Add grammar pieces for framing.

Relates to w3c/json-ld-framing#28.

Author: gkellogg

index.html

@@ -10535,6 +10535,26 @@ <h2>Node Objects</h2>
     </ul>
   </section>
 
+  <section class="normative"><h2>Frame Objects</h2>
+    <p>When <a>framing</a>, a <a>frame object</a> extends a <a>node object</a> to allow
+      members used specifically for <a>framing</a>.</p>
+    <ul>
+      <li>A <a>frame object</a> MAY include a <a>default object</a> as the value of any key
+        which is not a <a>keyword</a>.
+        Values of <code>@default</code> MAY include the value <code>@null</code>,
+        or an <a>array</a> containing only <code>@null</code>, in addition to other values
+        allowed in the grammar for values of <a>member</a> keys expanding to <a>absolute IRIs</a>.</li>
+      <li>The values of <code>@id</code> and <code>@type</code> MAY additionally be an empty <a>dictionary</a>,
+        an <a>array</a> containing only  an empty <a>dictionary</a>,
+        an <a>array</a> of <a>IRIs</a>.</li>
+      <li>A <a>frame object</a> MAY include a <a>member</a> with the key <code>@embed</code> with
+        any value from <code>@always</code>, <code>@list</code>, and <code>@never</code>.</li>
+      <li>A <a>frame object</a> MAY include <a>members</a> with the boolean valued
+        keys <code>@explicit</code>, <code>@omitDefault</code>, or <code>@requireAll</code></li>
+    </ul>
+    <p>See [[JSON-LD11-FRAMING]] for a description of how <a>frame objects</a> are used.</p>
+  </section>
+
   <section class="normative">
     <h2>Graph Objects</h2>