--- a/spec/latest/json-ld-api/index.html	Mon Apr 09 12:45:42 2012 -0700
+++ b/spec/latest/json-ld-api/index.html	Mon Apr 09 13:19:33 2012 -0700
@@ -960,6 +960,9 @@
                   performing <a href="#iri-expansion">IRI Expansion</a> on the associated value. If the result of the IRI
                   mapping is an <tref>absolute IRI</tref>, merge the property into the <tref>local context</tref>
                   <tref>term mapping</tref>.</li>
+                <li>Otherwise, if the property's value is <code>null</code> remove mapping, coercion,
+                  container and language information associated with property from the
+                  <tref>local context</tref>.</li>
                 <li>Otherwise, the <em>property</em>'s <em>value</em> MUST be a <tref>JSON object</tref>.
                   <ol class="algorithm">
                     <li>If the <em>property</em> has the form of <tref>term</tref>, it's <em>value</em> MUST have an

--- a/spec/latest/json-ld-syntax/index.html	Mon Apr 09 12:45:42 2012 -0700
+++ b/spec/latest/json-ld-syntax/index.html	Mon Apr 09 13:19:33 2012 -0700
@@ -563,7 +563,7 @@
 <h3>The Context</h3>
 
 <p>In JSON-LD, a <tdef>context</tdef> is used to map <tref>term</tref>s, i.e., keys with associated values
-  in an JSON document, to <tref>IRI</tref>s. A <tdef>term</tdef> is a short word that MAY be expanded to an
+  in an JSON document, to <tref>IRI</tref>s. A <tdef>term</tdef> is a short word that expands to an
   <tref>IRI</tref>. A <tref>term</tref> MUST have the lexical form of <cite><a
   href="http://www.w3.org/TR/2009/REC-xml-names-20091208/#NT-NCName">NCName</a></cite>
   (see [[XML-NAMES]]).</p>
@@ -636,7 +636,7 @@
 for certain <tref>term</tref>s as well as other processing instructions for
 the JSON-LD processor.</p>
 
-<p>Contexts may be specified in-line. This ensures that JSON-LD documents
+<p>Contexts MAY be specified in-line. This ensures that JSON-LD documents
 can be processed when a JSON-LD processor does not have access to the Web.</p>
 
 <pre class="example" data-transform="updateExample">
@@ -671,6 +671,10 @@
   <tref>term</tref>s MUST be overridden using a last-defined-overrides
   mechanism.</p>
 
+<p class="note">If a <tref>term</tref> is re-defined within a context, all previous
+  rules associated with the previous definition is removed. A <tref>term</tref> defined
+  in a previous context MUST be removed, if it is defined to <code>null</code>.</p>
+
 <p>
   The set of contexts defined within a specific <tref>JSON Object</tref> are
   referred to as <tdef>local context</tdef>s. The