Dfd cont example when a client wants to purchase a

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Unformatted text preview: n actor is the one who actually interacts with the system whether or not that actor is the original source of information 30 • Actors should be named with a noun or noun phrase 29 Use Case Diagram vs. DFD (cont.) • Example: When a client wants to purchase a stock, he/she may call an agent and the agent will enter an order to the stock trading system on behalf of the client • In DFD, the client would be identified as an external entity; the agent’s activity would be embedded in a process “Enter client’s order” and the agent would NOT be identified as an external entity • In the use case diagram, the agent would be identified as the actor who uses the system to enter a client’s order • Thus, it is important to identify every possible role that will use the system 31 Actor Types • Primary Actor: – One who receives value from the system – One who has a goal requiring the assistance of the system system • Secondary Actor – One who provides service to the system in the use case – One from which the system needs assistance to help primary actors achieve their goals 32 Actor Personalities • Initiator: an actor who initiates events that trigger a use case (e.g., customer places an order) • External Server: an actor who provides a service to the system in the use case (e.g., query to a credit bureau to process a loan) • Receiver: an actor that receives information from the use case (e.g. IRS receives corporate tax return) • Facilitator: an actor that supports another actor’s interaction with the system (e.g., data entry clerks) 33 Abstract Actors • An abstract actor represents several kinds of actors who use use the system in the same way and play the same role • It is seldom used Student (Abstract) UG Student (Concrete) PG Student (Concrete) 34 Actor Specification Card Actor Specification Actor Name: Customer Type: Primary Personality: Initiator Abstract: No Role Description: A customer is a person who has opened an account with the bank. The customer is the main reason for the existence of ATM machines. The customer interacts with the ATM to obtain convenient banking services at times when he/she cannot or is not convenient to obtain such services at the bank’s premises. premises. Actor Goals (a goal will map to one or more use cases below): Context Diagram • It is a representation of the system boundary and all the actors that interact with the system • Actors are represented as stick figures with a label in...
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This note was uploaded on 12/22/2010 for the course ISOM ISOM221 taught by Professor Sheunhhee during the Spring '09 term at HKUST.

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