diff -r 2d50e7e2a2bd lib/string/abstract_string.li
--- a/lib/string/abstract_string.li	Sun Aug 31 01:37:20 2008 +0200
+++ b/lib/string/abstract_string.li	Sun Aug 31 11:43:29 2008 +0200
@@ -271,7 +271,18 @@
   - has_substring other:ABSTRACT_STRING :BOOLEAN <-
   // True if `other' is in the STRING.
   ( first_substring_index other != 0 );
-    
+
+  - occurrences_string s:ABSTRACT_STRING :INTEGER <-
+  // Number of times character `c' appears in the string.
+  ( + n, i :INTEGER;
+    i := first_substring_index s;
+    { i != 0 }.while_do {
+      n := n + 1;
+      i := substring_index (s, i);
+    };
+    n
+  );
+
   - occurrences c:CHARACTER :INTEGER <-
   // Number of times character `c' appears in the string.
   (
diff -r 2d50e7e2a2bd src/parser.li
--- a/src/parser.li	Sun Aug 31 01:37:20 2008 +0200
+++ b/src/parser.li	Sun Aug 31 11:43:29 2008 +0200
@@ -487,7 +487,7 @@
     result
   );  
     
-  //-- cap_identifier -> 'A'-'Z' {'A'-'Z' | '0'-'9' | '_'}
+  //-- cap_identifier -> 'A'-'Z' {'A'-'Z' | '0'-'9' | '_' | ':'}
   - read_cap_identifier:BOOLEAN <-
   ( + posold,idx:INTEGER;
     + result:BOOLEAN;
@@ -502,7 +502,8 @@
 	{
 	  (! last_character.is_upper) && 
 	  {! last_character.is_digit} &&
-	  {last_character != '_'}
+	  {last_character != '_'} &&
+	  {last_character != ':'}
 	}
       }.until_do {
 	string_tmp.add_last last_character;
@@ -510,9 +511,22 @@
       };
       (! string_tmp.is_empty).if {
 	idx := string_tmp.first_substring_index "__";
-	(idx != 0).if { 
+	(idx != 0).if {
 	  position := posold + idx;
-	  syntax_error (current_position,"Identifier is incorrect.");
+	  syntax_error (current_position,"Identifier is incorrect (__ is not allowed).");
+	};
+	idx := string_tmp.first_substring_index ":::";
+	(idx != 0).if {
+	  position := posold + idx;
+	  syntax_error (current_position,"Identifier is incorrect (::: is not allowed).");
+	};
+	(string_tmp.last = ':').if {
+	  position := posold + string_tmp.count;
+	  syntax_error (current_position,"Identifier is incorrect (: is not allowed at the very end).");
+	};
+	(sring_tmp.occurrences_string "" > 1).if {
+	  position := posold;
+	  syntax_error (current_position,"Identifier is incorrect (:: is allowed only once).");
 	};
 	last_string := ALIAS_STR.get string_tmp;
 	result := TRUE;