title: dojo.store.Observable, JSON REST and queryEngine
body: <p>Does anybody know how to use the JsonRest store in dojo witn an Observable weapper, like the one in dojo.store.Observable?</p>
  
  <p>What do I need, server side, to implement the store and make it work as an Observable one?  What about the client side? 
  The documentation says <a href="http://dojotoolkit.org/reference-guide/1.7/dojo/store/Observable.html" rel="noreferrer">http://dojotoolkit.org/reference-guide/1.7/dojo/store/Observable.html</a></p>
  
  <blockquote>
    <p>If you are using a server side store like the JsonRest store, you will need to provide a queryEngine in order for the update objects to be properly included or excluded from queries. If a queryEngine is not available, observe listener will be called with an undefined index.</p>
  </blockquote>
  
  <p>But, I have no idea what they mean. I have never created a store myself, and am not 100% familiar with queryEngine (to be honest, I find it a little confusing). Why is queryEngine needed? What does the doc mean by "undefined index"? And how do you write a queryEngine for a JsonRest store? Shouldn't I use some kind of web socket for an observable REST store, since other users might change the data as well?</p>
  
  <p>Confused!</p>