question_about_erlang_and_cqrs.txt

Hi,
I watched your presentation about CQRS and Erlang at NDC Oslo. 
Before I ask you something, please now I never used Erlang so it could my 
lack of knowledge on the language that led me to ask you this question.
I have a question about the demo code:

`
attempt_command({withdraw_money, Amount}, State) ->
	NewBalance = State#state.balance - Amount,
	Id = State#state.id,

	Event = case(NewBalance < 0) of
		false ->
			#bank_account_money_withdrawn{id=Id, amount=Amount,
						new_balance=NewBalance,transaction_date=erlang:localtime()};
		true ->
			#bank_account_payment_declined{id=Id,amount=Amount,
						transaction_date=erlang:localtime()}
		end,
	apply_new_event(Event, State);
```

The first line is where you try to withdraw money. How is handled here the concurrency? 
I mean I can have two concurrent operations on the same bank account but here I don't see 
this check here. Is the system running all commands sequentially so that state doesn't get corrupted?