title: JavaFX purpose of xmlns:fx
body: <p><a href="https://docs.oracle.com/javafx/2/get_started/fxml_tutorial.htm" rel="noreferrer">This Java tutorial by Oracle</a> says that</p>
  
  <blockquote>
    <p>The xmlns:fx attribute is always required and specifies the fx namespace.</p>
  </blockquote>
  
  <p>but what exactly is the fx namespace? <br>
  And what values qualify for this attribute?</p>