title: Compatibility and migration from Java 9 to Java 8
body: <p>I'm reading the <a href="http://openjdk.java.net/projects/jigsaw/spec/sotms/" rel="noreferrer">document</a> about the new Java 9 module system.</p>
  
  <p>The paragraph <strong>3 Compatibility &amp; migration</strong> explains how to migrate code
  from Java 8 to Java 9, but says nothing on how "migrate" or run an application
  written in Java 9 to pre Java 9 runtimes.</p>
  
  <p>So, if I have, say a JAR application written in a <em>modularity way</em> (every module has a module descriptor) what does happen if I deploy it on, i.e, a JDK 8 runtime?</p>