Subset selection of EA.Elements in a Template Fragment for Document Generation?

[Daiim]

I define a model document with a custom template.
The document generator iterates over all elements of one or more package elements that I've assigned to the model document as attributes.

For each element in this package, I'd like to aggregate a set of elements from the model using a template fragment and a custom script (or SQL query).

My question now is: What does the SQL query or custom script need to return so that the Document Generator iterates over this result set and I can use the fields Element.Notes, Element.Name, etc.? I've tried EAGUID, ElementGUID, etc. - that doesn't seem to be sufficient.

Current Idea:
Model Document for Package A --> Document Generator iterates over all Elements of Package A --> Script Template is called for each Element E1..n --> Script Template selects Elementset ES1 for Element E1 .. ESn for Element En --> Script Template uses <Element.Name> for each Element inside the Elementset (..?)

What am I missing?

Thanks for your help and any hint or tip.

Daiim