Recognize rdf:dirLangString

spec/index.html

@@ -774,8 +774,9 @@ <h2>Literals and datatypes</h2>
     for that datatype.</p>
 
   <p>RDF processors are not required to <a>recognize</a> any datatype IRIs other than
-    <a data-cite="RDF12-CONCEPTS#dfn-language-tagged-string"><code>rdf:langString</code></a>
-    and <a data-cite="XMLSCHEMA11-2#string"><code>xsd:string</code></a>,
+    <a data-cite="XMLSCHEMA11-2#string"><code>xsd:string</code></a>,
+    <a data-cite="RDF12-CONCEPTS#dfn-language-tagged-string"><code>rdf:langString</code></a>, and
+    <a data-cite="RDF12-CONCEPTS#dfn-dir-lang-string"><code>rdf:dirLangString</code></a>
     but when IRIs listed in 
     <a data-cite="RDF12-CONCEPTS#section-Datatypes">Section 5</a> of [[!RDF12-CONCEPTS]]
     are <a>recognized</a>, they MUST be interpreted as described there, and when the IRI <code>rdf:PlainLiteral</code> is <a>recognized</a>, it MUST be interpreted to denote the datatype defined in [[!RDF-PLAIN-LITERAL]]. RDF processors MAY recognize other datatype IRIs, but when other datatype IRIs are <a>recognized</a>, the mapping between the datatype IRI and the datatype it <a>denotes</a> MUST be specified unambiguously, and MUST be fixed during all RDF transformations or manipulations. In practice, this can be achieved by the IRI linking to an external specification of the datatype which describes both the components of the datatype itself and the fact that the IRI identifies the datatype, thereby fixing a value of the <a>datatype map</a> of this IRI.</p>