Hi Bert,
IMO what gives context is the OPT that constrains the underlying reference model, queries are based on archetypes and paths defined in OPTs and SNOMED expressions are just a way of creating semantically complex criteria for querying, nothing more.
That is why SNOMED alone can’t be used for querying.
I agree with that, else, you would not need OpenEhr at all 
Of course, if not so, it can easily flow over the capability of machines and networks, tuning is one of the most important subjects when querying very large repositories.
Bert
Hi Georg,
Please see comments inline
Hi Seref,
Thank you very much for your clarifications.
So, the SELECT in AQL works like a JOIN in SQL (or like the behavior of Xquery and Sparql with which I am not that much familar yet). This is something that should be better emphasized in the documentation. As you say that many people ask for a solution that creates concatenated facts in the same cell, I would assume that some people not only wish for this behavior but even assume it is indeed the actual behavior.
Greetings
Georg