderr, "ParamOptionParse name %s, option '%s' (%d) disallowed %.6x\n", paramPtr->name, option, length, disallowedOptions);*/
   if (strncmp(option, "required", MAX(3,length)) == 0) {
     paramPtr->flags |= XOTCL_ARG_REQUIRED;
@@ -6375,7 +6374,7 @@
     XOTclClass *pcl;
     Tcl_Command cmd;
 
-    result = GetObjectFromObj(interp, XOTclGlobalObjects[XOTE_PARAMETER_TYPE_OBJ], &paramObj);
+    result = GetObjectFromObj(interp, XOTclGlobalObjects[XOTE_PARAMETER_SLOT_OBJ], &paramObj);
     if (result != TCL_OK)
       return result;
 
@@ -6386,6 +6385,7 @@
     if (cmd == NULL) {
       fprintf(stderr, "**** could not find checker method %s defined on %s\n",
               ObjStr(checker), objectName(paramObj));
+      paramPtr->flags |= XOTCL_ARG_CURRENTLY_UNKNOWN;
       /* TODO: for the time being, we do not return an error here */
     }
     result = ParamOptionSetConverter(interp, paramPtr, "usertype", convertViaCmd);
@@ -6442,34 +6442,37 @@
     /* we found a ':' */
     int l, start, end;
 
+    /* get parameter name */
     NEW_STRING(paramPtr->name, argString, j);
     paramPtr->nameObj = Tcl_NewStringObj(argName, isNonposArgument ? j-1 : j);
     INCR_REF_COUNT(paramPtr->nameObj);
 
-    /* skip space */
+    /* skip space at begin */
     for (start = j+1; start<length && isspace((int)argString[start]); start++) {;}
 
     /* search for ',' */
     for (l=start; l<length; l++) {
       if (argString[l] == ',') {
+	/* skip space from end */
         for (end = l; end>0 && isspace((int)argString[end-1]); end--);
         result = ParamOptionParse(interp, argString+start, end-start, disallowedOptions, paramPtr);
         if (result != TCL_OK) {
           goto param_error;
         }
         l++;
-        /* skip space */
+        /* skip space from begin */
         for (start = l; start<length && isspace((int)argString[start]); start++) {;}
       }
     }
+    /* skip space from end */
     for (end = l; end>0 && isspace((int)argString[end-1]); end--);
     /* process last option */
     result = ParamOptionParse(interp, argString+start, end-start, disallowedOptions, paramPtr);
     if (result != TCL_OK) {
       goto param_error;
     }
   } else {
-    /* no ':', the whole arg is the name */
+    /* no ':', the whole arg is the name, we have not options */
     NEW_STRING(paramPtr->name, argString, length);
     if (isNonposArgument) {
       paramPtr->nameObj = Tcl_NewStringObj(argName, length-1);
@@ -12147,7 +12150,6 @@
   {-argName "value" -required 0 -type tclobj}
   } */
 static int XOTclValuecheckCmd(Tcl_Interp *interp, Tcl_Obj *objPtr, Tcl_Obj *value) {
-  /* xxxx */
   ClientData checkedData;
   XOTclParam *paramPtr;
   int result;
Index: generic/xotclInt.h
===================================================================
diff -u -red15b5be7e88cbbcdf6121f3869722dbc354d76f -rd3aa8e069917e7ba7d69e936ec4e563b7e0dc34d
--- generic/xotclInt.h	(.../xotclInt.h)	(revision ed15b5be7e88cbbcdf6121f3869722dbc354d76f)
+++ generic/xotclInt.h	(.../xotclInt.h)	(revision d3aa8e069917e7ba7d69e936ec4e563b7e0dc34d)
@@ -358,6 +358,7 @@
 #define XOTCL_ARG_REQUIRED		     0x0001
 #define XOTCL_ARG_MULTIVALUED		     0x0002
 #define XOTCL_ARG_NOARG 		     0x0004
+#define XOTCL_ARG_CURRENTLY_UNKNOWN	     0x0008
 #define XOTCL_ARG_SUBST_DEFAULT		     0x0010
 #define XOTCL_ARG_INITCMD		     0x0020
 #define XOTCL_ARG_METHOD		     0x0040
@@ -367,7 +368,7 @@
 /* disallowed options */
 #define XOTCL_DISALLOWED_ARG_METHOD_PARAMETER	     (XOTCL_ARG_METHOD|XOTCL_ARG_INITCMD|XOTCL_ARG_RELATION)
 #define XOTCL_DISALLOWED_ARG_OBJECT_PARAMETER	     0
-#define XOTCL_DISALLOWED_ARG_VALUEECHECK	     (XOTCL_ARG_SUBST_DEFAULT|XOTCL_ARG_METHOD|XOTCL_ARG_INITCMD|XOTCL_ARG_RELATION|XOTCL_ARG_SWITCH)
+#define XOTCL_DISALLOWED_ARG_VALUEECHECK	     (XOTCL_ARG_SUBST_DEFAULT|XOTCL_ARG_METHOD|XOTCL_ARG_INITCMD|XOTCL_ARG_RELATION|XOTCL_ARG_SWITCH|XOTCL_ARG_CURRENTLY_UNKNOWN)
 
 
 /* method types */
@@ -505,7 +506,7 @@
   XOTE_AUTONAMES, XOTE_DEFAULTMETACLASS, XOTE_DEFAULTSUPERCLASS, 
   XOTE_ALIAS_ARRAY,
   /* object/class names */
-  XOTE_PARAMETER_TYPE_OBJ, 
+  XOTE_PARAMETER_SLOT_OBJ, 
   /* constants */
   XOTE_ALIAS, XOTE_ARGS, XOTE_CMD, XOTE_FILTER, XOTE_FORWARD, 
   XOTE_METHOD, XOTE_OBJECT, XOTE_SETTER, 
@@ -528,7 +529,7 @@
   "__autonames", "__default_metaclass", "__default_superclass", 
   "::xotcl::alias",
   /* object/class names */
-  "::xotcl::parameterType", 
+  "::xotcl::parameterSlot", 
   /* constants */
   "alias", "args", "cmd", "filter",  "forward", 
   "method", "object", "setter", 
Index: tests/parameters.xotcl
===================================================================
diff -u -r89fec6ccb2d935530a2ab141440ca343deda3338 -rd3aa8e069917e7ba7d69e936ec4e563b7e0dc34d
--- tests/parameters.xotcl	(.../parameters.xotcl)	(revision 89fec6ccb2d935530a2ab141440ca343deda3338)
+++ tests/parameters.xotcl	(.../parameters.xotcl)	(revision d3aa8e069917e7ba7d69e936ec4e563b7e0dc34d)
@@ -26,12 +26,14 @@
 ? {::xotcl::valuecheck integer 1} 1
 ? {::xotcl::valuecheck integer,multivalued [list 1 2 3]} 1
 ? {::xotcl::valuecheck integer,multivalued [list 1 2 3 a]} 0
-? {::xotcl::valuecheck in1 aaa} {invalid value constraints "in1"}
 ? {::xotcl::valuecheck object,type=::C c1} 1
 ? {::xotcl::valuecheck object,type=::C o} 0 "object, but different type"
 ? {::xotcl::valuecheck object,type=::C c} 0 "no object"
 ? {::xotcl::valuecheck object,type=::xotcl2::Object c1} 1 "general type"
 
+# do not allow "currently unknown" user defined types in valuecheck
+? {::xotcl::valuecheck in1 aaa} {invalid value constraints "in1"}
+
 #
 # parameter options
 #   required
@@ -62,6 +64,9 @@
 #  objectOfType       YES        YES        NO    NO      YES          YES         YES
 #  userdefined        YES        YES        NO    YES     YES          YES         YES
 
+# MetaSlot create ParameterSlot -parameter {type required multivalued noarg arg}
+
+
 #######################################################
 # objectparameter
 #######################################################
@@ -369,17 +374,8 @@
 #######################################################
 Test case user-types
 
-#
-# create class and object for nonpositional argument processing
-Class create ::xotcl::ParameterType
-foreach cmd [info command ::xotcl::cmd::ParameterType::*] {
-  ::xotcl::alias ::xotcl::ParameterType [namespace tail $cmd] $cmd
-}
-# create an object for dispatching
-::xotcl::ParameterType create ::xotcl::parameterType
-
 # create a userdefined type
-::xotcl::parameterType method type=mytype {name value args} {
+::xotcl::parameterSlot method type=mytype {name value args} {
   if {$value < 1 || $value > 3} {
     error "Value '$value' of parameter $name is not between 1 and 3"
   }
@@ -399,11 +395,11 @@
 }
 
 ? {d1 foo 10} \
-    "::xotcl::parameterType: unable to dispatch method 'type=unknowntype'" \
+    "::xotcl::parameterSlot: unable to dispatch method 'type=unknowntype'" \
     "missing type checker"
 
 # create a userdefined type with a simple argument
-::xotcl::parameterType method type=in {name value arg} {
+::xotcl::parameterSlot method type=in {name value arg} {
   if {$value ni [split $arg |]} {
     error "Value '$value' of parameter $name not in permissible values $arg"
   }
@@ -428,7 +424,7 @@
     "Value 'very good' of parameter b not in permissible values good|bad" \
     "invalid value (not included)"
 
-::xotcl::parameterType method type=range {name value arg} {
+::xotcl::parameterSlot method type=range {name value arg} {
   foreach {min max} [split $arg -] break
   if {$value < $min || $value > $max} {
     error "Value '$value' of parameter $name not between $min and $max"
@@ -453,7 +449,7 @@
 #
 # handling of arg with spaces/arg as list
 #
-::xotcl::parameterType method type=list {name value arg} {
+::xotcl::parameterSlot method type=list {name value arg} {
   #puts $value/$arg
 }
 
@@ -486,17 +482,17 @@
 # are already predefined, define the rest.
 # TODO: should go finally to predefined.
  
-::xotcl::parameterType method type=mixin {name value arg} {
+::xotcl::parameterSlot method type=mixin {name value arg} {
   if {![::xotcl::is $value mixin $arg]} {
     error "Value '$value' of $name has not mixin $arg"
   }
 }
-::xotcl::parameterType method type=baseclass {name value} {
+::xotcl::parameterSlot method type=baseclass {name value} {
   if {![::xotcl::is $value baseclass]} {
     error "Value '$value' of $name is not a baseclass"
   }
 }
-::xotcl::parameterType method type=metaclass {name value} {
+::xotcl::parameterSlot method type=metaclass {name value} {
   if {![::xotcl::is $value metaclass]} {
     error "Value '$value' of $name is not a metaclass"
   }