Changeset 400 for draft-ietf-httpbis/latest/p1-messaging.xml

Timestamp:

Nov 15, 2008, 11:45:44 AM (11 years ago)

Author:

julian.reschke@…

Message:

rewrite definition of list rule, deprecate empty list elements (related to #36)

File:

• draft-ietf-httpbis/latest/p1-messaging.xml (modified) (3 diffs)

draft-ietf-httpbis/latest/p1-messaging.xml

@@ -347 +347 @@
     A construct "#" is defined, similar to "*", for defining lists of
     elements. The full form is "<n>#<m>element" indicating at least
-    <n> and at most <m> elements, each separated by one or more commas
-    (",") and &OPTIONAL; linear white space (OWS). This makes the usual
-    form of lists very easy; a rule such as
-    <figure><artwork type="example">
- ( *<x:ref>OWS</x:ref> element *( *<x:ref>OWS</x:ref> "," *<x:ref>OWS</x:ref> element ))</artwork></figure>
+    &lt;n&gt; and at most &lt;m&gt; elements, each separated by a single comma
+    (",") and optional whitespace (OWS).   
   </t>
+  <figure><preamble>
+    Thus,
+</preamble><artwork type="example">
+  1#element =&gt; element *( OWS "," OWS element )
+</artwork></figure>
+  <figure><preamble>
+    and:
+</preamble><artwork type="example">
+  #element =&gt; [ 1#element ]
+</artwork></figure>
+  <figure><preamble>
+    and for n &gt;= 1 and m &gt; 1:
+</preamble><artwork type="example">
+  &lt;n&gt;#&lt;m&gt;element =&gt; element &lt;n-1&gt;*&lt;m-1&gt;( OWS "," OWS element )
+</artwork></figure>
   <t>
-    can be shown as
-    <figure><artwork type="example">
- 1#element</artwork></figure>
+    For compatibility with legacy list rules, recipients &SHOULD; accept empty
+    list elements. In other words, consumers would follow the list productions:
   </t>
-  <t>
-    Wherever this construct is used, null elements are allowed, but do
-    not contribute to the count of elements present. That is,
-    "(element), , (element) " is permitted, but counts as only two
-    elements. Therefore, where at least one element is required, at
-    least one non-null element &MUST; be present. Default values are 0
-    and infinity so that "#element" allows any number, including zero;
-    "1#element" requires at least one; and "1#2element" allows one or
-    two.
-  </t>
+<figure><artwork type="example">
+#element =&gt; [ ( "," / element ) *( OWS "," [ OWS element ] ) ]
+
+1#element =&gt; *( "," OWS ) element *( OWS "," [ OWS element ] )
+</artwork></figure>  
   <t>
     <cref anchor="abnf.list">
@@ -4082 +4088 @@
 <section title="Changes from RFC 2616" anchor="changes.from.rfc.2616">
 <t>
+  Empty list elements in list productions have been deprecated.
+  (<xref target="notation.abnf"/>)
+</t>
+<t>
   Rules about implicit linear white space between certain grammar productions
   have been removed; now it's only allowed when specifically pointed out
@@ -4696 +4706 @@
 </t>
 <t>
+  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
+  <list style="symbols"> 
+    <t>
+      Rewrite definition of list rules, deprecate empty list elements.
+    </t>
+  </list>
+</t>
+<t>
   Other changes:
   <list style="symbols">