Chapter 4: Business Process and Functional Modeling PDF

Chapter 4: Business Process and Functional Modeling  Objectives ⚫ Understand the process used to identify business processes and use cases. ⚫ Understand the process used to create use-case diagrams ⚫ Understand the process used to model business processes with act...

Chapter 4: Business Process and Functional Modeling  Objectives ⚫ Understand the process used to identify business processes and use cases. ⚫ Understand the process used to create use-case diagrams ⚫ Understand the process used to model business processes with activity diagrams. ⚫ Understand the rules and style guidelines for activity diagrams. ⚫ Understand the process used to create use case descriptions. ⚫ Understand the rules and style guidelines for use case descriptions. ⚫ Be able to create functional models of business processes using use-case diagrams, activity diagrams, and use case descriptions.  Introduction ⚫ Now begin the process of turning the requirements into functional models ⚫ Models are logical; i.e., independent of how they are implemented (manual or computerized) ⚫ Develop use-cases from the requirements ⚫ Use-case: how a system interacts with its environment ⚫ Includes a diagram and a description to depict the discrete activities that the users perform ⚫ Develop activity diagrams from the use-cases ⚫ These model the business processes or how a business operates ⚫ Used to illustrate the movement of objects (data) between activities  Business Process Identification With Use-Cases ⚫ Elements of Use-Case Diagrams ⚫ Actors: users or other interacting systems ⚫ Associations: lines to connect actors and use-cases ⚫ Interactions, inclusions, extensions or generalizations ⚫ Use-case: a major process in the system that gives a benefit to the users ⚫ Subject boundary: a named box that depicts the scope of the system  Identifying Major Use-Cases ⚫ Review the requirements definition ⚫ Identify the subjectʼs boundaries ⚫ Identify the primary actors and their goals ⚫ Identify the business processes and major use-cases ⚫ Carefully review the current set of use-cases ⚫ Split or combine some to create the right size ⚫ Identify additional use-cases Create a Use-Case Diagram ⚫ Place & draw the use-cases ⚫ Place & draw the actors ⚫ Draw the subject boundary ⚫ Add the associations Example Use-Case ⚫ Library circulation system  BPM With Activity Diagrams ⚫ Business processes consist of a number of activities ⚫ Activity diagrams depict the sequence of these activities ⚫ Diagrams are abstract and describe processes in general ⚫ They model behavior independent of objects ⚫ Can be used for any type of process  Activity Diagram Syntax Action or Activity – Represents action or set of actions Control Flow – Shows sequence of execution Initial Node – The beginning of a set of actions Final Node – Stops all flows in an activity Decision Node – Represents a test condition  Elements of an Activity Diagram ⚫ Actions & Activities ⚫ Something performed for some specific business reason ⚫ Named with a verb and a noun (e.g., Get Patient Information) ⚫ Activities can be further sub-divided; actions cannot ⚫ Object Nodes: represent the flow of information from one activity to another ⚫ Control Flows: model execution paths ⚫ Object Flows: model the flow of objects ⚫ Control Nodes: 7 types  Control Nodes ⚫ Initial node: the beginning of the set of actions/activities ⚫ Final-activity node: stops all actions/activities ⚫ Final-flow node: stops one execution path but allows others to continue ⚫ Decision node: represents a test to determine which path to use to continue (based on a guard condition) ⚫ Merge node: rejoins mutually exclusive execution paths ⚫ Fork node: separates a single execution path into one or more parallel paths ⚫ Join node: rejoins parallel execution paths Activity Diagram Symbols Sample Activity Diagram  Swimlanes ⚫ Used to assign responsibility to objects or individuals who actually perform the activity ⚫ Represents a separation of roles among objects ⚫ Can be drawn horizontally or vertically Guidelines for Activity Diagrams 1. Set the scope of the activity being modeled 2. Identify the activities; connect them with flows 3. Identify any decisions that must be made 4. Identify potential parallelism in the process 5. Draw the activity diagram  Creating an Activity Diagram ⚫ Choose a business process identified previously ⚫ Review the requirements definition and use-case diagram ⚫ Review other documentation collected thus far ⚫ Identify the set of activities used in the business process ⚫ Identify control flows and nodes ⚫ Identify the object flows and nodes ⚫ Lay out & draw the diagram (minimize crossing lines)  Use Cases ⚫ The primary driver for all UML diagramming techniques ⚫ Depicts activities performed by the users ⚫ Describe basic functions of the system: ⚫ What the user can do ⚫ How the system responds ⚫ Use cases are building blocks for continued design activities ⚫ Each use-case describes 1 and only 1 function Types of Use Cases  Elements of a Use Case Description Overview: Name, ID Number, Type, Primary Actor, Brief Description, Importance Level, Stakeholder(s), Trigger(s) Relationships: Association: Communication between the use case and the actors Extend: Extends the functionality of a use case Include: Includes another use case Generalization: Allows use cases to support inheritance Flow of events Normal flow: the usual set of activities Sub-flows: decomposed normal flows to simplify the use-case Alternate or exceptional flows: those not considered the norm Optional characteristics (complexity, time, etc.)  Use Case Writing Guidelines 1. Write in the form of subject-verb-direct object 2. Make sure it is clear who the initiator of the step is 3. Write from independent observerʼs perspective 4. Write at about the same level of abstraction 5. Ensure the use case has a sensible set of steps 6. Apply the KISS principle liberally. 7. Write repeating instructions after the set of steps to be repeated  Creating Use-Case Descriptions 1. Pick a high priority use-case and create an overview: ⚫ List the primary actor ⚫ Determine its type (overview or detail; essential or real) ⚫ List all stakeholders and their interests ⚫ Determine the level of importance of the use-case ⚫ Briefly describe the use-case ⚫ List what triggers the use-case ⚫ List its relationship to other use-cases 2. Fill in the steps of the normal flow of events required to complete the use-case  Creating Use-Case Descriptions (cont.) 3. Ensure that the steps listed are not too complicated or long and are consistent in size with other steps 4. Identify and write the alternate or exceptional flows 5. Carefully review the use-case description and confirm that it is correct 6. Iterate over the entire set of steps again Example Use-Case Description  Verifying & Validating a Use-Case ⚫ Use-cases must be verified and validated before beginning structural and behavioral modeling ⚫ Utilize a walkthrough: ⚫ Perform a review of the models and diagrams created so far ⚫ Performed by individuals from the development team and the client (very interactive) ⚫ Facilitator: schedule and set up the meeting ⚫ Presenter: the one who is responsible for the specific representation being reviewed ⚫ Recorder (scribe) to take notes and especially to document errors  Rules for Verification & Validation 1. Ensure one recorded event in the flows of the use-case description for each action/activity on the activity diagram 2. All objects in an activity diagram must be mentioned in an event of the use-case description 3. The sequence of the use-case description should match the sequence in the activity diagram 4. One and only one description for each use-case 5. All actors listed in a use-case description must be shown on the use-case diagram 6. Stakeholders listed in the use-case description may be shown on the use-case diagram (check local policy) 7. All relationships in the use-case description must be depicted on the use-case diagram 8. All diagram-specific rules must be enforced  Summary ⚫ Presented in this chapter: ⚫ The identification of business processes using use-case diagrams and descriptions ⚫ Modeling business processes with activity diagrams ⚫ How to create the documentation of use-cases and use-case descriptions ⚫ How to verify and validate the business processes and functional models