Associations between classes

Hi I'm looking for a way to define some kind of associations between classes. Let me explain by an example what I mean exactly: I want to collect structured data for countries and its regions. To achieve this I define to classes, CountryClass and a RegionClass (incl. the sheets and templates). Now the user should be able to create new country objects _and_ he should have the possibility (in the form itself) to define which regions belong to a country. I tried to achieve this by adding a database list property to the country class with an appropriate hibernate query which selects all region documents. This let the user select one or more regions for a country. This is fine so far but - Is there any more general or a better way to achieve this associations (e.g. without hibernate queries)? - How can I adapt my ClassSheet so that the selected region associations are hyperlinked to the appropriate region objects? Thanks Yves