Update spec/index.html

Co-authored-by: Olaf Hartig <[email protected]>

Author: afs

spec/index.html

@@ -5838,9 +5838,9 @@ <h5>SameValue</h5>
                 of the datatype.
               </p>
               <p>
-                The function `sameValue` returns true or false in cases where
-                the SPARQL processor can determine that the values of the
-                arguments are equal or are not equal. If the SPARQL processor
+                If the two arguments are literals, the function `sameValue` returns `true` or `false` in cases where
+                the SPARQL processor can determine that the values of these
+                literals are equal or are not equal. If the SPARQL processor
                 can not be sure, it returns `error`.
               </p>
             </div>