diff --git a/Makefile b/Makefile
index f439d7645..e0decbfe7 100644
--- a/Makefile
+++ b/Makefile
@@ -88,7 +88,7 @@ $(bd)/%.abnf: %.xml lib/extract-artwork.xslt
 	$(saxon) $< lib/xreffer.xslt | $(saxon) - lib/extract-artwork.xslt type="abnf7230" >$@
 
 $(bd)/%.parsed-abnf: $(bd)/%.abnf
-	$(bap)/bap -i $(bap)/core.abnf -X rfc7405 < $< | LC_COLLATE=C sort | $(bap)/bap -k -i $(bap)/core.abnf -X rfc7405 -l 69 >$@
+	$(bap)/bap -i $(bap)/core.abnf -L1 -X rfc7405 < $< | LC_COLLATE=C sort | $(bap)/bap -k -i $(bap)/core.abnf -L1 -X rfc7405 -l 69 >$@
 
 $(bd)/%.abnf-appendix: $(bd)/%.parsed-abnf
 	$(saxon) $*.xml lib/abnf2xml2rfc.xslt abnf="../$<" >$@
diff --git a/bap/main.c b/bap/main.c
index 3aadaf1b7..39dca421d 100644
--- a/bap/main.c
+++ b/bap/main.c
@@ -114,6 +114,7 @@ int qflag = 0;		/* quiet */
 int canon = 1;		/* canonify */
 int asxml = 0;    /* output XML */
 int olenlimit = 0;   /* 0 for unlimited, might be any other value */
+int listrulex = 0;   /* 0 for RFC 7320-style, 1 for 2019 experimental */
 
 int yyparse(void);
 
@@ -122,7 +123,7 @@ usage(void)
 {
   fprintf(stderr, "Bill's ABNF Parser version %s\n", versionstring);
   fprintf(stderr, " (with extensions from <https://svn.tools.ietf.org/svn/wg/httpbis/abnfparser/bap/>)\n", versionstring);
-  fprintf(stderr, "usage: bap [-cknqtx][-i rules][-l num][-S name][-X ext][file]\n");
+  fprintf(stderr, "usage: bap [-cknqtx][-i rules][-l num][-L rtyp][-S name][-X ext][file]\n");
   fprintf(stderr, " parse ABNF grammar from file or stdin\n");
   fprintf(stderr, " Input options:\n");
   fprintf(stderr, "  -c       include rule definition line # in comment\n");
@@ -133,6 +134,7 @@ usage(void)
   fprintf(stderr, " Output options:\n");
   fprintf(stderr, "  -k       add comments for printable characters specified as %%x\n");
   fprintf(stderr, "  -l num   limit the length of each line to \"num\" characters\n");
+  fprintf(stderr, "  -L rtyp  how to expand #list production (0 == 2014, 1 == 2019)\n");
   fprintf(stderr, "  -n       don't \"canonify\" result\n");
   fprintf(stderr, "  -q       don't print parsed grammar\n");
   fprintf(stderr, "  -t       include type info in result\n");
@@ -155,7 +157,7 @@ main(int argc, char **argv)
 #endif
   hcreate(MAXRULE);
 
-  while ((ch = getopt(argc, argv, "cdi:kntqS:xl:X:")) != -1) {
+  while ((ch = getopt(argc, argv, "cdi:kntqS:xl:L:X:")) != -1) {
     switch (ch) {
     case 'c':
       cflag++;
@@ -224,6 +226,14 @@ main(int argc, char **argv)
       olenlimit = atoi(optarg);
       break;
 
+    case 'L':
+      listrulex = atoi(optarg);
+      if (listrulex != 0 && listrulex != 1) {
+        fprintf(stderr, "-L: illegal argument %d\n", listrulex);
+        exit(2);
+      }
+      break;
+
     default:
       usage();
     }
@@ -416,6 +426,61 @@ printobjasxml(object *o, int indent)
  */
 #define NOBRACKET(o)	((o->next == NULL) && (o->u.e.repetition.lo == 0))
 
+// code to emit #rule (RFC 7230)
+static void
+p_listrule_rfc7230(object *o)
+{
+  if (o->u.e.repetition.lo == 0) {
+    local_printf("[ ( \",\" / ");
+    if (o->u.e.e.rule.rule) {
+      local_printf("%s", o->u.e.e.rule.rule->name);
+      o->u.e.e.rule.rule->used = 1;
+    } else {
+      local_printf("%s", o->u.e.e.rule.name);
+    }
+    local_printf(" ) *( OWS \",\" [ OWS ");
+    local_printf("%s", (o->u.e.e.rule.rule) ?
+      o->u.e.e.rule.rule->name :
+      o->u.e.e.rule.name);
+      local_printf(" ] ) ]");
+  } else if (o->u.e.repetition.lo == 1) {
+    local_printf(" *( \",\" OWS ) ");
+    if (o->u.e.e.rule.rule) {
+      local_printf("%s", o->u.e.e.rule.rule->name);
+      o->u.e.e.rule.rule->used = 1;
+    } else {
+      local_printf("%s", o->u.e.e.rule.name);
+    }
+    local_printf(" *( OWS \",\" [ OWS ");
+    local_printf("%s", (o->u.e.e.rule.rule) ?
+      o->u.e.e.rule.rule->name :
+      o->u.e.e.rule.name);
+    local_printf(" ] )");
+  }
+  else {
+    local_printf("TODO: something is wrong");
+  }
+}
+
+// code to emit #rule (2019)
+// #element =&gt; *( OWS "," ) *( [ OWS element ] OWS "," )
+static void
+p_listrule_2019(object *o)
+{
+  local_printf("[ ");
+  if (o->u.e.e.rule.rule) {
+    local_printf("%s", o->u.e.e.rule.rule->name);
+    o->u.e.e.rule.rule->used = 1;
+  } else {
+    local_printf("%s", o->u.e.e.rule.name);
+  }
+  local_printf(" ] *( OWS \",\" OWS [ ");
+  local_printf("%s", (o->u.e.e.rule.rule) ?
+    o->u.e.e.rule.rule->name :
+    o->u.e.e.rule.name);
+  local_printf(" ] )");
+}
+
 static void
 printobj_r(object *o, int parenttype, int tflag)
 {
@@ -441,38 +506,13 @@ printobj_r(object *o, int parenttype, int tflag)
       break;
     case T_RULE: /* identation to delimit the code change */
       if (tflag)
-	local_printf("{RULE}");
+      local_printf("{RULE}");
       if (o->u.e.islist) {
-	if (o->u.e.repetition.lo == 0) {
-	  local_printf("[ ( \",\" / ");
-	  if (o->u.e.e.rule.rule) {
-	    local_printf("%s", o->u.e.e.rule.rule->name);
-	    o->u.e.e.rule.rule->used = 1;
-	  } else {
-	    local_printf("%s", o->u.e.e.rule.name);
-	  }
-	  local_printf(" ) *( OWS \",\" [ OWS ");
-	  local_printf("%s", (o->u.e.e.rule.rule) ? 
-		 o->u.e.e.rule.rule->name : 
-		 o->u.e.e.rule.name);
-	  local_printf(" ] ) ]");
-	} else if (o->u.e.repetition.lo == 1) {
-	  local_printf(" *( \",\" OWS ) ");
-	  if (o->u.e.e.rule.rule) {
-	    local_printf("%s", o->u.e.e.rule.rule->name);
-	    o->u.e.e.rule.rule->used = 1;
-	  } else {
-	    local_printf("%s", o->u.e.e.rule.name);
-	  }
-	  local_printf(" *( OWS \",\" [ OWS ");
-	  local_printf("%s", (o->u.e.e.rule.rule) ? 
-		 o->u.e.e.rule.rule->name : 
-		 o->u.e.e.rule.name);
-	  local_printf(" ] )");
-	}
-	else {
-	  local_printf("TODO: something is wrong");
-	} 
+        if (listrulex == 0) {
+          p_listrule_rfc7230(o);
+        } else {
+          p_listrule_2019(o);
+        }
       } else {
 	printrep(&o->u.e.repetition);
 	if (o->u.e.e.rule.rule) {
diff --git a/draft-ietf-httpbis-cache-latest.html b/draft-ietf-httpbis-cache-latest.html
index a04f8d142..f2cc51062 100644
--- a/draft-ietf-httpbis-cache-latest.html
+++ b/draft-ietf-httpbis-cache-latest.html
@@ -2438,8 +2438,8 @@ <h2 id="rfc.section.A" class="np"><a href="#rfc.section.A">Appendix A.</a>&nbsp;
          </div>
          <div id="rfc.section.A.p.2"><pre class="inline prettyprint lang-ietf_abnf"><a href="#header.age" class="smpl">Age</a> = delta-seconds
 
-<a href="#header.cache-control" class="smpl">Cache-Control</a> = *( "," OWS ) cache-directive *( OWS "," [ OWS
- cache-directive ] )
+<a href="#header.cache-control" class="smpl">Cache-Control</a> = [ cache-directive ] *( OWS "," OWS [ cache-directive
+ ] )
 
 <a href="#header.expires" class="smpl">Expires</a> = HTTP-date
 
diff --git a/draft-ietf-httpbis-cache-latest.xml b/draft-ietf-httpbis-cache-latest.xml
index 2cdbaa2ef..568b941a3 100644
--- a/draft-ietf-httpbis-cache-latest.xml
+++ b/draft-ietf-httpbis-cache-latest.xml
@@ -2199,8 +2199,8 @@
 <section xmlns:x="http://purl.org/net/xml2rfc/ext" title="Collected ABNF" anchor="collected.abnf"><t>In the collected ABNF below, list rules are expanded as per <xref target="Semantics" x:rel="#abnf.extension"/>.</t><sourcecode type="abnf" name="draft-ietf-httpbis-cache-latest.parsed-abnf">
 <x:ref>Age</x:ref> = delta-seconds
 
-<x:ref>Cache-Control</x:ref> = *( "," OWS ) cache-directive *( OWS "," [ OWS
- cache-directive ] )
+<x:ref>Cache-Control</x:ref> = [ cache-directive ] *( OWS "," OWS [ cache-directive
+ ] )
 
 <x:ref>Expires</x:ref> = HTTP-date
 
diff --git a/draft-ietf-httpbis-messaging-latest.html b/draft-ietf-httpbis-messaging-latest.html
index b777830a2..41cde1cde 100644
--- a/draft-ietf-httpbis-messaging-latest.html
+++ b/draft-ietf-httpbis-messaging-latest.html
@@ -2909,8 +2909,8 @@ <h2 id="rfc.section.A" class="np"><a href="#rfc.section.A">Appendix A.</a>&nbsp;
          </div>
          <div id="rfc.section.A.p.2"><pre class="inline prettyprint lang-ietf_abnf"><a href="draft-ietf-httpbis-semantics-latest.html#whitespace" class="smpl">BWS</a> = &lt;BWS, see <a href="#Semantics" id="rfc.xref.Semantics.55"><cite title="HTTP Semantics">[Semantics]</cite></a>, <a href="draft-ietf-httpbis-semantics-latest.html#rfc.section.4.3">Section 4.3</a>&gt;
 
-<a href="#header.connection" class="smpl">Connection</a> = *( "," OWS ) connection-option *( OWS "," [ OWS
- connection-option ] )
+<a href="#header.connection" class="smpl">Connection</a> = [ connection-option ] *( OWS "," OWS [ connection-option
+ ] )
 
 <a href="#message.format" class="smpl">HTTP-message</a> = start-line *( header-field CRLF ) CRLF [ message-body
  ]
@@ -2921,11 +2921,11 @@ <h2 id="rfc.section.A" class="np"><a href="#rfc.section.A">Appendix A.</a>&nbsp;
 
 <a href="draft-ietf-httpbis-semantics-latest.html#whitespace" class="smpl">RWS</a> = &lt;RWS, see <a href="#Semantics" id="rfc.xref.Semantics.57"><cite title="HTTP Semantics">[Semantics]</cite></a>, <a href="draft-ietf-httpbis-semantics-latest.html#rfc.section.4.3">Section 4.3</a>&gt;
 
-<a href="#header.te" class="smpl">TE</a> = [ ( "," / t-codings ) *( OWS "," [ OWS t-codings ] ) ]
-<a href="#header.transfer-encoding" class="smpl">Transfer-Encoding</a> = *( "," OWS ) transfer-coding *( OWS "," [ OWS
+<a href="#header.te" class="smpl">TE</a> = [ t-codings ] *( OWS "," OWS [ t-codings ] )
+<a href="#header.transfer-encoding" class="smpl">Transfer-Encoding</a> = [ transfer-coding ] *( OWS "," OWS [
  transfer-coding ] )
 
-<a href="#header.upgrade" class="smpl">Upgrade</a> = *( "," OWS ) protocol *( OWS "," [ OWS protocol ] )
+<a href="#header.upgrade" class="smpl">Upgrade</a> = [ protocol ] *( OWS "," OWS [ protocol ] )
 
 <a href="#imported.rules" class="smpl">absolute-URI</a> = &lt;absolute-URI, see <a href="#RFC3986" id="rfc.xref.RFC3986.6"><cite title="Uniform Resource Identifier (URI): Generic Syntax">[RFC3986]</cite></a>, <a href="https://tools.ietf.org/html/rfc3986#section-4.3">Section 4.3</a>&gt;
 <a href="#absolute-form" class="smpl">absolute-form</a> = absolute-URI
diff --git a/draft-ietf-httpbis-messaging-latest.xml b/draft-ietf-httpbis-messaging-latest.xml
index c4d0658db..963c929f5 100644
--- a/draft-ietf-httpbis-messaging-latest.xml
+++ b/draft-ietf-httpbis-messaging-latest.xml
@@ -3007,8 +3007,8 @@ Upgrade: HTTP/2.0
 <section xmlns:x="http://purl.org/net/xml2rfc/ext" title="Collected ABNF" anchor="collected.abnf"><t>In the collected ABNF below, list rules are expanded as per <xref target="Semantics" x:rel="#abnf.extension"/>.</t><sourcecode type="abnf" name="draft-ietf-httpbis-messaging-latest.parsed-abnf">
 <x:ref>BWS</x:ref> = &lt;BWS, see <xref target="Semantics" x:fmt="," x:sec="4.3"/>&gt;
 
-<x:ref>Connection</x:ref> = *( "," OWS ) connection-option *( OWS "," [ OWS
- connection-option ] )
+<x:ref>Connection</x:ref> = [ connection-option ] *( OWS "," OWS [ connection-option
+ ] )
 
 <x:ref>HTTP-message</x:ref> = start-line *( header-field CRLF ) CRLF [ message-body
  ]
@@ -3019,11 +3019,11 @@ Upgrade: HTTP/2.0
 
 <x:ref>RWS</x:ref> = &lt;RWS, see <xref target="Semantics" x:fmt="," x:sec="4.3"/>&gt;
 
-<x:ref>TE</x:ref> = [ ( "," / t-codings ) *( OWS "," [ OWS t-codings ] ) ]
-<x:ref>Transfer-Encoding</x:ref> = *( "," OWS ) transfer-coding *( OWS "," [ OWS
+<x:ref>TE</x:ref> = [ t-codings ] *( OWS "," OWS [ t-codings ] )
+<x:ref>Transfer-Encoding</x:ref> = [ transfer-coding ] *( OWS "," OWS [
  transfer-coding ] )
 
-<x:ref>Upgrade</x:ref> = *( "," OWS ) protocol *( OWS "," [ OWS protocol ] )
+<x:ref>Upgrade</x:ref> = [ protocol ] *( OWS "," OWS [ protocol ] )
 
 <x:ref>absolute-URI</x:ref> = &lt;absolute-URI, see <xref target="RFC3986" x:fmt="," x:sec="4.3"/>&gt;
 <x:ref>absolute-form</x:ref> = absolute-URI
diff --git a/draft-ietf-httpbis-semantics-latest.html b/draft-ietf-httpbis-semantics-latest.html
index 5e770c751..7d41dcd5b 100644
--- a/draft-ietf-httpbis-semantics-latest.html
+++ b/draft-ietf-httpbis-semantics-latest.html
@@ -8633,39 +8633,41 @@ <h2 id="rfc.section.11"><a href="#rfc.section.11">11.</a>&nbsp;<a href="#abnf.ex
          <div id="rfc.section.11.p.8"><pre class="text">  &lt;n&gt;#&lt;m&gt;element =&gt; element &lt;n-1&gt;*&lt;m-1&gt;( OWS "," OWS element )
 </pre></div>
          <div id="rfc.section.11.p.9" class="avoidbreakafter">
-            <p>For compatibility with legacy list rules, a recipient <em class="bcp14">MUST</em> parse and ignore a reasonable number of empty list elements: enough to handle common
+            <p>Empty elements do not contribute to the count of elements present. A recipient <em class="bcp14">MUST</em> parse and ignore a reasonable number of empty list elements: enough to handle common
                mistakes by senders that merge values, but not so much that they could be used as
                a denial-of-service mechanism. In other words, a recipient <em class="bcp14">MUST</em> accept lists that satisfy the following syntax:<a class="self" href="#rfc.section.11.p.9">¶</a></p>
          </div>
-         <div id="rfc.section.11.p.10"><pre class="text">  #element =&gt; [ ( "," / element ) *( OWS "," [ OWS element ] ) ]
-  
-  1#element =&gt; *( "," OWS ) element *( OWS "," [ OWS element ] )
+         <div id="rfc.section.11.p.10"><pre class="text">  #element =&gt; [ element ] *( OWS "," OWS [ element ] )
 </pre></div>
-         <div id="rfc.section.11.p.11" class="avoidbreakafter">
-            <p>Empty elements do not contribute to the count of elements present. For example, given
-               these ABNF productions:<a class="self" href="#rfc.section.11.p.11">¶</a></p>
+         <div id="rfc.section.11.p.11">
+            <p>Note that because of the potential presence of empty list elements, the RFC 5234 ABNF
+               cannot enforce the cardinality of list elements, and consequently all cases are mapped
+               is if there was no cardinality specified.<a class="self" href="#rfc.section.11.p.11">¶</a></p>
+         </div>
+         <div id="rfc.section.11.p.12" class="avoidbreakafter">
+            <p>For example, given these ABNF productions:<a class="self" href="#rfc.section.11.p.12">¶</a></p>
          </div>
-         <div id="rfc.section.11.p.12"><pre class="text">  example-list      = 1#example-list-elmt
+         <div id="rfc.section.11.p.13"><pre class="text">  example-list      = 1#example-list-elmt
   example-list-elmt = token ; see <a href="#field.components" title="Header Field Value Components">Section&nbsp;4.2.3</a> 
 </pre></div>
-         <div id="rfc.section.11.p.13" class="avoidbreakafter">
+         <div id="rfc.section.11.p.14" class="avoidbreakafter">
             <p>Then the following are valid values for example-list (not including the double quotes,
-               which are present for delimitation only):<a class="self" href="#rfc.section.11.p.13">¶</a></p>
+               which are present for delimitation only):<a class="self" href="#rfc.section.11.p.14">¶</a></p>
          </div>
-         <div id="rfc.section.11.p.14"><pre class="text">  "foo,bar"
+         <div id="rfc.section.11.p.15"><pre class="text">  "foo,bar"
   "foo ,bar,"
   "foo , ,bar,charlie"
 </pre></div>
-         <div id="rfc.section.11.p.15" class="avoidbreakafter">
+         <div id="rfc.section.11.p.16" class="avoidbreakafter">
             <p>In contrast, the following values would be invalid, since at least one non-empty element
-               is required by the example-list production:<a class="self" href="#rfc.section.11.p.15">¶</a></p>
+               is required by the example-list production:<a class="self" href="#rfc.section.11.p.16">¶</a></p>
          </div>
-         <div id="rfc.section.11.p.16"><pre class="text">  ""
+         <div id="rfc.section.11.p.17"><pre class="text">  ""
   ","
   ",   ,"
 </pre></div>
-         <div id="rfc.section.11.p.17">
-            <p><a href="#collected.abnf" title="Collected ABNF">Appendix&nbsp;A</a> shows the collected ABNF for recipients after the list constructs have been expanded.<a class="self" href="#rfc.section.11.p.17">¶</a></p>
+         <div id="rfc.section.11.p.18">
+            <p><a href="#collected.abnf" title="Collected ABNF">Appendix&nbsp;A</a> shows the collected ABNF for recipients after the list constructs have been expanded.<a class="self" href="#rfc.section.11.p.18">¶</a></p>
          </div>
       </section>
       <section id="security.considerations">
@@ -9420,17 +9422,16 @@ <h2 id="rfc.section.A" class="np"><a href="#rfc.section.A">Appendix A.</a>&nbsp;
 <a href="#header.accept-language" class="smpl">Accept-Language</a> = *( "," OWS ) ( language-range [ weight ] ) *( OWS
  "," [ OWS ( language-range [ weight ] ) ] )
 <a href="#header.accept-ranges" class="smpl">Accept-Ranges</a> = acceptable-ranges
-<a href="#header.allow" class="smpl">Allow</a> = [ ( "," / method ) *( OWS "," [ OWS method ] ) ]
-<a href="#header.authentication-info" class="smpl">Authentication-Info</a> = [ ( "," / auth-param ) *( OWS "," [ OWS
- auth-param ] ) ]
+<a href="#header.allow" class="smpl">Allow</a> = [ method ] *( OWS "," OWS [ method ] )
+<a href="#header.authentication-info" class="smpl">Authentication-Info</a> = [ auth-param ] *( OWS "," OWS [ auth-param ] )
 <a href="#header.authorization" class="smpl">Authorization</a> = credentials
 
 <a href="#whitespace" class="smpl">BWS</a> = OWS
 
-<a href="#header.content-encoding" class="smpl">Content-Encoding</a> = *( "," OWS ) content-coding *( OWS "," [ OWS
- content-coding ] )
-<a href="#header.content-language" class="smpl">Content-Language</a> = *( "," OWS ) language-tag *( OWS "," [ OWS
- language-tag ] )
+<a href="#header.content-encoding" class="smpl">Content-Encoding</a> = [ content-coding ] *( OWS "," OWS [ content-coding
+ ] )
+<a href="#header.content-language" class="smpl">Content-Language</a> = [ language-tag ] *( OWS "," OWS [ language-tag ]
+ )
 <a href="#header.content-length" class="smpl">Content-Length</a> = 1*DIGIT
 <a href="#header.content-location" class="smpl">Content-Location</a> = absolute-URI / partial-URI
 <a href="#header.content-range" class="smpl">Content-Range</a> = byte-content-range / other-content-range
@@ -9449,11 +9450,10 @@ <h2 id="rfc.section.A" class="np"><a href="#rfc.section.A">Appendix A.</a>&nbsp;
 <a href="#header.host" class="smpl">Host</a> = uri-host [ ":" port ]
 
 <a href="#preferred.date.format" class="smpl">IMF-fixdate</a> = day-name "," SP date1 SP time-of-day SP GMT
-<a href="#header.if-match" class="smpl">If-Match</a> = "*" / ( *( "," OWS ) entity-tag *( OWS "," [ OWS
- entity-tag ] ) )
+<a href="#header.if-match" class="smpl">If-Match</a> = "*" / ( [ entity-tag ] *( OWS "," OWS [ entity-tag ] ) )
 <a href="#header.if-modified-since" class="smpl">If-Modified-Since</a> = HTTP-date
-<a href="#header.if-none-match" class="smpl">If-None-Match</a> = "*" / ( *( "," OWS ) entity-tag *( OWS "," [ OWS
- entity-tag ] ) )
+<a href="#header.if-none-match" class="smpl">If-None-Match</a> = "*" / ( [ entity-tag ] *( OWS "," OWS [ entity-tag ]
+ ) )
 <a href="#header.if-range" class="smpl">If-Range</a> = entity-tag / HTTP-date
 <a href="#header.if-unmodified-since" class="smpl">If-Unmodified-Since</a> = HTTP-date
 
@@ -9464,10 +9464,9 @@ <h2 id="rfc.section.A" class="np"><a href="#rfc.section.A">Appendix A.</a>&nbsp;
 
 <a href="#whitespace" class="smpl">OWS</a> = *( SP / HTAB )
 
-<a href="#header.proxy-authenticate" class="smpl">Proxy-Authenticate</a> = *( "," OWS ) challenge *( OWS "," [ OWS
- challenge ] )
-<a href="#header.proxy-authentication-info" class="smpl">Proxy-Authentication-Info</a> = [ ( "," / auth-param ) *( OWS "," [ OWS
- auth-param ] ) ]
+<a href="#header.proxy-authenticate" class="smpl">Proxy-Authenticate</a> = [ challenge ] *( OWS "," OWS [ challenge ] )
+<a href="#header.proxy-authentication-info" class="smpl">Proxy-Authentication-Info</a> = [ auth-param ] *( OWS "," OWS [
+ auth-param ] )
 <a href="#header.proxy-authorization" class="smpl">Proxy-Authorization</a> = credentials
 
 <a href="#whitespace" class="smpl">RWS</a> = 1*( SP / HTAB )
@@ -9477,26 +9476,24 @@ <h2 id="rfc.section.A" class="np"><a href="#rfc.section.A">Appendix A.</a>&nbsp;
 
 <a href="#header.server" class="smpl">Server</a> = product *( RWS ( product / comment ) )
 
-<a href="#header.trailer" class="smpl">Trailer</a> = *( "," OWS ) field-name *( OWS "," [ OWS field-name ] )
+<a href="#header.trailer" class="smpl">Trailer</a> = [ field-name ] *( OWS "," OWS [ field-name ] )
 
 <a href="#uri" class="smpl">URI-reference</a> = &lt;URI-reference, see <a href="#RFC3986" id="rfc.xref.RFC3986.25"><cite title="Uniform Resource Identifier (URI): Generic Syntax">[RFC3986]</cite></a>, <a href="https://tools.ietf.org/html/rfc3986#section-4.1">Section 4.1</a>&gt;
 <a href="#header.user-agent" class="smpl">User-Agent</a> = product *( RWS ( product / comment ) )
 
-<a href="#header.vary" class="smpl">Vary</a> = "*" / ( *( "," OWS ) field-name *( OWS "," [ OWS field-name ]
- ) )
+<a href="#header.vary" class="smpl">Vary</a> = "*" / ( [ field-name ] *( OWS "," OWS [ field-name ] ) )
 <a href="#header.via" class="smpl">Via</a> = *( "," OWS ) ( received-protocol RWS received-by [ RWS comment
  ] ) *( OWS "," [ OWS ( received-protocol RWS received-by [ RWS
  comment ] ) ] )
 
-<a href="#header.www-authenticate" class="smpl">WWW-Authenticate</a> = *( "," OWS ) challenge *( OWS "," [ OWS challenge
- ] )
+<a href="#header.www-authenticate" class="smpl">WWW-Authenticate</a> = [ challenge ] *( OWS "," OWS [ challenge ] )
 
 <a href="#uri" class="smpl">absolute-URI</a> = &lt;absolute-URI, see <a href="#RFC3986" id="rfc.xref.RFC3986.26"><cite title="Uniform Resource Identifier (URI): Generic Syntax">[RFC3986]</cite></a>, <a href="https://tools.ietf.org/html/rfc3986#section-4.3">Section 4.3</a>&gt;
 <a href="#uri" class="smpl">absolute-path</a> = 1*( "/" segment )
 <a href="#header.accept" class="smpl">accept-ext</a> = OWS ";" OWS token [ "=" ( token / quoted-string ) ]
 <a href="#header.accept" class="smpl">accept-params</a> = weight *accept-ext
-<a href="#header.accept-ranges" class="smpl">acceptable-ranges</a> = ( *( "," OWS ) range-unit *( OWS "," [ OWS
- range-unit ] ) ) / "none"
+<a href="#header.accept-ranges" class="smpl">acceptable-ranges</a> = ( [ range-unit ] *( OWS "," OWS [ range-unit ] )
+ ) / "none"
 <a href="#obsolete.date.formats" class="smpl">asctime-date</a> = day-name SP date3 SP time-of-day SP year
 <a href="#challenge.and.response" class="smpl">auth-param</a> = token BWS "=" BWS ( token / quoted-string )
 <a href="#challenge.and.response" class="smpl">auth-scheme</a> = token
@@ -9513,15 +9510,15 @@ <h2 id="rfc.section.A" class="np"><a href="#rfc.section.A">Appendix A.</a>&nbsp;
 <a href="#rule.ranges-specifier" class="smpl">byte-ranges-specifier</a> = bytes-unit "=" byte-range-set
 <a href="#byte.ranges" class="smpl">bytes-unit</a> = "bytes"
 
-<a href="#challenge.and.response" class="smpl">challenge</a> = auth-scheme [ 1*SP ( token68 / [ ( "," / auth-param ) *(
- OWS "," [ OWS auth-param ] ) ] ) ]
+<a href="#challenge.and.response" class="smpl">challenge</a> = auth-scheme [ 1*SP ( token68 / ( [ auth-param ] *( OWS
+ "," OWS [ auth-param ] ) ) ) ]
 <a href="#charset" class="smpl">charset</a> = token
 <a href="#header.accept-encoding" class="smpl">codings</a> = content-coding / "identity" / "*"
 <a href="#rule.comment" class="smpl">comment</a> = "(" *( ctext / quoted-pair / comment ) ")"
 <a href="#header.content-range" class="smpl">complete-length</a> = 1*DIGIT
 <a href="#content.codings" class="smpl">content-coding</a> = token
-<a href="#challenge.and.response" class="smpl">credentials</a> = auth-scheme [ 1*SP ( token68 / [ ( "," / auth-param )
- *( OWS "," [ OWS auth-param ] ) ] ) ]
+<a href="#challenge.and.response" class="smpl">credentials</a> = auth-scheme [ 1*SP ( token68 / ( [ auth-param ] *( OWS
+ "," OWS [ auth-param ] ) ) ) ]
 <a href="#rule.comment" class="smpl">ctext</a> = HTAB / SP / %x21-27 ; '!'-'''
  / %x2A-5B ; '*'-'['
  / %x5D-7E ; ']'-'~'
@@ -9864,6 +9861,8 @@ <h3 id="rfc.section.I.6"><a href="#rfc.section.I.6">I.6.</a>&nbsp;<a href="#chan
                   </li>
                   <li>In <a href="#header.content-type" id="rfc.xref.header.content-type.5" title="Content-Type">Section&nbsp;6.2.1</a>, reference MIME Sniffing (&lt;<a href="https://github.com/httpwg/http-core/issues/51">https://github.com/httpwg/http-core/issues/51</a>&gt;)
                   </li>
+                  <li>In <a href="#abnf.extension" title="ABNF List Extension: #rule">Section&nbsp;11</a>, simplify the #rule mapping for recipients (&lt;<a href="https://github.com/httpwg/http-core/issues/164">https://github.com/httpwg/http-core/issues/164</a>&gt;, &lt;<a href="https://www.rfc-editor.org/errata/eid5257">https://www.rfc-editor.org/errata/eid5257</a>&gt;)
+                  </li>
                   <li>In <a href="#OPTIONS" id="rfc.xref.OPTIONS.4" title="OPTIONS">Section&nbsp;7.3.7</a>, remove misleading text about "extension" of HTTP is needed to define method payloads
                      (&lt;<a href="https://github.com/httpwg/http-core/issues/204">https://github.com/httpwg/http-core/issues/204</a>&gt;)
                   </li>
diff --git a/draft-ietf-httpbis-semantics-latest.xml b/draft-ietf-httpbis-semantics-latest.xml
index 26eef13fd..de71f1f50 100644
--- a/draft-ietf-httpbis-semantics-latest.xml
+++ b/draft-ietf-httpbis-semantics-latest.xml
@@ -9498,19 +9498,22 @@ Content-Encoding: gzip
   &lt;n&gt;#&lt;m&gt;element =&gt; element &lt;n-1&gt;*&lt;m-1&gt;( OWS "," OWS element )
 </artwork>
 <t>
-   For compatibility with legacy list rules, a recipient &MUST; parse and ignore
+   Empty elements do not contribute to the count of elements present.
+   A recipient &MUST; parse and ignore
    a reasonable number of empty list elements: enough to handle common mistakes
    by senders that merge values, but not so much that they could be used as a
    denial-of-service mechanism. In other words, a recipient &MUST; accept lists
    that satisfy the following syntax:
 </t>
 <artwork type="example">
-  #element =&gt; [ ( "," / element ) *( OWS "," [ OWS element ] ) ]
-  
-  1#element =&gt; *( "," OWS ) element *( OWS "," [ OWS element ] )
+  #element =&gt; [ element ] *( OWS "," OWS [ element ] )
 </artwork>
 <t>
-   Empty elements do not contribute to the count of elements present.
+   Note that because of the potential presence of empty list elements, the
+   RFC 5234 ABNF cannot enforce the cardinality of list elements, and
+   consequently all cases are mapped is if there was no cardinality specified.
+</t>
+<t>
    For example, given these ABNF productions: 
 </t>
 <artwork type="example">
@@ -11197,17 +11200,16 @@ Content-Encoding: gzip
 <x:ref>Accept-Language</x:ref> = *( "," OWS ) ( language-range [ weight ] ) *( OWS
  "," [ OWS ( language-range [ weight ] ) ] )
 <x:ref>Accept-Ranges</x:ref> = acceptable-ranges
-<x:ref>Allow</x:ref> = [ ( "," / method ) *( OWS "," [ OWS method ] ) ]
-<x:ref>Authentication-Info</x:ref> = [ ( "," / auth-param ) *( OWS "," [ OWS
- auth-param ] ) ]
+<x:ref>Allow</x:ref> = [ method ] *( OWS "," OWS [ method ] )
+<x:ref>Authentication-Info</x:ref> = [ auth-param ] *( OWS "," OWS [ auth-param ] )
 <x:ref>Authorization</x:ref> = credentials
 
 <x:ref>BWS</x:ref> = OWS
 
-<x:ref>Content-Encoding</x:ref> = *( "," OWS ) content-coding *( OWS "," [ OWS
- content-coding ] )
-<x:ref>Content-Language</x:ref> = *( "," OWS ) language-tag *( OWS "," [ OWS
- language-tag ] )
+<x:ref>Content-Encoding</x:ref> = [ content-coding ] *( OWS "," OWS [ content-coding
+ ] )
+<x:ref>Content-Language</x:ref> = [ language-tag ] *( OWS "," OWS [ language-tag ]
+ )
 <x:ref>Content-Length</x:ref> = 1*DIGIT
 <x:ref>Content-Location</x:ref> = absolute-URI / partial-URI
 <x:ref>Content-Range</x:ref> = byte-content-range / other-content-range
@@ -11226,11 +11228,10 @@ Content-Encoding: gzip
 <x:ref>Host</x:ref> = uri-host [ ":" port ]
 
 <x:ref>IMF-fixdate</x:ref> = day-name "," SP date1 SP time-of-day SP GMT
-<x:ref>If-Match</x:ref> = "*" / ( *( "," OWS ) entity-tag *( OWS "," [ OWS
- entity-tag ] ) )
+<x:ref>If-Match</x:ref> = "*" / ( [ entity-tag ] *( OWS "," OWS [ entity-tag ] ) )
 <x:ref>If-Modified-Since</x:ref> = HTTP-date
-<x:ref>If-None-Match</x:ref> = "*" / ( *( "," OWS ) entity-tag *( OWS "," [ OWS
- entity-tag ] ) )
+<x:ref>If-None-Match</x:ref> = "*" / ( [ entity-tag ] *( OWS "," OWS [ entity-tag ]
+ ) )
 <x:ref>If-Range</x:ref> = entity-tag / HTTP-date
 <x:ref>If-Unmodified-Since</x:ref> = HTTP-date
 
@@ -11241,10 +11242,9 @@ Content-Encoding: gzip
 
 <x:ref>OWS</x:ref> = *( SP / HTAB )
 
-<x:ref>Proxy-Authenticate</x:ref> = *( "," OWS ) challenge *( OWS "," [ OWS
- challenge ] )
-<x:ref>Proxy-Authentication-Info</x:ref> = [ ( "," / auth-param ) *( OWS "," [ OWS
- auth-param ] ) ]
+<x:ref>Proxy-Authenticate</x:ref> = [ challenge ] *( OWS "," OWS [ challenge ] )
+<x:ref>Proxy-Authentication-Info</x:ref> = [ auth-param ] *( OWS "," OWS [
+ auth-param ] )
 <x:ref>Proxy-Authorization</x:ref> = credentials
 
 <x:ref>RWS</x:ref> = 1*( SP / HTAB )
@@ -11254,26 +11254,24 @@ Content-Encoding: gzip
 
 <x:ref>Server</x:ref> = product *( RWS ( product / comment ) )
 
-<x:ref>Trailer</x:ref> = *( "," OWS ) field-name *( OWS "," [ OWS field-name ] )
+<x:ref>Trailer</x:ref> = [ field-name ] *( OWS "," OWS [ field-name ] )
 
 <x:ref>URI-reference</x:ref> = &lt;URI-reference, see <xref target="RFC3986" x:fmt="," x:sec="4.1"/>&gt;
 <x:ref>User-Agent</x:ref> = product *( RWS ( product / comment ) )
 
-<x:ref>Vary</x:ref> = "*" / ( *( "," OWS ) field-name *( OWS "," [ OWS field-name ]
- ) )
+<x:ref>Vary</x:ref> = "*" / ( [ field-name ] *( OWS "," OWS [ field-name ] ) )
 <x:ref>Via</x:ref> = *( "," OWS ) ( received-protocol RWS received-by [ RWS comment
  ] ) *( OWS "," [ OWS ( received-protocol RWS received-by [ RWS
  comment ] ) ] )
 
-<x:ref>WWW-Authenticate</x:ref> = *( "," OWS ) challenge *( OWS "," [ OWS challenge
- ] )
+<x:ref>WWW-Authenticate</x:ref> = [ challenge ] *( OWS "," OWS [ challenge ] )
 
 <x:ref>absolute-URI</x:ref> = &lt;absolute-URI, see <xref target="RFC3986" x:fmt="," x:sec="4.3"/>&gt;
 <x:ref>absolute-path</x:ref> = 1*( "/" segment )
 <x:ref>accept-ext</x:ref> = OWS ";" OWS token [ "=" ( token / quoted-string ) ]
 <x:ref>accept-params</x:ref> = weight *accept-ext
-<x:ref>acceptable-ranges</x:ref> = ( *( "," OWS ) range-unit *( OWS "," [ OWS
- range-unit ] ) ) / "none"
+<x:ref>acceptable-ranges</x:ref> = ( [ range-unit ] *( OWS "," OWS [ range-unit ] )
+ ) / "none"
 <x:ref>asctime-date</x:ref> = day-name SP date3 SP time-of-day SP year
 <x:ref>auth-param</x:ref> = token BWS "=" BWS ( token / quoted-string )
 <x:ref>auth-scheme</x:ref> = token
@@ -11290,15 +11288,15 @@ Content-Encoding: gzip
 <x:ref>byte-ranges-specifier</x:ref> = bytes-unit "=" byte-range-set
 <x:ref>bytes-unit</x:ref> = "bytes"
 
-<x:ref>challenge</x:ref> = auth-scheme [ 1*SP ( token68 / [ ( "," / auth-param ) *(
- OWS "," [ OWS auth-param ] ) ] ) ]
+<x:ref>challenge</x:ref> = auth-scheme [ 1*SP ( token68 / ( [ auth-param ] *( OWS
+ "," OWS [ auth-param ] ) ) ) ]
 <x:ref>charset</x:ref> = token
 <x:ref>codings</x:ref> = content-coding / "identity" / "*"
 <x:ref>comment</x:ref> = "(" *( ctext / quoted-pair / comment ) ")"
 <x:ref>complete-length</x:ref> = 1*DIGIT
 <x:ref>content-coding</x:ref> = token
-<x:ref>credentials</x:ref> = auth-scheme [ 1*SP ( token68 / [ ( "," / auth-param )
- *( OWS "," [ OWS auth-param ] ) ] ) ]
+<x:ref>credentials</x:ref> = auth-scheme [ 1*SP ( token68 / ( [ auth-param ] *( OWS
+ "," OWS [ auth-param ] ) ) ) ]
 <x:ref>ctext</x:ref> = HTAB / SP / %x21-27 ; '!'-'''
  / %x2A-5B ; '*'-'['
  / %x5D-7E ; ']'-'~'
@@ -11579,6 +11577,7 @@ Content-Encoding: gzip
 <ul>
   <li>Move <xref target="parameter"/> into its own section (<eref target="https://github.com/httpwg/http-core/issues/45"/>)</li>
   <li>In <xref target="header.content-type"/>, reference MIME Sniffing (<eref target="https://github.com/httpwg/http-core/issues/51"/>)</li>
+  <li>In <xref target="abnf.extension"/>, simplify the #rule mapping for recipients (<eref target="https://github.com/httpwg/http-core/issues/164"/>, <eref target="https://www.rfc-editor.org/errata/eid5257"/>)</li>
   <li>In <xref target="OPTIONS"/>, remove misleading text about "extension" of HTTP is needed to define method payloads (<eref target="https://github.com/httpwg/http-core/issues/204"/>)</li>
 </ul>
 </section>
diff --git a/httpbis.abnf b/httpbis.abnf
index 667ea1975..f35700ffb 100644
--- a/httpbis.abnf
+++ b/httpbis.abnf
@@ -8,14 +8,14 @@ Accept-Encoding = [ ( "," / ( codings [ weight ] ) ) *( OWS "," [ OWS ( codings
 Accept-Language = *( "," OWS ) ( language-range [ weight ] ) *( OWS "," [ OWS ( language-range [ weight ] ) ] )
 Accept-Ranges = acceptable-ranges
 Age = delta-seconds
-Allow = [ ( "," / method ) *( OWS "," [ OWS method ] ) ]
-Authentication-Info = [ ( "," / auth-param ) *( OWS "," [ OWS auth-param ] ) ]
+Allow = [ method ] *( OWS "," OWS [ method ] )
+Authentication-Info = [ auth-param ] *( OWS "," OWS [ auth-param ] )
 Authorization = credentials
 BWS = OWS
-Cache-Control = *( "," OWS ) cache-directive *( OWS "," [ OWS cache-directive ] )
-Connection = *( "," OWS ) connection-option *( OWS "," [ OWS connection-option ] )
-Content-Encoding = *( "," OWS ) content-coding *( OWS "," [ OWS content-coding ] )
-Content-Language = *( "," OWS ) language-tag *( OWS "," [ OWS language-tag ] )
+Cache-Control = [ cache-directive ] *( OWS "," OWS [ cache-directive ] )
+Connection = [ connection-option ] *( OWS "," OWS [ connection-option ] )
+Content-Encoding = [ content-coding ] *( OWS "," OWS [ content-coding ] )
+Content-Language = [ language-tag ] *( OWS "," OWS [ language-tag ] )
 Content-Length = 1*DIGIT
 Content-Location = absolute-URI / partial-URI
 Content-Range = byte-content-range / other-content-range
@@ -34,38 +34,38 @@ HTTP-name = %x48.54.54.50 ; HTTP
 HTTP-version = HTTP-name "/" DIGIT "." DIGIT
 Host = uri-host [ ":" port ]
 IMF-fixdate = day-name "," SP date1 SP time-of-day SP GMT
-If-Match = "*" / ( *( "," OWS ) entity-tag *( OWS "," [ OWS entity-tag ] ) )
+If-Match = "*" / ( [ entity-tag ] *( OWS "," OWS [ entity-tag ] ) )
 If-Modified-Since = HTTP-date
-If-None-Match = "*" / ( *( "," OWS ) entity-tag *( OWS "," [ OWS entity-tag ] ) )
+If-None-Match = "*" / ( [ entity-tag ] *( OWS "," OWS [ entity-tag ] ) )
 If-Range = entity-tag / HTTP-date
 If-Unmodified-Since = HTTP-date
 Last-Modified = HTTP-date
 Location = URI-reference
 Max-Forwards = 1*DIGIT
 OWS = *( SP / HTAB )
-Proxy-Authenticate = *( "," OWS ) challenge *( OWS "," [ OWS challenge ] )
-Proxy-Authentication-Info = [ ( "," / auth-param ) *( OWS "," [ OWS auth-param ] ) ]
+Proxy-Authenticate = [ challenge ] *( OWS "," OWS [ challenge ] )
+Proxy-Authentication-Info = [ auth-param ] *( OWS "," OWS [ auth-param ] )
 Proxy-Authorization = credentials
 RWS = 1*( SP / HTAB )
 Range = byte-ranges-specifier / other-ranges-specifier
 Referer = absolute-URI / partial-URI
 Retry-After = HTTP-date / delay-seconds
 Server = product *( RWS ( product / comment ) )
-TE = [ ( "," / t-codings ) *( OWS "," [ OWS t-codings ] ) ]
-Trailer = *( "," OWS ) field-name *( OWS "," [ OWS field-name ] )
-Transfer-Encoding = *( "," OWS ) transfer-coding *( OWS "," [ OWS transfer-coding ] )
+TE = [ t-codings ] *( OWS "," OWS [ t-codings ] )
+Trailer = [ field-name ] *( OWS "," OWS [ field-name ] )
+Transfer-Encoding = [ transfer-coding ] *( OWS "," OWS [ transfer-coding ] )
 URI-reference = <URI-reference, see [RFC3986], Section 4.1>
-Upgrade = *( "," OWS ) protocol *( OWS "," [ OWS protocol ] )
+Upgrade = [ protocol ] *( OWS "," OWS [ protocol ] )
 User-Agent = product *( RWS ( product / comment ) )
-Vary = "*" / ( *( "," OWS ) field-name *( OWS "," [ OWS field-name ] ) )
+Vary = "*" / ( [ field-name ] *( OWS "," OWS [ field-name ] ) )
 Via = *( "," OWS ) ( received-protocol RWS received-by [ RWS comment ] ) *( OWS "," [ OWS ( received-protocol RWS received-by [ RWS comment ] ) ] )
-WWW-Authenticate = *( "," OWS ) challenge *( OWS "," [ OWS challenge ] )
+WWW-Authenticate = [ challenge ] *( OWS "," OWS [ challenge ] )
 absolute-URI = <absolute-URI, see [RFC3986], Section 4.3>
 absolute-form = absolute-URI
 absolute-path = 1*( "/" segment )
 accept-ext = OWS ";" OWS token [ "=" ( token / quoted-string ) ]
 accept-params = weight *accept-ext
-acceptable-ranges = ( *( "," OWS ) range-unit *( OWS "," [ OWS range-unit ] ) ) / "none"
+acceptable-ranges = ( [ range-unit ] *( OWS "," OWS [ range-unit ] ) ) / "none"
 asctime-date = day-name SP date3 SP time-of-day SP year
 asterisk-form = "*"
 auth-param = token BWS "=" BWS ( token / quoted-string )
@@ -80,7 +80,7 @@ byte-range-spec = first-byte-pos "-" [ last-byte-pos ]
 byte-ranges-specifier = bytes-unit "=" byte-range-set
 bytes-unit = "bytes"
 cache-directive = token [ "=" ( token / quoted-string ) ]
-challenge = auth-scheme [ 1*SP ( token68 / [ ( "," / auth-param ) *( OWS "," [ OWS auth-param ] ) ] ) ]
+challenge = auth-scheme [ 1*SP ( token68 / ( [ auth-param ] *( OWS "," OWS [ auth-param ] ) ) ) ]
 charset = token
 chunk = chunk-size [ chunk-ext ] CRLF chunk-data CRLF
 chunk-data = 1*OCTET
@@ -94,7 +94,7 @@ comment = "(" *( ctext / quoted-pair / comment ) ")"
 complete-length = 1*DIGIT
 connection-option = token
 content-coding = token
-credentials = auth-scheme [ 1*SP ( token68 / [ ( "," / auth-param ) *( OWS "," [ OWS auth-param ] ) ] ) ]
+credentials = auth-scheme [ 1*SP ( token68 / ( [ auth-param ] *( OWS "," OWS [ auth-param ] ) ) ) ]
 ctext = HTAB / SP / %x21-27 ; '!'-'''
  / %x2A-5B ; '*'-'['
  / %x5D-7E ; ']'-'~'
diff --git a/lib/common-abnf.sh b/lib/common-abnf.sh
index d53be20ec..b72da5855 100755
--- a/lib/common-abnf.sh
+++ b/lib/common-abnf.sh
@@ -12,7 +12,7 @@ echo ""
 
 for i in "$@"
 do
-  $bap/bap -i $bap/core.abnf  -X rfc7405 -n "$i" 
+  $bap/bap -i $bap/core.abnf -L 1 -X rfc7405 -n "$i" 
 done | \
 	fgrep -v ", defined in [Part" | \
 	fgrep -v ", defined in [Messaging" | \