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Microsoft PowerPoint - Lecture 7 IS421 Systems Analysis Requirements Specifications pSDL SDLC - Process pSDL Project Management Business Case 1 2 3 4 Last Lecture: Use-Case Diagrams This Lecture: Activity Diagrams and SD Requirements spcifications & Object-Oriented Analysis & Design 1. Use-Cases Diagram and text 3. Activity Diagrams 2. System Sequence Diagrams 4. Class Diagrams 5. Package Diagrams Last Lecture: Use-Case Diagrams This Lecture: SD and Activity Diagrams We will discuss this today We will discuss this today Capturing & Documenting Requirements Capturing & Documenting Requirements Use-Case Diagram Activity Diagram Use-Case Diagram Use-Case Scenario System Sequence Diagram 6 Requirements Diagrams With UML Models 1 2 4 3 Last Lecture we discussed 1 & 2. This lecture we will discuss 3&4 7 UML Diagrams used for Modeling 8 UML Diagram: http://www.uml-diagrams.org 9 Which one came first? Math/Calculus or Physics Picture or Text 10 Activity Diagrams – to document Information Gathered Activity Diagrams: Unobtrusively observe business processes Diagram all information gathered Sample diagram: representation of workflow Identify agents to create the appropriate swimlanes Represent steps of workflow with appropriate ovals Connect activity ovals with arrows to show direction Use decision symbol to represent either/or situation Use synchronization bars for parallel paths Object Modeling with the Unified Modeling Language An activity diagram shows the actions and events involved in withdrawing cash from an ATM machine. Activity Diagrams Shows the actions and events as they occur Show the order in which the actions take place and identify the outcomes 12 A Simple Activity Diagram to Demonstrate a Workflow What we really want? We want to know How to capture a Workflow What is an Activity Diagram? It is a type of behavioral diagram in UML. An activity diagram visually presents a series of actions or flow of control in a system similar to a flowchart and a data flow diagram. They are used to model computational and organizational processes. They can also describe the steps in a use case diagram. Activities modeled can be sequential and concurrent. Notations and Symbols Initial State or Start Point: A small filled circle followed by an arrow represents the initial action state or the start point for any activity diagram. Final State or End Point:An arrow pointing to a filled circle nested inside another circle represents the final action state. Action Flow: Action flows, also called edges and paths, illustrate the transitions from one action state to another. Notations and Symbols Object Flow: Object flow refers to the creation and modification of objects by activities. An object flow arrow from an action to an object means that the action creates or influences the object. An object flow arrow from an object to an action indicates that the action state uses the object. Activity or Action State: An action state represents the non-interruptible action of objects. Notations and Symbols Decisions and Branching: A diamond represents a decision with alternate paths. Guards: In UML, guards are a statement written next to a decision diamond that must be true before moving next to the next activity. These are not essential, but are useful when a specific answer, such as "Yes, three labels are printed," is needed before moving forward. Notations and Symbols Synchronization: A fork node is used to split a single incoming flow into multiple concurrent flows. It is represented as a straight, slightly thicker line in an activity diagram. A join node joins multiple concurrent flows back into a single outgoing flow. A fork and join mode used together are often referred to as synchronization. Notations and Symbols Time Event: This refers to an event that stops the flow for a time; an hourglass depicts it. Merge Event: A merge event brings together multiple flows that are not concurrent. Notations and Symbols Sent and Received Signals: Signals represent how activities can be modified from outside the system. They usually appear in pairs of sent and received signals, because the state can't change until a response is received, much like synchronous messages in a sequence diagram. For example, an authorization of payment is needed before an order can be completed. Interrupting Edge: An event, such as a cancellation, that interrupts the flow denoted with a lightning bolt. Notations and Symbols Swimlanes: Swimlanes group related activities into one column Customer Order Case Study Customer Order Case Study Visio 23 An Activity Diagram Showing Concurrent Paths 24 Knowledge Applied with Walkthrough Examples 25 Use Case Detailed Descriptions Fully developed use case description Superset of intermediate and brief descriptions Consists of eleven compartments User, actor, stakeholder, EBP, and conditions identified Activity Diagram Description Document the workflows of business processes Document flow of activities for use case scenarios Form basis of system sequence diagrams (SSDs) 26 Fully Developed Description of Telephone Order Scenario for Create New Order Use Case 27 Activity Diagram of the Telephone Order Scenario Sequence Diagrams Sequence diagram A sequence diagram is a way of drawing a picture of a scenario Sequence diagrams are also sometimes called event trace diagrams, ladder diagrams, interaction diagrams, or fence post diagrams Each vertical line describes an “actor” or a “system” in the scenario The vertical axis represents time: time flows down the page Postal clerk Ask for book of stamps Customer No Do you want anything else? Respond with price Give stamps and change Give money 30 Object Modeling with the Unified Modeling Language Sequence Diagrams A dynamic model of a use case, showing the interaction among classes during a specified time period Graphically documents the use case by showing the classes, the messages, and the timing of the messages Include symbols that represent classes, lifelines, messages, and focuses Object Modeling with the Unified Modeling Language A sequence diagram with two classes. Notice the X that indicates the end of the CLASS 2 lifeline. Also notice that each message is represented by a line with a label that describes the message, and that each class has a focus that shows the period when messages are sent or received Classes Identified by a rectangle with the name inside Classes that send or receive messages are shown at the top of the sequence diagram Lifelines Identified by a dashed line The lifeline represents the time during which the object above it is able to interact with the other objects in the use case An X marks the end of the lifeline Messages Identified by a line showing direction that runs between two objects The label shows the name of the message and can include additional information about the contents Focuses Identified by a narrow vertical shape that covers the lifeline The focus indicates when an object sends or receives a message Object Modeling with the Unified Modeling Language The sequence diagram for the ADD NEW STUDENT use case. System Sequence Diagrams What is a Sequence Diagram The Sequence Diagram models the collaboration of objects based on a time sequence. It shows how the objects interact with others in a particular scenario of a use case. Resources Requirement analysis and high level design. Model the context of a system. What is a System Sequence Diagram System sequence diagram (Use case model) It is a special case of sequence diagrams Captures the sequence of events between the actor (primary or external) and the system System is treated as Black box 36 Notations and Symbols Actors: Actors are the entities that interact with a system. Although in most cases, actors are used to represent the users of system, actors can actually be anything that needs to exchange information with the system. So, an actor may be people, computer hardware, other systems, etc. Notations and Symbols Class Roles or Participants: Class roles describe the way an object will behave in context. Messages: Messages are arrows that represent communication between objects. Use half-arrowed lines to represent asynchronous messages. Notations and Symbols Lifelines: Lifelines are vertical dashed lines that indicate the object's presence over time. Activation or Execution Occurrence: Activation boxes represent the time an object needs to complete a task. Notations and Symbols Synchronous Message: A synchronous message requires a response before the interaction can continue. Asynchronous Message: Asynchronous messages don't need a reply for interaction to continue. Reply or Return Message: A reply message is drawn with a dotted line and an open arrowhead pointing back to the original lifeline. How to create a Sequence Diagram in Visio Clerk-System Interaction 42 43 Clerk-System Interaction Visio Clerk-System Interaction 44 45 Clerk-System Interaction Visio Clerk-System Interaction (Order Placing) 46 47 Clerk-System Interaction (Order Placing) Visio 48 Process Sale Scenario 49 Sample SSD in Visio 50 SSD A system sequence diagram (SSD) is a fast and easily created artifact that illustrates input and output events related to the systems under discussion. They are input to operation contracts and most importantly object design. 51 SSD The use case text and its implied system events are input to SSD creation. The SSD operations can in turn be analyzed in the operation contracts, detailed in the Glossary, and most important serve as the starting point for designing collaborating objects. An SSD shows, for a particular course of events within a use case, the external actors that interact directly with the system, the system (as a black box), and the system events that the actors generate. Use Cases and System Sequence Diagrams A use case is a prose description of an actor/system interaction. Use case diagram is a visual summary of: All significant use cases. All significant actors. Relations among actors and use cases. A System sequence diagram (SSD) is a visual summary of the individual use cases. For ease of understanding, each use-case scenario corresponds to a separate system sequence diagram. Characteristics of System Sequence Diagrams System sequence diagrams are a special case of the more- general UML sequence diagram. Captures the sequencing of messages and data exchanged between an actor and the system. Provides about the same level of detail as use-case prose description. Usually deals with primary actors and system, but can include other actors as well. Provides a more formal notation for expressing the interaction. Concerned only with external behavior: the system is treated as