title: ATL Metamodel contains several classifiers with same name error
body: <p>I have a small ATL program converting BPMN2.0 to another model as:</p>
  
  <pre><code>-- @nsURI MM1=http://www.my.site/path/to/my/MM1
  -- @nsURI BPMN20=http://www.omg.org/spec/BPMN/20100524/MODEL-XMI
  -- @path reo=/BPMN20reo/reo.ecore
  rule definition2module {
      from
          b: BPMN20!Definitions
      to
          m: reo!Connector(name&lt;-b.name)
  }
  </code></pre>
  
  <p>module test;
  create OUT: reo from IN: BPMN20;</p>
  
  <p>The code generates the following errors. I believe it has something to do with loading/finding BPMN 2 model. I tried also using the BPMN 2 file address but still I get the following errors:</p>
  
  <p>Metamodel contains several classifiers with same name: DocumentRoot
  Metamodel contains several classifiers with same name: DocumentRoot
  Metamodel contains several classifiers with same name: di::DocumentRoot
  Metamodel contains several classifiers with same name: DocumentRoot</p>
  
  <p>Here is my code <a href="https://github.com/behnaaz/BPMN2ATL" rel="nofollow">https://github.com/behnaaz/BPMN2ATL</a></p>