Troubles with polymorphics associations


Since some days, I try to create a dynamic user profiling system. In
this system, users can use many fields defined in a list.

In these fields, there are ones which admit a scalar value (like
firstname or birthday) and others which admit a collection (like
skills or visited countries) of value.

I have some troubles with that… How can i manage these polymorphic
fields ? Can you help me the define my models and their relations ?

Thanks for reading,