Connie's Convenience Store - About Peter Coad

Selecting Problem-Domain Objects Connie’s Convenience Store 13
#34. “Select Kinds of Objects” Strategy selecting objects (kinds of objects)
• Use generalization-specialization (gen-spec) to find additional classes.
Look at each class as a generalization. Name its specializations, ones that fit with
system objectives.
Look at each specialization. Name its generalizations, ones that fit within system
objectives.
• Use gen-spec for domain-based reuse within an application; use configuration
management for reuse across multiple applications, even multiple problem domains.
• Use gen-spec to show domain-based “what’s the same, what’s different,” within an
application.
• Examples: equipment, kinds of equipment; participants, kinds of participants;
transactions, kinds of transactions.
A store is a kind of sales outlet. Perhaps over time, Connie will expand to other
kinds of sales outlets (for example, catering centers or catalog sales). Connie might
choose to do this in the future.
Stores might be specialized into kinds of stores (for example, superstore, grocery
store, convenience store). Connie might choose to do this in the future, too.
Note how generalization-specialization is a useful tool for exploring what could
happen, with success over time.
For now, leave store as is.
Select things
Tangible things
#16. “Select Tangible Things” Strategy selecting objects (pattern players)
• Look for tangible objects, ones used in the problem domain.
• Take a walk through the business. Select objects from the tangible ones around you.
• Examples: account, cash box, cash drawer, item, plan, procedure, product, schedule,
scheduled event.
What are the tangible things in the store?
– item
– register
– cash drawer.