CVS difference for ais/ai-00153.txt

--- ais/ai-00153.txt	1998/09/30 00:17:27	1.1
+++ ais/ai-00153.txt	1999/03/22 23:42:39	1.2
@@ -1,24 +1,62 @@
-!standard F.3.1    (04)                               96-09-04  AI95-00153/00
+!standard F.3.1 (04-38)                               99-03-21  AI95-00153/01
+!standard F.3.1 (01)
+!standard F.3.1 (43)
 !class binding interpretation 96-09-04
+!status work item 99-03-21
 !status received 96-09-04
 !priority Medium
 !difficulty Medium
 !subject Picture String Grammar or Composition Rules Need Tightening
 
-!summary 96-09-04
+!summary 99-03-21
 
+    Picture strings such as "++++>" are not well formed.
 
-!question 96-09-04
+!question 99-03-21
 
+The String "++++>" and like Strings with '>' unmatched by any '<' appear to
+be valid picture strings based on the following
+production sequence:
 
-!recommendation 96-09-04
+    picture string ::= ... | non_currency_picture_string
+    non_currency_picture_string ::= all_sign_number | ...
+    all_sign_number             ::= all_sign_fore [...] [>]
+    all_sign_fore               ::= sign_char {...}
+                  sign_char {sign_char | ...}
+    sign_char                   ::= + | - | <
 
+    Is the picture string "++++>" well formed? (No.)
 
-!wording 96-09-04
+!recommendation 99-03-21
 
+ A '>' character can only appear in an all_sign_number if it
+contains '<' characters.
 
-!discussion 96-09-04
+!wording 99-03-21
 
+Extend F.3.1(43) to read:
+
+"If a picture String has '+' or '-' as fixed_LHS_sign, in a
+floating_LHS_sign or in an all_sign_number, then it has no
+RHS_sign {or '>' character}."
+
+!discussion 99-03-21
+
+The problem is that the production for all_sign_number does not use the
+RHS_sign production, it contains the literal '>'. This is what comes of
+trying to fold the picture string grammar and composition constraints into
+as few words as possible.  Some of the composition constraints are could
+have been included in a context free grammar but at the expense of making
+it much longer, and more difficult to read.  However, in the case of
+all_sign_number and F.3.1(43) we compressed a little too hard.  If this
+paragraph is written as two rules, it is much easier to read--and is even
+correct:
+
+If a picture String has '+' or '-' as fixed_LHS_sign or in a
+floating_LHS_sign then it has no RHS_sign. If an all_sign_number contains
+'+' or '-' characters then it does not end in a '>' character.
+
+In fact this might be a better way to correct the wording.
 
 !appendix 96-09-04