Yes, this is another one that can be of your interest,

You can define Master - Detail relationship files recursively. Complicated?, let me give an example:

Lets imagine a teacher that has to track its students tasks. He gives his students so many tasks that he must group the tasks by student. At the same time he teachs to so many students, that he has to group them by classroom, this way he can search and locate any task of any student of any classroom much more easily.

So, we have a classroom file, where each record points to zero or many students of a students file, where at the same time, each record points to zero or many tasks of a tasks file. Just below an example made, where we allready inserted classrooms, students, and tasks.

Here we have the Classroom portlet with "Classroom 1A" selected,

As we have "Classroom 1A" selected, only students from that classroom are listed on the students portlet, were now we selected "Student 001 of 1A",

This way finally we access on the Tasks portlet, only to the tasks of previous selected student. Nice eh?

Here you have the XMLPorletFactory definition for the example above, just download and generate Liferay Crud portlet (MultiDetailFiles.xml)

Remember <detail> fields are available in 6.1.x and 6.0.x generations.

Liferay CRUD portlet development is getting easier every day.
Saludos, Jack.