diff --git a/README.md b/README.md
index cf539327..47b72648 100644
--- a/README.md
+++ b/README.md
@@ -99,11 +99,14 @@ However, the following YANG syntax modules are not implemented (reference to RFC
 - deviation (7.20.3)
 - action (7.15)
 - augment in a uses sub-clause (7.17) (module-level augment is implemented)
+- require-instance
+- instance-identifier type
 - status (7.21.2)
-- extension (7.19)
+- extension (7.19) supported syntactically, but no hooks/plugins for extenstions
 - YIN (13)
 - Yang extended Xpath functions: re-match(), deref)(), derived-from(), derived-from-or-self(), enum-value(), bit-is-set() (10.2-10.6)
 - Default values on leaf-lists are not supported (7.7.2)
+- instance-identifier type
 
 ### Yang patterns
 Yang type patterns use regexps defined in [W3C XML XSD](http://www.w3.org/TR/2004/REC-xmlschema-2-20041028). XSD regexp:s are
diff --git a/apps/cli/cli_common.c b/apps/cli/cli_common.c
index 303942a5..af24ea9c 100644
--- a/apps/cli/cli_common.c
+++ b/apps/cli/cli_common.c
@@ -184,6 +184,40 @@ cli_signal_flush(clicon_handle h)
     cli_signal_block (h);
 }
 
+/*! Transform data 
+ * Add next-last cvv (resolved variable) as body to xml bottom for leaf and 
+ * leaf-list.
+ * There may be some translation necessary.
+ */
+static int
+dbxml_body(cxobj     *xbot,
+	   yang_stmt *ybot,
+	   cvec      *cvv)
+{
+    int     retval = -1;
+    char   *str = NULL;
+    cxobj  *xb;
+    cg_var *cval;
+    int     len;
+
+    len = cvec_len(cvv);
+    cval = cvec_i(cvv, len-1); 
+    if ((str = cv2str_dup(cval)) == NULL){
+	clicon_err(OE_UNIX, errno, "cv2str_dup");
+	goto done;
+    }
+    if ((xb = xml_new("body", xbot, NULL)) == NULL)
+	goto done; 
+    xml_type_set(xb, CX_BODY);
+    if (xml_value_set(xb,  str) < 0)
+	goto done;
+    retval = 0;
+ done:
+    if (str)
+	free(str);
+    return retval;
+}
+
 /*! Modify xml datastore from a callback using xml key format strings
  * @param[in]  h    Clicon handle
  * @param[in]  cvv  Vector of cli string and instantiated variables 
@@ -206,11 +240,11 @@ cli_dbxml(clicon_handle       h,
 	  enum operation_type op)
 {
     int        retval = -1;
-    char      *str = NULL;
+    //    char      *str = NULL;
     char      *api_path_fmt;  /* xml key format */
     char      *api_path = NULL; /* xml key */
-    cg_var    *cval;
-    int        len;
+    //    cg_var    *cval;
+    //    int        len;
     cg_var    *arg;
     cbuf      *cb = NULL;
     yang_stmt *yspec;
@@ -218,7 +252,7 @@ cli_dbxml(clicon_handle       h,
     yang_stmt *y = NULL; /* yang spec of xpath */
     cxobj     *xtop = NULL; /* xpath root */
     cxobj     *xa;           /* attribute */
-    cxobj     *xb;           /* body */
+    //    cxobj     *xb;           /* body */
 
     if (cvec_len(argv) != 1){
 	clicon_err(OE_PLUGIN, 0, "Requires one element to be xml key format string");
@@ -241,22 +275,12 @@ cli_dbxml(clicon_handle       h,
     if ((xa = xml_new("operation", xbot, NULL)) == NULL)
 	goto done;
     xml_type_set(xa, CX_ATTR);
-    if (xml_value_set(xa,  xml_operation2str(op)) < 0)
+    if (xml_value_set(xa, xml_operation2str(op)) < 0)
 	goto done;
     if (yang_keyword_get(y) != Y_LIST && yang_keyword_get(y) != Y_LEAF_LIST){
-	len = cvec_len(cvv);
-	if (len > 1){
-	    cval = cvec_i(cvv, len-1); 
-	    if ((str = cv2str_dup(cval)) == NULL){
-		clicon_err(OE_UNIX, errno, "cv2str_dup");
-		goto done;
-	    }
-	    if ((xb = xml_new("body", xbot, NULL)) == NULL)
-		goto done; 
-	    xml_type_set(xb, CX_BODY);
-	    if (xml_value_set(xb,  str) < 0)
-		goto done;
-	}
+	if (cvec_len(cvv) > 1 &&
+	    dbxml_body(xbot, y, cvv) < 0)
+	    goto done;
     }
     if ((cb = cbuf_new()) == NULL){
 	clicon_err(OE_XML, errno, "cbuf_new");
@@ -274,8 +298,6 @@ cli_dbxml(clicon_handle       h,
  done:
     if (cb)
 	cbuf_free(cb);
-    if (str)
-	free(str);
     if (api_path)
 	free(api_path);  
     if (xtop)
diff --git a/apps/cli/cli_generate.c b/apps/cli/cli_generate.c
index 5a0c4cf6..1d9400d3 100644
--- a/apps/cli/cli_generate.c
+++ b/apps/cli/cli_generate.c
@@ -530,7 +530,7 @@ yang2cli_var(clicon_handle h,
 	     cbuf         *cb)
 {
     int           retval = -1;
-    char         *origtype;
+    char         *origtype = NULL;
     yang_stmt    *yrestype; /* resolved type */
     char         *restype; /* resolved type */
     cvec         *cvv = NULL; 
@@ -596,6 +596,8 @@ yang2cli_var(clicon_handle h,
     }
     retval = 0;
   done:
+    if (origtype)
+	free(origtype);
     if (patterns)
 	cvec_free(patterns);
     return retval;
diff --git a/include/clixon_custom.h b/include/clixon_custom.h
index 1127dfce..b36a54ab 100644
--- a/include/clixon_custom.h
+++ b/include/clixon_custom.h
@@ -48,3 +48,9 @@
  */
 #define USE_NETCONF_NS_AS_DEFAULT
 
+/* Use modulename:id instead of prefix:id in derived identityref list
+ * Modulenames are global/canonical but prefixes are not.
+ * Experimental since there is some mapping between prefixes and module names
+ * that needs to be done
+ */
+#undef USE_IDREF_LIST_MODULE
diff --git a/lib/clixon/clixon_xml_map.h b/lib/clixon/clixon_xml_map.h
index 0b3b9842..6730b02d 100644
--- a/lib/clixon/clixon_xml_map.h
+++ b/lib/clixon/clixon_xml_map.h
@@ -44,6 +44,7 @@ typedef enum yang_class yang_class;
 /*
  * Prototypes
  */
+int isxmlns(cxobj *x);
 int xml2txt(FILE *f, cxobj *x, int level);
 int xml2cli(FILE *f, cxobj *x, char *prepend, enum genmodel_type gt);
 int xml_yang_root(cxobj *x, cxobj **xr);
diff --git a/lib/clixon/clixon_yang.h b/lib/clixon/clixon_yang.h
index 1c8c3e7b..c703f4f0 100644
--- a/lib/clixon/clixon_yang.h
+++ b/lib/clixon/clixon_yang.h
@@ -164,8 +164,6 @@ yang_stmt *ys_dup(yang_stmt *old);
 int        yn_insert(yang_stmt *ys_parent, yang_stmt *ys_child);
 yang_stmt *yn_each(yang_stmt *yn, yang_stmt *ys);
 char      *yang_key2str(int keyword);
-char      *yarg_prefix(yang_stmt *ys);
-char      *yarg_id(yang_stmt *ys);
 int        ys_module_by_xml(yang_stmt *ysp, struct xml *xt, yang_stmt **ymodp);
 yang_stmt *ys_module(yang_stmt *ys);
 yang_stmt *ys_real_module(yang_stmt *ys);
diff --git a/lib/src/clixon_datastore_write.c b/lib/src/clixon_datastore_write.c
index 594a9305..9689ed4e 100644
--- a/lib/src/clixon_datastore_write.c
+++ b/lib/src/clixon_datastore_write.c
@@ -83,6 +83,45 @@
 #include "clixon_datastore_read.h"
 #include "clixon_datastore_tree.h"
 
+/*! Replace all xmlns attributes in x0 with xmlns attributes in x1
+ * This is an embryo of code to actually check if namespace binding is canonical
+ * and if it is not, either return error or transform to canonical.
+ * "Canonical" meaning comply to the yang module prefixes.
+ * The current code does not really do anything useful
+ */
+static int
+replace_xmlns(cxobj *x0,
+	      cxobj *x1)
+{
+    int    retval = -1;
+    cxobj *x = NULL;
+    cxobj *xcopy;
+    int    i;
+
+    for (i=0; i<xml_child_nr(x0); ){
+	x = xml_child_i(x0, i);
+	if (!isxmlns(x)){
+	    i++;
+	    continue;
+	}
+	xml_rm(x);
+	xml_free(x);
+    }
+    x = NULL;
+    while ((x = xml_child_each(x1, x, CX_ATTR)) != NULL) {
+	/* split and only add xmlns= and xmlns:x= attributes! */
+	if (!isxmlns(x))
+	    continue;
+	if ((xcopy = xml_new(xml_name(x), x0, xml_spec(x))) == NULL)
+	    goto done;
+	if (xml_copy(x, xcopy) < 0) /* recursion */
+	    goto done;
+    }
+    retval = 0;
+ done:
+    return retval;
+}
+
 /*! Modify a base tree x0 with x1 with yang spec y according to operation op
  * @param[in]  th       Datastore text handle
  * @param[in]  x0       Base xml tree (can be NULL in add scenarios)
@@ -187,6 +226,16 @@ text_modify(clicon_handle       h,
 		    xml_type_set(x0b, CX_BODY);
 		}
 	    }
+	    else {  /* if change existing node, replace xmlns attributes 
+		     * This is only done for leaf/leaf-list now, eg terminals
+		     * and is only an embryo of checking canonical namespace
+		     * bindings.
+		     * But it does catch some cornercases where a new
+		     * namespace binding is replacing an old for eg identityref
+		     */
+		if (replace_xmlns(x0, x1) < 0)
+		    goto done;
+	    }
 	    if (x1bstr){
 		if ((x0b = xml_body_get(x0)) != NULL){
 		    x0bstr = xml_value(x0b);
diff --git a/lib/src/clixon_string.c b/lib/src/clixon_string.c
index bab388b2..014ce52b 100644
--- a/lib/src/clixon_string.c
+++ b/lib/src/clixon_string.c
@@ -623,8 +623,8 @@ clicon_str2int_search(const map_str2int *mstab,
 
 /*! Split colon-separated node identifier into prefix and name
  * @param[in]  node-id
- * @param[out] prefix  Malloced string. May be NULL.
- * @param[out] id      Malloced identifier.
+ * @param[out] prefix  If non-NULL, return malloced string, or NULL.
+ * @param[out] id      If non-NULL, return malloced identifier.
  * @retval     0       OK
  * @retval    -1       Error
  * @code
@@ -647,19 +647,21 @@ nodeid_split(char  *nodeid,
     char *str;
     
     if ((str = strchr(nodeid, ':')) == NULL){
-	if ((*id = strdup(nodeid)) == NULL){
+	if (id && (*id = strdup(nodeid)) == NULL){
 	    clicon_err(OE_YANG, errno, "strdup");
 	    goto done;
 	}
     }
-    else{
-	if ((*prefix = strdup(nodeid)) == NULL){
-	    clicon_err(OE_YANG, errno, "strdup");
-	    goto done;
+    else {
+	if (prefix){
+	    if ((*prefix = strdup(nodeid)) == NULL){
+		clicon_err(OE_YANG, errno, "strdup");
+		goto done;
+	    }
+	    (*prefix)[str-nodeid] = '\0';
 	}
-	(*prefix)[str-nodeid] = '\0';
 	str++;
-	if ((*id = strdup(str)) == NULL){
+	if (id && (*id = strdup(str)) == NULL){
 	    clicon_err(OE_YANG, errno, "strdup");
 	    goto done;
 	}
diff --git a/lib/src/clixon_xml_map.c b/lib/src/clixon_xml_map.c
index 7f9c3a3a..04d8c020 100644
--- a/lib/src/clixon_xml_map.c
+++ b/lib/src/clixon_xml_map.c
@@ -94,6 +94,22 @@
 #include "clixon_yang_type.h"
 #include "clixon_xml_map.h"
 
+/*! Is attribute and is either of form xmlns="", or xmlns:x="" */
+int
+isxmlns(cxobj *x)
+{
+    char *prefix = NULL;
+
+    if (xml_type(x) != CX_ATTR)
+	return 0;
+    if (strcmp(xml_name(x), "xmlns")==0)
+	return 1;
+    if ((prefix = xml_prefix(x)) != NULL
+	&& strcmp(xml_prefix(x), "xmlns")==0)
+	return 1;
+    return 0;
+}
+
 /*! x is element and has eactly one child which in turn has none */
 static int
 tleaf(cxobj *x)
@@ -344,27 +360,28 @@ validate_identityref(cxobj     *xt,
 {
     int         retval = -1;
     char       *node = NULL;
+    char       *idref = NULL;
     yang_stmt  *ybaseref; /* This is the type's base reference */
     yang_stmt  *ybaseid;
     char       *prefix = NULL;
+    char       *id = NULL;
+    cbuf       *cberr = NULL;
     cbuf       *cb = NULL;
-    cbuf       *cb2 = NULL;
-
-    /* Get idref value. Then see if this value is derived from ytype.
-     * Always add default prefix because derived identifiers are stored with
-     * prefixes in the base identifiers derived-list.
-     */
+    
     if ((cb = cbuf_new()) == NULL){
 	clicon_err(OE_UNIX, errno, "cbuf_new"); 
 	goto done;
     }
+    if ((cberr = cbuf_new()) == NULL){
+	clicon_err(OE_UNIX, errno, "cbuf_new"); 
+	goto done;
+    }
+    /* Get idref value. Then see if this value is derived from ytype.
+     */
     if ((node = xml_body(xt)) == NULL)
 	return 0;
-    if (strchr(node, ':') == NULL){
-	prefix = yang_find_myprefix(ys);
-	cprintf(cb, "%s:%s", prefix, node);
-	node = cbuf_get(cb);
-    }
+    if (nodeid_split(node, &prefix, &id) < 0)
+	goto done;
     /* This is the type's base reference */
     if ((ybaseref = yang_find(ytype, Y_BASE, NULL)) == NULL){
 	if (netconf_missing_element_xml(xret, "application", yang_argument_get(ytype), "Identityref validation failed, no base") < 0)
@@ -377,26 +394,73 @@ validate_identityref(cxobj     *xt,
 	    goto done;
 	goto fail;
     }
+
+#if 0 /* Assume proper namespace, otherwise we assume module prefixes */
+    {
+	char       *namespace;
+	yang_stmt  *ymod;
+	yang_stmt  *yspec;    
+
+	/* Create an idref as <module>:<id> which is the format of the derived
+	 * identityref list associated with the base identities.
+	 */
+	/* Get namespace (of idref) from xml */
+	if (xml2ns(xt, prefix, &namespace) < 0)
+	    goto done;
+	yspec = ys_spec(ys);
+	/* Get module of that namespace */
+	if ((ymod = yang_find_module_by_namespace(yspec,  namespace)) == NULL){
+	    clicon_err(OE_YANG, ENOENT, "No module found"); 
+	    goto done;
+	}
+	cprintf(cb, "%s:%s", yang_argument_get(ymod), id);
+    }
+#else
+#ifdef USE_IDREF_LIST_MODULE
+    {
+	yang_stmt  *ymod;
+	/* idref from prefix:id to module:id */
+	if (prefix == NULL)
+	    ymod = ys_module(ys);
+	else /* from prefix to name */
+	    ymod = yang_find_module_by_prefix(ys, prefix);
+	if (ymod == NULL){
+	    cprintf(cberr, "Identityref validation failed, %s not derived from %s", 
+		    node, yang_argument_get(ybaseid));
+	    if (netconf_operation_failed_xml(xret, "application", cbuf_get(cberr)) < 0)
+		goto done;
+	    goto fail;
+	}
+	cprintf(cb, "%s:%s", yang_argument_get(ymod), id);
+    }
+#else
+    if (prefix == NULL)
+       cprintf(cb, "%s:%s", yang_find_myprefix(ys), id);
+    else
+       cprintf(cb, "%s:%s", prefix, id);
+#endif
+#endif
+    idref = cbuf_get(cb);	
     /* Here check if node is in the derived node list of the base identity 
      * The derived node list is a cvec computed XXX
      */
-    if (cvec_find(yang_cvec_get(ybaseid), node) == NULL){
-	if ((cb2 = cbuf_new()) == NULL){
-	    clicon_err(OE_UNIX, errno, "cbuf_new"); 
-	    goto done;
-	}
-	cprintf(cb2, "Identityref validation failed, %s not derived from %s", 
+    if (cvec_find(yang_cvec_get(ybaseid), idref) == NULL){
+	cprintf(cberr, "Identityref validation failed, %s not derived from %s", 
 		node, yang_argument_get(ybaseid));
-	if (netconf_operation_failed_xml(xret, "application", cbuf_get(cb2)) < 0)
+	if (netconf_operation_failed_xml(xret, "application", cbuf_get(cberr)) < 0)
 	    goto done;
 	goto fail;
     }
     retval = 1;
  done:
+    if (cberr)
+	cbuf_free(cberr);
     if (cb)
 	cbuf_free(cb);
-    if (cb2)
-	cbuf_free(cb2);
+    if (id)
+	free(id);
+    if (prefix)
+	free(prefix);
     return retval;
  fail:
     retval = 0;
diff --git a/lib/src/clixon_yang.c b/lib/src/clixon_yang.c
index 3e2cff9e..656c889e 100644
--- a/lib/src/clixon_yang.c
+++ b/lib/src/clixon_yang.c
@@ -1102,44 +1102,6 @@ ys_spec(yang_stmt *ys)
     return (yang_stmt*)ys;
 }
 
-/* Assume argument is id on the type: <[prefix:]id>, return 'id'
- * Just return string from id
- * @param[in] ys      A yang statement
- * @retval    NULL    No id (argument is NULL)
- * @retval    id      Pointer to identifier
- * @see yarg_prefix
- */
-char*
-yarg_id(yang_stmt *ys)
-{
-    char   *id;
-    
-    if ((id = strchr(ys->ys_argument, ':')) == NULL)
-	id = ys->ys_argument;
-    else
-	id++;
-    return id;
-}
-
-/*! Assume argument is id on the type: <[prefix:]id>, return 'prefix'
- * @param[in] ys      A yang statement
- * @retval    NULL    No prefix
- * @retval    prefix  Malloced string that needs to be freed by caller.
- * @see yarg_id
- */
-char*
-yarg_prefix(yang_stmt *ys)
-{
-    char   *id;
-    char   *prefix = NULL;
-    
-    if ((id = strchr(ys->ys_argument, ':')) != NULL){
-	prefix = strdup(ys->ys_argument);
-	prefix[id-ys->ys_argument] = '\0';
-    }
-    return prefix;
-}
-
 /*! Given a yang statement and a prefix, return yang module to that relative prefix
  * Note, not the other module but the proxy import statement only
  * @param[in]  ys      A yang statement
@@ -1333,8 +1295,8 @@ yang_print_cbuf(cbuf      *cb,
  * 4. Check if leaf is part of list, if key exists mark leaf as key/unique 
  * XXX: extend type search
  *
+ * @param[in] h    Clicon handle
  * @param[in] ys   The yang statement to populate.
- * @param[in] arg  A void argument not used
  * @retval    0    OK
  * @retval    -1   Error with clicon_err called
  */
@@ -1352,17 +1314,17 @@ ys_populate_leaf(clicon_handle h,
     char           *reason = NULL;
     yang_stmt      *yrestype;  /* resolved type */
     char           *restype;  /* resolved type */
-    char           *type;   /* original type */
+    char           *origtype=NULL;   /* original type */
     uint8_t         fraction_digits;
     int             options = 0x0;
 
     yparent = ys->ys_parent;     /* Find parent: list/container */
     /* 1. Find type specification and set cv type accordingly */
-    if (yang_type_get(ys, &type, &yrestype, &options, NULL, NULL, NULL, &fraction_digits)
+    if (yang_type_get(ys, &origtype, &yrestype, &options, NULL, NULL, NULL, &fraction_digits)
  < 0)
 	goto done;
     restype = yrestype?yrestype->ys_argument:NULL;
-    if (clicon_type2cv(type, restype, ys, &cvtype) < 0) /* This handles non-resolved also */
+    if (clicon_type2cv(origtype, restype, ys, &cvtype) < 0) /* This handles non-resolved also */
 	goto done;
     /* 2. Create the CV using cvtype and name it */
     if ((cv = cv_new(cvtype)) == NULL){
@@ -1402,11 +1364,17 @@ ys_populate_leaf(clicon_handle h,
     ys->ys_cv = cv;
     retval = 0;
   done:
+    if (origtype)
+	free(origtype);
     if (cv && retval < 0)
 	cv_free(cv);
     return retval;
 }
 
+/*! Populate list yang statement
+ * @param[in] h    Clicon handle
+ * @param[in] ys   The yang statement (type) to populate.
+ */
 static int
 ys_populate_list(clicon_handle h,
 		 yang_stmt    *ys)
@@ -1505,6 +1473,8 @@ range_parse(yang_stmt   *ys,
 /*! Populate string built-in range statement
  *
  * Create cvec variables "range_min" and "range_max". Assume parent is type.
+ * @param[in] h    Clicon handle
+ * @param[in] ys   The yang statement (range) to populate.
  * Actually: bound[..bound] (| bound[..bound])*  
  *   where bound is integer, decimal or keywords 'min' or 'max. 
  * RFC 7950 9.2.4:
@@ -1519,10 +1489,10 @@ ys_populate_range(clicon_handle h,
 		  yang_stmt    *ys)
 {
     int             retval = -1;
-    yang_stmt      *yparent;        /* type */
-    char           *origtype;  /* orig type */
-    yang_stmt      *yrestype;   /* resolved type */
-    char           *restype;   /* resolved type */
+    yang_stmt      *yparent;         /* type */
+    char           *origtype = NULL; /* orig type */
+    yang_stmt      *yrestype;        /* resolved type */
+    char           *restype;         /* resolved type */
     int             options = 0x0;
     uint8_t         fraction_digits;
     enum cv_type    cvtype = CGV_ERR;
@@ -1536,7 +1506,8 @@ ys_populate_range(clicon_handle h,
 			  &options, NULL, NULL, NULL, &fraction_digits) < 0)
 	goto done;
     restype = yrestype?yrestype->ys_argument:NULL;
-    origtype = yarg_id((yang_stmt*)yparent);
+    if (nodeid_split(yang_argument_get(yparent), NULL, &origtype) < 0)
+	 goto done;
     /* This handles non-resolved also */
     if (clicon_type2cv(origtype, restype, ys, &cvtype) < 0) 
 	goto done;
@@ -1548,15 +1519,21 @@ ys_populate_range(clicon_handle h,
 	goto done;
     retval = 0;
   done:
+    if (origtype)
+	free(origtype);
     return retval;
 }
 
 /*! Populate integer built-in length statement
  *
  * Create cvec variables "range_min" and "range_max". Assume parent is type.
+ * @param[in] h    Clicon handle
+ * @param[in] ys   The yang statement (length) to populate.
+ *
  * Actually: len[..len] (| len[..len])*  
- *   len is unsigned integer or keywords 'min' or 'max. 
- * RFC 7950 9.4.4
+ *   len is unsigned integer or keywords 'min' or 'max'
+ *
+ * From RFC 7950 Sec 9.4.4:
  *  A length range consists of an explicit value, or a lower bound, two
  *  consecutive dots "..", and an upper bound.  Multiple values or ranges
  *  can be given, separated by "|".  Length-restricting values MUST NOT
@@ -1586,8 +1563,8 @@ ys_populate_length(clicon_handle h,
 
 /*! Sanity check yang type statement
  * XXX: Replace with generic parent/child type-check
+ * @param[in] h    Clicon handle
  * @param[in] ys   The yang statement (type) to populate.
- * @
  */
 static int
 ys_populate_type(clicon_handle h,
@@ -1620,12 +1597,15 @@ ys_populate_type(clicon_handle h,
     return retval;
 }
 
-/*! Sanity check yang identity statement recursively
+/*! Sanity check yang identity statement recursively and create derived id list
  *
- * Find base identities if any and add this identity to derived list.
+ * Find base identities if any and add this identity to derived identity list.
  * Do this recursively
- * @param[in] ys   The yang identity to populate.
- * @param[in] arg  If set contains a derived identifier
+ * The derived identity list is a list of <module>:<id> pairs. Prefixes cannot
+ * be used since they are local in scope.
+ * @param[in] h     Clicon handle
+ * @param[in] ys    The yang identity to populate.
+ * @param[in] idref If set contains the derived identifier(NULL on top call)
  * @see validate_identityref  which in runtime validates actual values
  */
 static int
@@ -1636,28 +1616,40 @@ ys_populate_identity(clicon_handle h,
     int             retval = -1;
     yang_stmt      *yc = NULL;
     yang_stmt      *ybaseid;
+    //    yang_stmt      *ymod;
     cg_var         *cv;
-    char           *derid;
     char           *baseid;
     char           *prefix = NULL;
+    char           *id = NULL;
     cbuf           *cb = NULL;
-    char           *p;
 
+    /* Top-call (no recursion) create idref 
+     * The idref is (here) in "canonical form": <module>:<id>
+     */
     if (idref == NULL){
 	/* Create derived identity through prefix:id if not recursively called*/
-	derid = ys->ys_argument; /* derived id */
-	if ((prefix = yarg_prefix(ys)) == NULL){
-	    if ((p = yang_find_myprefix(ys)) != NULL)
-		prefix = strdup(yang_find_myprefix(ys));
-	}
 	if ((cb = cbuf_new()) == NULL){
 	    clicon_err(OE_UNIX, errno, "cbuf_new"); 
 	    goto done;
 	}
-	if (prefix)
-	    cprintf(cb, "%s:%s", prefix, derid);
-	else
-	    cprintf(cb, "%s", derid);
+#if 0 /* Use module:id instead of prefix:id in derived list */
+	if (nodeid_split(yang_argument_get(ys), &prefix, &id) < 0)
+	    goto done;
+	if ((ymod = ys_module(ys)) == NULL){
+	    clicon_err(OE_YANG, ENOENT, "No module found"); 
+	    goto done;
+	}
+	cprintf(cb, "%s:%s", yang_argument_get(ymod), id);
+#else
+	{
+	    if (nodeid_split(yang_argument_get(ys), &prefix, &id) < 0)
+		goto done;
+	    if (prefix)
+		cprintf(cb, "%s:%s", prefix, id);
+	    else
+		cprintf(cb, "%s:%s", yang_find_myprefix(ys), id);
+	}
+#endif
 	idref = cbuf_get(cb);
     }
     /* Iterate through all base statements and check the base identity exists 
@@ -1667,9 +1659,9 @@ ys_populate_identity(clicon_handle h,
     while ((yc = yn_each(ys, yc)) != NULL) {
 	if (yc->ys_keyword != Y_BASE)
 	    continue;
-	baseid = yc->ys_argument;
+	baseid = yang_argument_get(yc); /* on the form: prefix:id */
 	if (((ybaseid = yang_find_identity(ys, baseid))) == NULL){
-	    clicon_err(OE_YANG, 0, "No such identity: %s", baseid); 
+	    clicon_err(OE_YANG, ENOENT, "No such identity: %s", baseid); 
 	    goto done;
 	}
 	//	    continue; /* root identity */
@@ -1696,6 +1688,8 @@ ys_populate_identity(clicon_handle h,
   done:
     if (prefix)
 	free(prefix);
+    if (id)
+	free(id);
     if (cb)
 	cbuf_free(cb);
     return retval;
@@ -1730,8 +1724,8 @@ if_feature(yang_stmt    *yspec,
 
 /*! Populate yang feature statement - set cv to 1 if enabled
  *
- * @param[in] ys   Feature yang statement to populate.
  * @param[in] h    Clicon handle
+ * @param[in] ys   Feature yang statement to populate.
  */
 static int
 ys_populate_feature(clicon_handle h,
@@ -1792,6 +1786,8 @@ ys_populate_feature(clicon_handle h,
 }
 
 /*! Populate the unique statement with a cvec
+ * @param[in] h    Clicon handle
+ * @param[in] ys   The yang statement (unique) to populate.
  */
 static int
 ys_populate_unique(clicon_handle h,
@@ -1805,6 +1801,8 @@ ys_populate_unique(clicon_handle h,
 }
 
 /*! Populate unknown node with extension
+ * @param[in] h    Clicon handle
+ * @param[in] ys   The yang statement (unknown) to populate.
  */
 static int
 ys_populate_unknown(clicon_handle h,
@@ -1815,19 +1813,19 @@ ys_populate_unknown(clicon_handle h,
     char      *reason = NULL;
     yang_stmt *ymod;
     char      *prefix = NULL;
-    char      *name;
+    char      *id = NULL;
     char      *extra;
 
     if ((extra = ys->ys_extra) == NULL)
 	goto ok;
     /* Find extension, if found, store it as unknown, if not,
        break for error */
-    prefix  = yarg_prefix(ys); /* And this its prefix */
-    name    = yarg_id(ys);     /* This is the type to resolve */
+    if (nodeid_split(yang_argument_get(ys), &prefix, &id) < 0)
+	goto done;
     if ((ymod = yang_find_module_by_prefix(ys, prefix)) == NULL)
 	goto ok; /* shouldnt happen */
-    if (yang_find(ymod, Y_EXTENSION, name) == NULL){
-	clicon_err(OE_YANG, errno, "Extension %s:%s not found", prefix, name);
+    if (yang_find(ymod, Y_EXTENSION, id) == NULL){
+	clicon_err(OE_YANG, errno, "Extension %s:%s not found", prefix, id);
 	goto done;
     }
     if ((ys->ys_cv = cv_new(CGV_STRING)) == NULL){
@@ -1847,13 +1845,15 @@ ys_populate_unknown(clicon_handle h,
  done:
     if (prefix)
 	free(prefix);
+    if (id)
+	free(id);
     return retval;
 }
 
 /*! Populate with cligen-variables, default values, etc. Sanity checks on complete tree.
  *
  * @param[in]  ys  Yang statement
- * @param[in]  h   Clicon handle
+ * @param[in]  arg Argument - in effect Clicon handle
  * Preferably run this command using yang_apply
  * Done in 2nd pass after complete parsing to be sure to have a complete
  * parse-tree
@@ -2150,8 +2150,8 @@ yang_expand_grouping(yang_stmt *yn)
     int        glen;
     int        i;
     int        j;
-    char      *name;
-    char      *prefix;
+    char      *id = NULL;
+    char      *prefix = NULL;
     size_t     size;
 
     /* Cannot use yang_apply here since child-list is modified (is destructive) */
@@ -2161,14 +2161,18 @@ yang_expand_grouping(yang_stmt *yn)
 	switch(ys->ys_keyword){
 	case Y_USES:
 	    /* Split argument into prefix and name */
-	    name = yarg_id(ys);     /* This is uses/grouping name to resolve */
-	    prefix  = yarg_prefix(ys); /* And this its prefix */
-	    if (ys_grouping_resolve(ys, prefix, name, &ygrouping) < 0)
+	    if (nodeid_split(yang_argument_get(ys), &prefix, &id) < 0)
+		goto done;
+	    if (ys_grouping_resolve(ys, prefix, id, &ygrouping) < 0)
 		goto done;
 	    if (prefix){
 		free(prefix); 
 		prefix = NULL;
 	    }
+	    if (id){
+		free(id); 
+		id = NULL;
+	    }
 	    if (ygrouping == NULL){
 		clicon_log(LOG_NOTICE, "%s: Yang error : grouping \"%s\" not found in module \"%s\"", 
 			   __FUNCTION__, ys->ys_argument, ys_module(ys)->ys_argument);
@@ -2258,6 +2262,10 @@ yang_expand_grouping(yang_stmt *yn)
     }
     retval = 0;
  done:
+    if (prefix)
+	free(prefix); 
+    if (id)
+	free(id); 
     return retval;
 }
 
diff --git a/lib/src/clixon_yang_internal.h b/lib/src/clixon_yang_internal.h
index 12edd24c..665fb512 100644
--- a/lib/src/clixon_yang_internal.h
+++ b/lib/src/clixon_yang_internal.h
@@ -96,7 +96,8 @@ struct yang_stmt{
     cvec              *ys_cvec;      /* List of stmt-specific variables 
 					Y_RANGE: range_min, range_max 
 					Y_LIST: vector of keys
-					Y_TYPE & identity: store all derived types
+					Y_TYPE & identity: store all derived 
+					   types as <prefix>:<id> list
 				     */
     yang_type_cache   *ys_typecache; /* If ys_keyword==Y_TYPE, cache all typedef data except unions */
     int               _ys_vector_i;   /* internal use: yn_each */
diff --git a/lib/src/clixon_yang_type.c b/lib/src/clixon_yang_type.c
index 36818ecd..b665dca3 100644
--- a/lib/src/clixon_yang_type.c
+++ b/lib/src/clixon_yang_type.c
@@ -1058,7 +1058,7 @@ ys_cv_validate(clicon_handle h,
     cvec           *patterns = NULL;
     cvec           *regexps = NULL;
     enum cv_type    cvtype;
-    char           *type;  /* orig type */
+    char           *origtype = NULL;  /* orig type */
     yang_stmt      *yrestype; /* resolved type */
     char           *restype;
     uint8_t         fraction = 0; 
@@ -1081,13 +1081,13 @@ ys_cv_validate(clicon_handle h,
 	clicon_err(OE_UNIX, errno, "cvec_new");
 	goto done;
     }
-    if (yang_type_get(ys, &type, &yrestype, 
+    if (yang_type_get(ys, &origtype, &yrestype, 
 		      &options, &cvv,
 		      patterns, regexps,
 		      &fraction) < 0)
 	goto done;
     restype = yrestype?yrestype->ys_argument:NULL;
-    if (clicon_type2cv(type, restype, ys, &cvtype) < 0)
+    if (clicon_type2cv(origtype, restype, ys, &cvtype) < 0)
 	goto done;
 
     if (cv_type_get(ycv) != cvtype){
@@ -1104,7 +1104,7 @@ ys_cv_validate(clicon_handle h,
     if (restype && strcmp(restype, "union") == 0){ 
 	assert(cvtype == CGV_REST);
 	val = cv_string_get(cv);
-	if ((retval2 = ys_cv_validate_union(h, ys, reason, yrestype, type, val)) < 0)
+	if ((retval2 = ys_cv_validate_union(h, ys, reason, yrestype, origtype, val)) < 0)
 	    goto done;
 	retval = retval2; /* invalid (0) with latest reason or valid 1 */
     }
@@ -1127,6 +1127,8 @@ ys_cv_validate(clicon_handle h,
 	    goto done;
     }
   done:
+    if (origtype)
+	free(origtype);
     if (regexps)
 	cvec_free(regexps);
     if (patterns)
@@ -1165,48 +1167,43 @@ ys_typedef_up(yang_stmt *ys)
 }
 
 /*! Find identity yang-stmt
-  This is a sanity check of base identity of identity-ref and for identity 
-  statements when parsing.
-
-  Return true if node is identityref and is derived from identity_name
-  The derived-from() function returns true if the (first) node (in
-   document order in the argument "nodes") is a node of type identityref,
-   and its value is an identity that is derived from the identity
-   "identity-name" defined in the YANG module "module-name"; otherwise
-   it returns false.
-
- Valid values for an identityref are any identities derived from the
-   identityref's base identity. 
-   1. (base) identity must exist (be found). This is a sanity check
-     of the specification and also necessary for identity statements.
-   (This is what is done here)
-   2. Check if a given node has value derived from base identity. This is
-      a run-time check necessary when validating eg netconf.
-   (This is validation)
-   3. Find all valid derived identities from a identityref base identity.
-   (This is for cli generation)
-   * @param[in] ys        Yang spec of id statement
-   * @param[in] identity  Identity string -check if it exists
-   * @retval    0        OK
- *  @see validate_identityref for (2) above
+ *  This is a sanity check of base identity of identity-ref and for identity 
+ *  statements when parsing.
+ *
+ * Return true if node is identityref and is derived from identity_name
+ * The derived-from() function returns true if the (first) node (in
+ * document order in the argument "nodes") is a node of type identityref,
+ * and its value is an identity that is derived from the identity
+ * "identity-name" defined in the YANG module "module-name"; otherwise
+ *  it returns false.
+ *
+ * Valid values for an identityref are any identities derived from the
+ *  identityref's base identity. 
+ *   1. (base) identity must exist (be found). This is a sanity check
+ *   of the specification and also necessary for identity statements.
+ *  (This is what is done here)
+ *  2. Check if a given node has value derived from base identity. This is
+ *     a run-time check necessary when validating eg netconf.
+ *  (This is validation)
+ *  3. Find all valid derived identities from a identityref base identity.
+ *  (This is for cli generation)
+ * @param[in] ys        Yang spec of id statement
+ * @param[in] identity  Identity string -check if it exists
+ * @retval    0        OK
+ * @see validate_identityref for (2) above
  */
 yang_stmt *
 yang_find_identity(yang_stmt *ys, 
 		   char      *identity)
 {
-    char        *id;
+    char        *id = NULL;
     char        *prefix = NULL;
     yang_stmt   *ymodule;
     yang_stmt   *yid = NULL;
     yang_stmt   *yn;
 
-    if ((id = strchr(identity, ':')) == NULL)
-	id = identity;
-    else{
-	prefix = strdup(identity);
-	prefix[id-identity] = '\0';
-	id++;
-    }
+    if (nodeid_split(identity, &prefix, &id) < 0)
+	goto done;
     /* No, now check if identityref is derived from base */
     if (prefix){ /* Go to top and find import that matches */
 	if ((ymodule = yang_find_module_by_prefix(ys, prefix)) == NULL)
@@ -1231,6 +1228,8 @@ yang_find_identity(yang_stmt *ys,
 	}
     }
   done:
+    if (id)
+	free(id);
     if (prefix)
 	free(prefix);
     return yid;
@@ -1334,7 +1333,7 @@ yang_type_resolve(yang_stmt   *yorig,
 {
     yang_stmt   *rytypedef = NULL; /* Resolved typedef of ytype */
     yang_stmt   *rytype;           /* Resolved type of ytype */
-    char        *type;
+    char        *type = NULL;
     char        *prefix = NULL;
     int          retval = -1;
     yang_stmt   *yn;
@@ -1343,8 +1342,9 @@ yang_type_resolve(yang_stmt   *yorig,
     if (options)
 	*options = 0x0;
     *yrestype    = NULL; /* Initialization of resolved type that may not be necessary */
-    type      = yarg_id(ytype);     /* This is the type to resolve */
-    prefix    = yarg_prefix(ytype); /* And this its prefix */
+
+    if (nodeid_split(yang_argument_get(ytype), &prefix, &type) < 0)
+	goto done;
     /* Cache does not work for eg string length 32? */
     if (ytype->ys_typecache != NULL){
 	if (yang_type_cache_get(ytype->ys_typecache, yrestype,
@@ -1409,6 +1409,8 @@ yang_type_resolve(yang_stmt   *yorig,
   done:
     if (prefix)
 	free(prefix);
+    if (type)
+	free(type);
     return retval;
 }
 
@@ -1432,7 +1434,7 @@ yang_type_resolve(yang_stmt   *yorig,
  *      printf("%d..%d\n", min , max);
  * @endcode
  * @param[in]  ys       yang-stmt, leaf or leaf-list
- * @param[out] origtype original type may be derived or built-in
+ * @param[out] origtype original type may be derived or built-in (malloced)
  * @param[out] yrestype Resolved type. return built-in type or NULL. 
  * @param[out] options  Flags field of optional values, see YANG_OPTIONS_*
  * @param[out] cvv      Cvec with min/max range or length. 
@@ -1465,19 +1467,23 @@ yang_type_get(yang_stmt    *ys,
 {
     int retval = -1;
     yang_stmt    *ytype;        /* type */
-    char         *type;
+    char         *type = NULL;
 
     if (options)
 	*options = 0x0;
     /* Find mandatory type */
     if ((ytype = yang_find(ys, Y_TYPE, NULL)) == NULL){
-	clicon_err(OE_DB, 0, "mandatory type object is not found");
+	clicon_err(OE_DB, ENOENT, "mandatory type object is not found");
 	goto done;
     }
     /* XXX: here we seem to have some problems if type is union */
-    type = yarg_id(ytype);
-    if (origtype)
-	*origtype = type;
+    if (nodeid_split(yang_argument_get(ytype), NULL, &type) < 0)
+	goto done;
+    if (origtype &&
+	(*origtype = strdup(type)) == NULL){
+	clicon_err(OE_XML, errno, "stdup");
+	goto done;
+    }
     if (yang_type_resolve(ys, ys, ytype, yrestype, 
 			  options, cvv, patterns, regexps, fraction) < 0)
 	goto done;
@@ -1485,6 +1491,8 @@ yang_type_get(yang_stmt    *ys,
 		 *yrestype?(*yrestype)->ys_argument:"null");
     retval = 0;
   done:
+    if (type)
+	free(type);
     return retval;
 }
 
@@ -1496,16 +1504,18 @@ yang_type2cv(yang_stmt  *ys)
 {
     yang_stmt      *yrestype;  /* resolved type */
     char           *restype;  /* resolved type */
-    char           *type;   /* original type */
+    char           *origtype=NULL;   /* original type */
     enum cv_type    cvtype = CGV_ERR;
     
     /* Find type specification */
-    if (yang_type_get(ys, &type, &yrestype, NULL, NULL, NULL, NULL, NULL)
+    if (yang_type_get(ys, &origtype, &yrestype, NULL, NULL, NULL, NULL, NULL)
  < 0)
 	goto done;
     restype = yrestype?yrestype->ys_argument:NULL;
-    if (clicon_type2cv(type, restype, ys, &cvtype) < 0) /* This handles non-resolved also */
+    if (clicon_type2cv(origtype, restype, ys, &cvtype) < 0) /* This handles non-resolved also */
 	goto done;
  done:
+    if (origtype)
+	free(origtype);
     return cvtype;
 }
diff --git a/test/test_identity.sh b/test/test_identity.sh
index 81f956e5..b8005d97 100755
--- a/test/test_identity.sh
+++ b/test/test_identity.sh
@@ -226,7 +226,7 @@ new "Netconf set undefined acl-type"
 expecteof "$clixon_netconf -qf $cfg" 0 '<rpc><edit-config><target><candidate/></target><config><acls xmlns="urn:example:my-crypto"><acl><name>x</name><type>undefined</type></acl></acls></config></edit-config></rpc>]]>]]>' '^<rpc-reply><ok/></rpc-reply>]]>]]>$'
 
 new "netconf validate fail"
-expecteof "$clixon_netconf -qf $cfg" 0 "<rpc><validate><source><candidate/></source></validate></rpc>]]>]]>" '^<rpc-reply><rpc-error><error-type>application</error-type><error-tag>operation-failed</error-tag><error-severity>error</error-severity><error-message>Identityref validation failed, mc:undefined not derived from acl-base</error-message></rpc-error></rpc-reply>]]>]]>'
+expecteof "$clixon_netconf -qf $cfg" 0 "<rpc><validate><source><candidate/></source></validate></rpc>]]>]]>" '^<rpc-reply><rpc-error><error-type>application</error-type><error-tag>operation-failed</error-tag><error-severity>error</error-severity><error-message>Identityref validation failed, undefined not derived from acl-base</error-message></rpc-error></rpc-reply>]]>]]>'
 
 new "netconf discard-changes"
 expecteof "$clixon_netconf -qf $cfg" 0 "<rpc><discard-changes/></rpc>]]>]]>" "^<rpc-reply><ok/></rpc-reply>]]>]]>$"