Connie's Convenience Store - About Peter Coad
Connie's Convenience Store - About Peter Coad
Connie's Convenience Store - About Peter Coad
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10 Connie’s <strong>Convenience</strong> <strong>Store</strong> Selecting Problem-Domain Objects<br />
Customer<br />
What about the customer? Adding “customer” makes sense only if you have some<br />
way to find out who Connie’s customers are, or at least who some of her customers are.<br />
#47. “Way to Know” Strategy selecting objects (consider and challenge)<br />
• You need a way to know each object—and its attribute values.<br />
• If you have no way to know an object, either find a way to know about it or<br />
put the object in the “not this time” model component.<br />
• Example: customer. You must have a way to know about customer objects;<br />
otherwise, put customer in the “not this time” model component.<br />
If each and every customer comes into a store, participates anonymously, and<br />
leaves again, then there is no reason to have a customer object in an object model.<br />
Why? Because the system would not be responsible to know or do anything about that<br />
customer.<br />
But what if Connie’s new system could know the identity of at least some of her<br />
customers, especially some of her better customers? What then?<br />
How could Connie’s cashiers find out about who their customers are? What could<br />
Connie do to make this happen? She could offer a check guarantee card. Or she could<br />
launch a special “frequent shopper” program. Either way, Connie could issue cards with<br />
machine-readable codes. The cashier (or even the shopper) could run the card through a<br />
scanner.<br />
Connie could use that information to better serve her customers.<br />
This looks like a change in scope. Better check it out with Connie.<br />
(<strong>Peter</strong>) How about a frequent buyer program?<br />
(Connie) Nice idea. But not this time! I’m dealing with enough changes right now.<br />
(<strong>Peter</strong>) Understood. Have a nice day.<br />
(<strong>Peter</strong>, to himself) And don’t be so cranky. Good grief. I’m just doing my job.<br />
Okay, then. To the problem-domain component, add person and cashier. To the “not<br />
this time” component, add organization, customer, and head cashier (Figure 1–4):<br />
ProblemDomain<br />
Cashier<br />
Person<br />
NotThisTime<br />
Customer<br />
HeadCashier<br />
Organization<br />
Person<br />
Figure 1–4: Select actors and participants.<br />
Cashier
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