[formtypes] Clarify FORM_TYPE field type on 'submit' type forms

Since 'submit' type forms are allowed to omitt the explicit declartion
of the form field type, we must specify that the special FORM_TYPE
field in 'submit' forms may not carry a type declartion.

This just reflects what it is done in the wild anyways.

Co-authored-by: Marvin W <git@larma.de>

xep-0068.xml

@@ -23,6 +23,12 @@
   <registry/>
   &hildjj;
   &stpeter;
+  <revision>
+    <version>1.3.0</version>
+    <date>2020-05-05</date>
+    <initials>fs</initials>
+    <remark>Clarify field type handling of the FORM_TYPE field on submission forms.</remark>
+  </revision>
   <revision>
     <version>1.2</version>
     <date>2012-05-28</date>
@@ -115,7 +121,7 @@
 
 <section1 topic='Use Cases' anchor='usecases'>
     <section2 topic='Unspecified Form' anchor='usecases-unspecified'>
-      <p>These are forms that do not have a hidden field of name FORM_TYPE.
+      <p>These are forms with type=&quot;form&quot; or type=&quot;result&quot; that do not have a hidden field of name FORM_TYPE or forms with type=&quot;submit&quot; that do not have any field of name FORM_TYPE.
         Existing processing rules still apply.</p>
       <example caption='Message with no FORM_TYPE'><![CDATA[
 <message
@@ -171,7 +177,7 @@
     </section2>
     <section2 topic='Incorrectly Specified FORM_TYPE' anchor='usecases-incorrect'>
 
-    <p>If the FORM_TYPE field is not hidden, it MUST be ignored as a context indicator.</p>
+    <p>If the FORM_TYPE field is not hidden in a form with type=&quot;form&quot; or type=&quot;result&quot;, it MUST be ignored as a context indicator.</p>
 
       <example caption='Message with bad FORM_TYPE'><![CDATA[
 <message to="juliet@capulet.com" from="romeo@montague.net/garden">
@@ -192,7 +198,7 @@
 ]]></example>
   </section2>
   <section2 topic='IQ Example' anchor='usecases-IQ'>
-    <p>The following example shows a user's interaction with a Multi-User Chat room in order to register with the room.</p>
+    <p>The following example shows a user's interaction with a Multi-User Chat room in order to register with the room. Note that as per &xep0004; the form field "type" attribute may be omitted in data forms of type "submit".</p>
     <example caption='User Requests Registration Requirements'><![CDATA[
 <iq
     from='hag66@shakespeare.lit/pda'
@@ -294,7 +300,7 @@
 </section1>
 
 <section1 topic='Implementation Notes' anchor='impl'>
-    <p>If the FORM_TYPE field is not type=&quot;hidden&quot;, it does not have the special meaning defined herein.</p>
+    <p>If the FORM_TYPE field is not type=&quot;hidden&quot; in a data form with type &quot;form&quot; or type &quot;result&quot;, it does not have the special meaning defined herein. Data forms with the type "submit" are free to omit any explicit field type declaration (as per &xep0004; § 3.2), as the type is implied by the corresponding "form"-type data form. As consequence, implementations MUST treat a FORM_TYPE field without an explicit type attribute, in data forms of type "submit", as the FORM_TYPE field with the special meaning defined herein.</p>
     <p>If the form is used in an IQ, the namespace of the &lt;query/&gt; element SHOULD match the base namespace of the FORM_TYPE. (One possible way of solving this problem would have been to reuse the &lt;query/&gt; tag from the IQ form of jabber:x:data within messages, but that would have meant that existing clients would not have been able to participate in these exchanges.)</p>
 </section1>