adds note for issue #308

Author: hartig

spec/index.html

@@ -10663,6 +10663,8 @@ <h3>Evaluation Semantics</h3>
             <li>|L| : a solution sequence</li>
             <li>|F| : an <a href="#expressions">expression</a></li>
           </ul>
+<div class="issue" data-number="308">
+  |L| should not be a solution sequence but an <a href="#defn_AlgebraicQueryExpression">algebraic query expression</a>.</div>
 <div class="issue" data-number="225">
   The definitions in this section do not cover the cases in which
   |A| is a sequence or a multiset of solution mappings.</div>