chap7 需求分析-用例图.ppt
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1、chap7 需求分析需求分析-用例用例图图Copyright 2004 The McGraw-Hill Companies. All Rights reservedAn Introduction to Use-Case Modeling 简介简介 One of the primary challenges in a system design process is the ability to elicit(提取提取) the correct and necessary system requirements from the stakeholders and specify them in
2、a manner understandable to them so those requirements can be verified and validated.系统开发过程的首要问题系统开发过程的首要问题是正确地提取用户需求,并是正确地提取用户需求,并以用户能够理解的方式进行表达,以便他们他们能够以用户能够理解的方式进行表达,以便他们他们能够核实并确认核实并确认Copyright 2004 The McGraw-Hill Companies. All Rights reservedAn Introduction to Use-Case Modeling 简介简介 传统的建方法:传统的建
3、方法: Data and process models Prototypes requirement specifications 问题:问题:设计者理解而用户不理解设计者理解而用户不理解 Leads to scope creep(范围蔓延)(范围蔓延), schedule creep (进度蔓延)进度蔓延), cost overruns(成本超支)(成本超支).Copyright 2004 The McGraw-Hill Companies. All Rights reservedUser-Centered Development and Use-Case Modeling以用户为中心的系统
4、开发与用例建模Copyright 2004 The McGraw-Hill Companies. All Rights reservedUser-Centered Development User-centered development a process of systems development based on understanding the needs of the stakeholders and the reasons why the system should be developed.系统开发建立应在理解用户需求之上系统开发建立应在理解用户需求之上Copyright 2
5、004 The McGraw-Hill Companies. All Rights reservedUse-Case Modeling 用例建模用例建模 Use-case modeling the process of modeling a systems functions in terms of 针对系统功能进行建针对系统功能进行建模:模: business events:有哪些业务事件?:有哪些业务事件? who initiated the events:谁发起了这些事件?:谁发起了这些事件? and how the system responds to those events:系统:
6、系统将如何响应这些事件?将如何响应这些事件?Copyright 2004 The McGraw-Hill Companies. All Rights reservedSample Use-Case Model DiagramCopyright 2004 The McGraw-Hill Companies. All Rights reservedBenefits of Use-Case Modeling Provides a tool for capturing functional requirements(获取功能获取功能需求需求). Provides a means of communic
7、ating with users and other stakeholders concerning system functionality in a language that is easily understood.(便于沟通)(便于沟通) Provides a tool for requirements traceability(需求跟踪需求跟踪). Provides a framework for driving the system development project. (提供一个驱动系统开发项目的框架)(提供一个驱动系统开发项目的框架)Copyright 2004 The
8、McGraw-Hill Companies. All Rights reservedSystem Concepts for Use-Case Modeling Use-case diagram describes who will use the system and in what ways the user expects to interact with the system. 用例图用例图描述系统与外部系统或用户之间的交互图描述系统与外部系统或用户之间的交互图 Use-case narrative a textual description of the business event
9、and how the user will interact with the system to accomplish the task.用例说明用例说明针对用例执行过程的文本说明针对用例执行过程的文本说明 Use case a behaviorally related sequence of steps (a scenario), both automated and manual, for the purpose of completing a single business task.用例用例从外部使用者的角度描述系统功能,是一系列相关从外部使用者的角度描述系统功能,是一系列相关的操作
10、步聚,共同完成单一的工作任务。的操作步聚,共同完成单一的工作任务。Copyright 2004 The McGraw-Hill Companies. All Rights reservedSample Use-Case Model DiagramCopyright 2004 The McGraw-Hill Companies. All Rights reservedBasic Use-Case Symbols Use case (用例)(用例) subset of the overall system functionality Represented graphically by a hor
11、izontal ellipse(椭园)(椭园) with the name of the use case appearing above, below, or inside the ellipse. Actor (参与者)(参与者) anything that needs to interact with the system to exchange information. Could be a human, an organization, another information system, an external device, or even time. Temporal eve
12、nt (时间事件时间事件) a system event triggered by time. The actor is time.Copyright 2004 The McGraw-Hill Companies. All Rights reservedFour Types of Actors Primary business actor The stakeholder that primarily benefits from the execution of the use case. e.g. the employee receiving the paycheck Primary syst
13、em actor The stakeholder that directly interfaces with the system to initiate or trigger the business or system event. e.g. the bank teller entering deposit information External server actor The stakeholder that responds to a request from the use case. e.g. the credit bureau authorizing a credit car
14、d charge External receiver actor The stakeholder that is not the primary actor but receives something of value from the use case. e.g. the warehouse receiving a packing slipCopyright 2004 The McGraw-Hill Companies. All Rights reservedUse Case Association Relationship Association(关联关联) a relationship
15、 between an actor and a use case in which an interaction occurs between them. Association modeled as a solid line connecting the actor and the use case. Association with an arrowhead touching the use case indicates that the use case was initiated by the actor. Association lacking arrowhead indicates
16、 a receiver actor. 无箭头则表示一个接收者无箭头则表示一个接收者 Associations may be bidirectional or unidirectional.Copyright 2004 The McGraw-Hill Companies. All Rights reservedUse Case Extends Relationship Extension use case(扩展用例)(扩展用例) a use case consisting of steps extracted from a more complex use case in order to si
17、mplify the original case and thus extend its functionality. Relationship between the extension use case and the use case it is extending is called an extends relationship. Represented as an arrowheaded line beginning at the extension use case and point to the use case it is extending. Each extends r
18、elationship line is labeled “.”Copyright 2004 The McGraw-Hill Companies. All Rights reservedUse Case Uses Relationship Abstract use case a use case that reduces redundancy(冗余冗余) among two or more other use cases by combining the common steps found in those cases.Relationship between the abstract use
19、 case and the use case that uses it is called a uses (or includes) relationship.Depicted as an arrow headed line beginning at the original use case and pointing to the use case it is using. Each uses relationship line is labeled “.”Copyright 2004 The McGraw-Hill Companies. All Rights reservedUse Cas
20、e Depends On RelationshipDepends On a use case relationship that specifies which other use cases must be performed before the current use case. Can help determine sequence in which use cases need to be developed. Depicted as an arrow headed line beginning at one use case and pointing to a use case i
21、t is dependent on. Each depends on relationship line is labeled “.”Copyright 2004 The McGraw-Hill Companies. All Rights reservedUse Case Inheritance RelationshipInheritance(继承继承) a use case relationship in which the common behavior of two actors initiating the same use case is extrapolated and assig
22、ned to a new abstract actor to reduce redundancy. Other actors can inherit the interactions of the abstract actor. Depicted as an arrowheaded line beginning at one actor and pointing to the abstract actor whose interactions the first actor inherits. Copyright 2004 The McGraw-Hill Companies. All Righ
23、ts reservedThe Process of Requirements Use-Case ModelingSteps步骤步骤 Identify business actors (参与者参与者). Identify business use cases (用例用例). Construct use-case model diagram (用例模型图用例模型图).1. Documents business requirements use-case narratives (用例说明用例说明).Copyright 2004 The McGraw-Hill Companies. All Right
24、s reserved案例背景:案例背景:Soundstage Entertainment Club 传统广告:传统广告:“1便士任选便士任选10盘盘CD,只要两年内按正常,只要两年内按正常的会员价格购买的会员价格购买5盘以上的盘以上的CD”; 会员按月收到促销商品广告和产品目录,从中选择商会员按月收到促销商品广告和产品目录,从中选择商品;客户也可以订购产品目录中的其他商品和特殊商品;客户也可以订购产品目录中的其他商品和特殊商品;品; 当会员履行了他们最初的订阅合同后,他们就具有了当会员履行了他们最初的订阅合同后,他们就具有了获得奖卷的资格,奖卷可以用来况换产品目录中的免获得奖卷的资格,奖卷可以
25、用来况换产品目录中的免费商品;费商品; 最近最近12个月内购买过商品的会员帐号为活动帐号,否个月内购买过商品的会员帐号为活动帐号,否则为非活动帐号;非活动帐号再次使用需先进行激活则为非活动帐号;非活动帐号再次使用需先进行激活。Copyright 2004 The McGraw-Hill Companies. All Rights reserved案例项目的初步范围:案例项目的初步范围:营销营销订阅订阅销售和订单录入(对所有的办事处)销售和订单录入(对所有的办事处)仓储(所有的发行中心)仓储(所有的发行中心)库存控制和采购库存控制和采购发货和验收(所有发行中心)发货和验收(所有发行中心)应收帐款
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