--- a/spec/latest/json-ld-syntax/index.html	Mon Nov 07 13:27:25 2011 +0800
+++ b/spec/latest/json-ld-syntax/index.html	Mon Nov 07 13:40:52 2011 +0800
@@ -587,7 +587,7 @@
 <code>http://xmlns.com/foaf/0.1/name</code>. This allows JSON-LD documents to
 be constructed using the common JSON practice of simple name/value pairs while
 ensuring that the data is useful outside of the page, API or database in which it
-resides.
+resides. The value of a term mapping MUST be a simple string with the lexical form of an absolute <tref>IRI</tref>.
 </p>
 
 <p>These Linked Data <tref>term</tref>s are typically collected in a context document that would look something like this:</p>
@@ -1356,7 +1356,8 @@
   a way to set a base IRI to be used for all properties and types that aren't based on terms,
   prefixes or absolute IRIs. Much like the <code>@base</code> keyword, the <code>@vocab</code> keyword
   can be used to set a base <tref>IRI</tref> to use for all types and properties that don't otherwise resolve to
-  an absolute <tref>IRI</tref>.
+  an absolute <tref>IRI</tref>. The <code>@vocab</code> mapping MUST have a value of a simple string with the
+  lexical form of an absolute IRI.</p>
 
 <pre class="example" data-transform="updateExample">
 <!--