title: How can I mix parent POMs in a Maven multi-module build?
body: <p>I have a Maven multi-module project and I need two different parent POMs in this build. The first one is the real parent POM for most modules in the project but one module is a demo project which uses the parent POM of a completely different project (because it's a demo how to use my project to generate code for the second project).</p>
  
  <p>The build works but I get a warning:</p>
  
  <pre><code>[WARNING] 
  [WARNING] Some problems were encountered while building the effective model for my_project:my_project.demo:jar:5.0.0-SNAPSHOT
  [WARNING] 'parent.relativePath' points at my_project:parent instead of other_project:parent, please verify your project structure @ line 5, column 10
  [WARNING] 
  [WARNING] It is highly recommended to fix these problems because they threaten the stability of your build.
  [WARNING] 
  [WARNING] For this reason, future Maven versions might no longer support building such malformed projects.
  [WARNING] 
  </code></pre>
  
  <p>Since <code>other_project</code> is not really a module of my build, it can be anywhere. This means I can't give a relative path.</p>
  
  <p>How can I fix this warning?</p>