@context takes a string expanding to an IRI, not just an IRI (from issue #135).
--- a/spec/latest/json-ld-syntax/index.html Sun Jun 24 18:25:13 2012 -0700
+++ b/spec/latest/json-ld-syntax/index.html Sun Jun 24 18:28:59 2012 -0700
@@ -2343,7 +2343,7 @@
<li>An <code>@id</code> keyword and a <code>@container</code> keyword MUST NOT exist in the same <tref>JSON object</tref>.</li>
<li>A <tref>subject definition</tref> MAY contain a <code>@context</code> property.</li>
<li>A <code>@context</code> value MUST NOT contain an embedded <code>@context</code> definition.</li>
-<li>The value associated with the <code>@context</code> keyword MUST be an <tref>IRI</tref>, a <tref>JSON object</tref>, null, or an <tref>array</tref> containing a combination of the allowed values.</li>
+<li>The value associated with the <code>@context</code> keyword MUST be a string expanding to an <tref>IRI</tref>, a <tref>JSON object</tref>, null, or an <tref>array</tref> containing a combination of the allowed values.</li>
<li>The value associated with the keys used in a <code>@context</code> MUST be a <code>null</code>, an <tref>IRI</tref>, or a <tref>JSON object</tref>.</li>
<li>For each value that is a <tref>JSON object</tref> that is associated with a key in a <code>@context</code>:
<ol>