diff --git a/spec/index.html b/spec/index.html
index 272e758..faf5844 100644
--- a/spec/index.html
+++ b/spec/index.html
@@ -7926,7 +7926,6 @@ <h5>TZ</h5>
           </section>
         </section>
 
-        <!-- QT -->
         <section id="func-triple-terms">
           <h4>Functions on Triple Terms</h4>
           <section id="func-triple">
@@ -7956,17 +7955,26 @@ <h5>TRIPLE</h5>
               the function returns a triple term with these three elements.
               Otherwise, the function raises an error.
             </p>
-
             <p>
               As a shorthand notation, the <code>TRIPLE</code> function 
               can also be written in the form of a
               <a href="#rExprTripleTerm">triple term expression</a>
-              using <code>&lt;&lt;(</code> and <code>)&gt;&gt;</code>.  There is a
-              syntax limitation to this shorthand form: the three elements of
-              the triple term expression can only be variables and directly
-              written RDF terms, not arbitrary expressions. 
-              In contrast, the function form, <code>TRIPLE</code>,
-              can be used with arbitrary expressions.
+              using <code>&lt;&lt;(</code> and <code>)&gt;&gt;</code>.  There are
+              syntax limitations to this shorthand form:
+            </p>
+            <ul>
+              <li>each of the three elements of the triple term expression can only be
+                a <a href="#defn_QueryVariable">variable</a>
+                or a directly written [=RDF term=], not an arbitrary expression.
+              </li>
+              <li>
+                the syntax of the subject and predicate positions is limited to an
+                <a data-cite="RDF12-CONCEPTS#dfn-iri">IRI</a> or a
+                <a href="#defn_QueryVariable">variable</a>.
+              </li>
+            </ul>
+            <p>
+              The function form, <code>TRIPLE</code>, can be used with arbitrary expressions.
             </p>
             <pre class="query nohighlight">
               VERSION "1.2"
@@ -8051,7 +8059,6 @@ <h5>isTRIPLE</h5>
             </p>
           </section>
         </section>
-        <!-- QT -->
 
         <section id="func-hash">
           <h4>Hash Functions</h4>
@@ -12109,7 +12116,7 @@ <h3>Grammar</h3>
                 <td><code>[123]&nbsp;&nbsp;</code></td>
                 <td><code><span class="doc-ref" id="rTripleTermDataSubject">TripleTermDataSubject</span></code></td>
                 <td>&nbsp;&nbsp;::=&nbsp;&nbsp;</td>
-                <td><code class="gRuleBody"><a href="#riri">iri</a> | <a href="#rRDFLiteral">RDFLiteral</a> | <a href="#rNumericLiteral">NumericLiteral</a> | <a href="#rBooleanLiteral">BooleanLiteral</a> | <a href="#rTripleTermData">TripleTermData</a></code></td>
+                <td><code class="gRuleBody"><a href="#riri">iri</a></code></td>
               </tr>
 
               <tr style="vertical-align: baseline">
@@ -12214,7 +12221,7 @@ <h3>Grammar</h3>
                 <td><code>[138]&nbsp;&nbsp;</code></td>
                 <td><code><span class="doc-ref" id="rExprTripleTermSubject">ExprTripleTermSubject</span></code></td>
                 <td>&nbsp;&nbsp;::=&nbsp;&nbsp;</td>
-                <td><code class="gRuleBody"><a href="#riri">iri</a> | <a href="#rRDFLiteral">RDFLiteral</a> | <a href="#rNumericLiteral">NumericLiteral</a> | <a href="#rBooleanLiteral">BooleanLiteral</a> | <a href="#rVar">Var</a> | <a href="#rExprTripleTerm">ExprTripleTerm</a></code></td>
+                <td><code class="gRuleBody"><a href="#riri">iri</a> | <a href="#rVar">Var</a></code></td>
               </tr>
 
               <tr style="vertical-align: baseline">
diff --git a/spec/sparql.bnf b/spec/sparql.bnf
index d24d335..8b085e9 100644
--- a/spec/sparql.bnf
+++ b/spec/sparql.bnf
@@ -120,7 +120,7 @@ TripleTerm                ::= '<<(' TripleTermSubject Verb TripleTermObject ')>>
 TripleTermSubject         ::= Var | iri | RDFLiteral | NumericLiteral | BooleanLiteral | BlankNode | TripleTerm
 TripleTermObject          ::= Var | iri | RDFLiteral | NumericLiteral | BooleanLiteral | BlankNode | TripleTerm
 TripleTermData            ::= '<<(' TripleTermDataSubject ( iri | 'a' ) TripleTermDataObject ')>>'
-TripleTermDataSubject     ::= iri | RDFLiteral | NumericLiteral | BooleanLiteral | TripleTermData
+TripleTermDataSubject     ::= iri
 TripleTermDataObject      ::= iri | RDFLiteral | NumericLiteral | BooleanLiteral | TripleTermData
 VarOrIri                  ::= Var | iri
 Var                       ::= VAR1 | VAR2
@@ -138,7 +138,7 @@ UnaryExpression           ::= '!' UnaryExpression
                           |   PrimaryExpression
 PrimaryExpression         ::= BrackettedExpression | BuiltInCall | iriOrFunction | RDFLiteral | NumericLiteral | BooleanLiteral | Var | ExprTripleTerm
 ExprTripleTerm            ::= '<<(' ExprTripleTermSubject Verb ExprTripleTermObject ')>>'
-ExprTripleTermSubject     ::= iri | RDFLiteral | NumericLiteral | BooleanLiteral | Var | ExprTripleTerm
+ExprTripleTermSubject     ::= iri | Var
 ExprTripleTermObject      ::= iri | RDFLiteral | NumericLiteral | BooleanLiteral | Var | ExprTripleTerm
 BrackettedExpression      ::= '(' Expression ')'
 BuiltInCall               ::= Aggregate