Captcha: allow labels to be the empty string, for "UI should supply"captcha

1 files changed, 27 insertions, 3 deletions

diff --git a/spec/Channel_Interface_Captcha_Authentication.xml b/spec/Channel_Interface_Captcha_Authentication.xml
index 5cbfc236..22f3440f 100644
--- a/spec/Channel_Interface_Captcha_Authentication.xml
+++ b/spec/Channel_Interface_Captcha_Authentication.xml
@@ -92,9 +92,33 @@ Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.</
       </tp:member>
       <tp:member type="s" name="Label">
         <tp:docstring xmlns="http://www.w3.org/1999/xhtml">
-          <p>A human-readable label for the challenge, as defined in XEP-0158.
-            In particular, when Type = <code>qa</code>, this is a plain-text
-            question for the user to answer.</p>
+          <p>A human-readable label for the challenge, as defined in
+            XEP-0158.</p>
+
+          <p>If the server does not supply a label for a challenge of type
+            other than <code>qa</code>, connection managers SHOULD set Label
+            to an empty string instead of generating their own text.
+            If the Label is an empty string, the Handler SHOULD replace
+            it with a generic label in the user's locale, such as
+            the strings suggested in XEP-0158 (for instance,
+            <code>Enter the text you see</code> for <code>ocr</code>
+            challenges). The Handler MAY use those generic labels
+            in any case, as per
+            <a href="http://xmpp.org/extensions/xep-0158.html#i18n">the
+              Internationalization Considerations section of XEP-0158</a>.</p>
+
+          <tp:rationale>
+            <p>Connection managers are not usually localized, so text
+              generated by the connection manager would be in English,
+              regardless of the user's locale. The Handler is better-placed
+              to generate a generic Label in the user's locale.</p>
+          </tp:rationale>
+
+          <p>For challenges of type <code>qa</code>, the Label is a plain-text
+            question for the user to answer. The connection manager
+            SHOULD NOT provide an empty Label; if it does, the Handler
+            SHOULD treat that challenge as impossible, and SHOULD NOT
+            attempt to display it.</p>
         </tp:docstring>
       </tp:member>
       <tp:member type="u" name="Flags" tp:type="Captcha_Flags">