XML error highlighting and schemas

I have a project that includes a working Maven project.xml file.

Idea shows the file as a sea of red. I searched the Maven user mailing list, and many online resources, but I was unable to find example code illustrating a project xml incorperating a schema.

So for Maven project.xml files, does anyone have an example that Idea's XML editor likes?

How about any other trivial/sample xml documents with schemas that Idea likes?