none	No methods, only access via object<->slot
get	Get access, only write through object->slot
send	Send access, only read through object<-slot
both	Both read and write access

If a variable requires side-effects for writing (the most common case), it should be declared with variable<-access: read and a send_method with the same name should be defined on the class. This method may write the variable using object->slot.