Filtering users

It is not fully clear to me how I can filter readers (clients) in term of which mine cards they can look at, senging EMM etc.
On particular it is not fully clear if and how I could use GROUP, CAID, IDENT, AU and/or any other parameters I am missing here.

Supposing I have 1 local card (i.e. A) and two remote cards (i.e. B and C) how can I address USER 1 to card A only, user 2 to card sA and B, user 3 to cards A, B and C ?

thanks in advance

Uh ?!? This is what I did and I thought it was wrong since my readers cannot see my cards, despite they are all "connected"
What is the purpose of CAID and IDENT field in the account section then ?

will keep on studying ;)
Thx anyway