CS551 Interaction Models (Chapter 4 of UML)

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CS551 Interaction Models (Chapter 4 of UML)

• Yugi Lee
• STB 555
• [phone]
• yugi_at_cstp.umkc.edu
• www.cstp.umkc.edu/yugi

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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.

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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.

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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.

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Action Type and Refinement
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action Wholesaler sell (retailer Retailer,
item Item, out price ) pre
catalog.stock-gtincludes(item) -- this item was
part of our stock post price
item.product.price -- price returned to caller
and cash cash_at_pre price and
stock stock_at_pre item
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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

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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 300-500 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

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Concurrent Actions

• operation action (retailer, wholesaler) supply
• -- a condition maintained while an action
  occurrence is in progress.
• guarantee retailer.stock-gtsize gt10
• -- true throughout the action occurrence for all
  of this description to be applicable.
• rely wholesaler.in_business

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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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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 wholesalers invoice

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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.