Lecture Requirement engineering Chapter 4 Requirement analysis

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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
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