Where is the getbtcaddressbalance json-rpc function?

[jquiroga]

If the client verifier of transactions is sound it must calculate that balance some where to see if the transaction is even possible.

Where is that very useful functionality reflected in the json-rpc calls?

We as users (web programmers) should be able to do a pre-verification before even trying sending with the real balance and not an 'account' balance.

Thanks.