Link two xml files

I have two xml files with different structures and need to link them.

XML 1:

<Departments>
  <Department Id='D1' />
</Departments>`

XML 2:

<Faculty Id='F1'&g开发者_开发知识库t;
  <Classrooms><Classroom Name='CR1' /><Classroom Name='CR2' /></Classrooms>
</Faculty>
<Faculty Id='F2'>
  <Classrooms><Classroom Name='CR3' /><Classroom Name='CR4' /></Classrooms>
</Faculty>

Now I want to link in a way that if I provide 'CR1' and 'D1' as my inputs, it should return F1. I want to link department (XML 1) and faculty (XML 2). What could be the best way to do it?

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If you have the possibility to change the XML structure I would add a link to the department through an attribute on faculty in XML2 (department="d1" for example).