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Lecture Requirement engineering Chapter 4 Requirement analysis. This chapter provides knowledge of data flow diagram, use case modelling and use case diagram. Lecture Requirement engineering Chapter 4 Requirement analysis. This chapter provides knowledge of data flow diagram, use case modelling and use case diagram.
DFD definition DFD components DFD Key definition DFD level Data flow diagram shows business processes and the data that flows between them Data flow modeling takes a functional decomposition approach to systems analysis, breaking complex problems into progressive levels of detail 2 type of DFD Logical process models describe processes without suggesting how they are conducted Physical models include information about how the processes are implemented The DFD is a diagram that consists principally of four symbols, namely the external entity, the data flow, the process and the data store Additionally, a physical flow can be shown on the DFD of the current system External entity: are those things that are identified as needing to interact with the system under consideration Gane and Sarson Symbol DeMarco and Yourdan Symbol Example Process: an activity that receives data and carries out some form of transformation or manipulation before outputting Naming convention of a process: Name of a system Name of a subsystem A verb Process: an activity that receives data and carries out some form of transformation or manipulation before outputting Gane and Sarson Symbol DeMarco and Yourdan Symbol Data flow: Data move in a specific direction from an origin to a destination Gane and Sarson Symbol DeMarco and Yourdan Symbol Primary actor: has a user goals filfilled through using services of the systems Supporting actor: provides service to the system Offstage: interested but not directly involved Ex: the tax agency Choose the system boundary Identify primary actors Identify goals for each primary actor Define use cases in terms of user goals The EBP (elementary business process) test: a task performed by one person in one place at one time, in response to a business event, which adds measurable business value and leaves the data in a consistent state, e.g Approve Credit or Price Order A common use case mistake Defining many use cases at too low a levell that is as a signle step, subfunction, or subtask within an EBP The EBP (elementary business process) test: a task performed by one person in one place at one time, in response to a business event, which adds measurable business value and leaves the data in a consistent state, e.g Approve Credit or Price Order A common use case mistake Defining many use cases at too low a levell that is as a signle step, subfunction, or subtask within an EBP System name Represents the scope of the subject, e.g., a system or an individual business process Includes the name of the subject inside or on top is Actor/Role a user or external system with which a system being modeled interacts Are placed outside the system boundary Represents a major piece of system functionality Use case Is placed inside the system boundary Is labeled with a descriptive verb-noun phrase Actor – Actor: Generalization Actor - use case: Association Use case – use case: Generalization Include Extend Actor – Actor: Generalization: An actor may specialize multiple actors, and an actor may be specialized by multiple actors Sinh viên Sinh viên tốt nghiệp Sinh viên chưa tốt nghiệp Actor – Use case: Association: it indicates that the actor communicates with the system and participates in the use case base Use case – Use case: Extend : the extension use case will extend (or be inserted into) and augment the base use case extending base Use case – Use case: Include: indicates that the base use case will include or call the inclusion use case included Đăng ký HP Đăng nhập Use case – Use case: Generalization: address this situation by factoring out and reusing similar behavior from multiple use cases ... Context Diagram can be drawn by following steps: Step - List the documents used in the system Step - List all the sources & recipients Step - Draw a box representing the system and show the flow... Language) provides a common vocabulary of object-oriented terms and diagramming techniques that is rich enough to model any systems development project from analysis through implementation Use cases... implementation Use cases are text stories that are useful for discovering and recording requirements Use-case modeling is primarily an act of writing text, not drawing diagrams UML defines