Update named graph example to use the W3C Prov Ontology

spec/latest/json-ld-syntax/index.html

@@ -2262,14 +2262,14 @@ <h2>Named Graphs</h2>
   <!--
   {
     "@context": {
-      "asOf": "http://purl.org/net/provenance/ns#accessedResource",
+      "generatedAt": "http://www.w3.org/ns/prov#generatedAtTime",
       "Person": "http://xmlns.com/foaf/0.1/Person",
       "name": "http://xmlns.com/foaf/0.1/name",
       "knows": "http://xmlns.com/foaf/0.1/knows",
       "xsd": "http://www.w3.org/2001/XMLSchema#"
     },
     ****"@id": "http://example.org/graphs/73",
-    "asOf": { "@value": "2012-04-09", "@type": "xsd:date" },
+    "generatedAt": { "@value": "2012-04-09", "@type": "xsd:date" },
     "@graph":****
     [
       {
@@ -2293,8 +2293,8 @@ <h2>Named Graphs</h2>
     that is identified by the <tref>IRI</tref>
     <code>http://example.org/graphs/73</code>. That graph is composed of the
     statements about Manu and Gregg. Metadata about the graph itself is also
-    expressed via the <code>asOf</code> property, which specifies when the
-    information was retrieved from the Web. An alternative view of the
+    expressed via the <code>generatedAt</code> property, which specifies when
+    the graph was generated. An alternative view of the
     information above is represented in table form below:</p>
 
   <table class="example">
@@ -2309,7 +2309,7 @@ <h2>Named Graphs</h2>
   <tr>
     <td>http://example.org/graphs/73</td>
     <td>http://example.org/graphs/73</td>
-    <td>http://purl.org/net/provenance/ns#accessedResource</td>
+    <td>http://www.w3.org/ns/prov#generatedAtTime</td>
     <td>2012-04-09</td>
     <td>http://www.w3.org/2001/XMLSchema#date</td>
   </tr>