(responding to Eric D. Tarkington)
>...or anyway, I think it's 4. It's been such a long time since my last > one. > > As usual, the bar bet is on a controversial question that should be > obvious to everyone, dammit, but the instructors at Seneca College > disagree with each other. I will try to state opposing positions > even-handedly, and will only confess my "side" only after others have > stated some opinions. > > Here's the bet: In sequence diagrams, you should not send messages to > actors. > > THIS IS OBVIOUSLY TRUE! When you send a message in a sequence diagram, > you are saying that the receiving object has an operation. This is > probably the main payoff of sequence diagrams: they reveal the > operations and how to coordinate them. Actors are either human or just > external, and we can't build operations into them either way. This is a > basic difference between actors and objects. > > THIS IS OBVIOUSLY CRAP! When you send a message to an actor, you are > showing necessary timing relationships between messages, which is a > crucial feature of correct sequence diagrams. End of discussion. > > OK, folks, what do you think? There is a virtual beer in it for a > correct answer, but you have to make a clear winning argument! You have a Use Case. It has two Actors. Draw a top-level sequence diagram for the interactions. For one of the Actors, its involvement is easy, it initiates the Use Case and can receive information in the 'return message'. (like it or not, I'm sticking with that...) For the other Actor, the only way to describe its involvement is by sending it a message. (Okay, I've got work-rounds too, but...) Humans have interfaces too. They are known as the five senses. So we don't need to go down to that level of detail, but we _can_ send messages to Actors, even when they are Human. Further, we don't build the operations for any external system, particularly human ones (mothers, feel free to differ...), we just tailor our communication to an agreed external interface. Finally, pragmatism rules OK. I don't care what the rule book says, I find it useful to sent messages to Actors, and it aids in communicating ideas between members of my teams. Leave the academics to their academic arguments, add the cost of the beer to their bar tab, enjoy it and get back to some real work ;-) Paul Oldfield any opinions expressed herein are not necessarily those of Mentors of Cally ************************************************************************ * Rose Forum is a public venue for ideas and discussions. * For technical support, visit http://www.rational.com/support * * Post or Reply to: [EMAIL PROTECTED] * Subscription Requests: [EMAIL PROTECTED] * Archive of messages: * http://www.rational.com/support/usergroups/rose/rose_forum.jsp * Other Requests: [EMAIL PROTECTED] * * To unsubscribe from the list, please send email * To: [EMAIL PROTECTED] * Subject: <BLANK> * Body: unsubscribe rose_forum *************************************************************************
