and the seller so the the two users that are uh currently participants of this conversation so looking at this conversation can have also additional attributes but we could already maybe uh simplify this so we can have a conversation that has a seller and a buyer and both of them are specified the specific research types so we can sell it with the type seller buyer with the type buyer but also we can reuse them because looking at both of these user types they can be type of user so we reduce the number of special