As <code>Context</code>
instances are not guaranteed to be thread-safe in general, all context
operations must be synchronized as needed.

<h4>Exception Handling</h4>

When a listener registers for events with a context, the context might
need to do some internal processing in order to collect information
required to generate the events.  The context, for example, might need
to make a request to the server to register interest in changes
on the server that will eventually be translated into events.
If an ex