CS551 - Lecture 7 1 CS551 Interaction Models (Chapter 4 of UML) Yugi Lee STB #555 (816)

2 CS551 - Lecture 7 Important Questions in OO Design What should the system do? –type specification, putting it together. What objects should be chosen? –type specification, modified by design patterns to improve decoupling. Which object should do what, and how should the objects interact? –separate different concerns into different objects while balancing the needs of decoupling with performance.

3 CS551 - Lecture 7 Collaboration/Type A type represents a specification of the behavior seen at an interface to an object. A collaboration is a design for the way objects interact with one another to achieve a mutual goal. –a group of participating objects –what goes on inside a software component. –how actors interact with the component. –how real world objects interact with one another.

4 CS551 - Lecture 7 Joint Actions Localized Actions: operations –a one-sided specification of an action, focused entirely on a single object and how it responds to a request. Joint Actions: use-cases –abstract multiple interactions and specific protocols –the net effect on all participants and the summary of information exchanged –The interacting participants might be objects inside a program, people, or computers.

5 CS551 - Lecture 7 Action Type and Refinement

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7 action Wholesaler :: sell (retailer : Retailer, item : Item, out price : $) pre catalog.stock->includes(item) -- this item was part of our stock post price = item.product.price -- price returned to caller and cash = + price and stock = – item

8 CS551 - Lecture 7 Use Cases are Joint Actions A joint action with multiple participant objects that represent a meaningful business task. use case sale participants: retailer, wholesaler parameters: set of items pre: the items must be in stock, retailer must be registered, retailer must have cash to pay post: retailer has received items and paid cash wholesaler has received cash and given items

9 CS551 - Lecture 7 Refinement of Use Cases use case sale..... priority primary concurrent many concurrent sales with different wholesaler reps no sale and return by the same retailer at the same time refinement criteria -- what to consider when refining this use case into a sequence frequency per day performance less than 3 minutes per sale use case telephone sale by distributor refines use case sale 1. retailer calls wholesaler and is connected to rep 2. rep gets distributor membership information from retailer 3. rep collects order information from retailer, totaling the cost 4. rep confirms items, total, and shipping date with wholesaler 5. both parties hang up 6. shipment arrives at retailer 7. wholesaler invoices retailer 8. retailer pays invoice abstract result sale was effectively conducted with amount of the order total and items as ordered

10 CS551 - Lecture 7 Concurrent Actions operation action (retailer, wholesaler) :: supply -- a condition maintained while an action occurrence is in progress. guarantee retailer.stock->size >10 -- true throughout the action occurrence for all of this description to be applicable. rely wholesaler.in_business

11 CS551 - Lecture 7 Sequence Diagrams with Actions Action occurrence –an interaction between two particular points in time involving specific participant objects bringing about a change of state in some or all of them. Sequence diagram –a graphical representation of action occurrences –a horizontal bar (with arrows or ellipses) –Starting from the initial state, each action occurrence in a scenario causes a state change.

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13 CS551 - Lecture 7 Scenario A scenario is a particular trace of action occurrences scenario order fulfillment out of stock initial state: retailer has no more items of product p1; wholesaler has no inventory of p1 either steps 1 retailer places an order for quantity q of p1 2 wholesaler orders p1 from manufacturer m 3 wholesaler receives shipment of p1 from m 4 wholesaler ships q1 of p1 to retailer with invoice 5 retailer pays wholesaler’s invoice

14 CS551 - Lecture 7 Collaboration Specification A collaboration abstracts multiple participants –consider all the participants in an operation, because its outcome may affect and depend on all of them (defer the partitioning of responsibility when needed) –the list of actions between the collaborators –an optional list of actions considered “outside” the collaboration (generalize action occurrences to permit multiparty actions) –action specs (the pre and/or post spec of an action may reflect the change of state of all its participants) –static and effect invariants that may apply to either set of actions –an optional sequence constraint on the set of actions.