【正文】 4 導出現(xiàn)行系統(tǒng)的邏輯模型4 進行用戶需求分析與描述4 明確待建的目標4 導出待建的邏輯模型4 制定設計實施的初步計劃2023年 9月 28日 6時 52分4需求分析的任務就是借助于當需求分析的任務就是借助于當前系統(tǒng)的邏輯模型導出目標系前系統(tǒng)的邏輯模型導出目標系統(tǒng)的邏輯模型，解決目標系統(tǒng)統(tǒng)的邏輯模型，解決目標系統(tǒng)的的 “ 做什么做什么 ” 的問題。 初步確定新建的主要目標4 了解用戶實際的操作環(huán)境、操作過程和操作要求。請教專家2023年 9月 28日 6時 52分Existing systems analysis（現(xiàn)行系統(tǒng)分析)4Existing systems analysis（現(xiàn)行系統(tǒng)分析 )，有很多需求可能客戶與分析人員想都沒有想過，或者想得太幼稚。uMore accurate.uThere is no way that a question can be posed in response to an answer.(根據(jù)某一個回答再提問）2023年 9月 28日 6時 52分Forms analyses（表格分析）4To examine the various forms used by the client. Can lead to an accurate assessment of client’s needs. 4To find out exactly what is done and how.4Light on the flow of jobs.4附件 2：調研問卷4附件 3：廣州市農業(yè)信息系統(tǒng)用戶需求調查表.doc2023年 9月 28日 6時 52分4有些需求客戶講不清楚，分析人員又猜不透，這時就要請教行家。4類型：拋棄式原型和演化式原型2023年 9月 28日 6時 52分Throwaway Prototype4當我們遇到需求中的不確定性、二義性、不完整性或含糊性時，最有效的解決方法是建立 拋棄式 原型。4Scenarios (Use Cases) play an important role in objectoriented 演重要角色。t know We don39。u 形成文檔化的描述 問題和需求都需要形成文檔化的描述，使各種人員一致理解和認可。 2023年 9月 28日 6時 52分Type of Requirements4Bussiness requirementsuA system requirement (also called a business requirement) is a description of the needs and desires for an information system. A requirement may describe functions, features (attributes), and constraints.（系統(tǒng)需求是對信息系統(tǒng)的需求描述）4User requirementsu用戶使用產(chǎn)品必須要完成的任務（業(yè)務需求）2023年 9月 28日 6時 52分Type of Requirements4Functional requirements（功能需求）uA functional requirement is a function or feature that must be included in an information system to satisfy the business need and be acceptable to the users.（滿足系統(tǒng)需求的、被用戶認可的系統(tǒng)功能或者特征）uA functional requirement describes an interaction between the system and its environment..（系統(tǒng)與環(huán)境間的交互）2023年 9月 28日 6時 52分Type of Requirements4nonfunctional requirementsu A nonfunctional requirement is a description of the features, characteristics, and attributes of the system as well as any constraints that may limit the boundaries of the proposed solution.(限定范圍）u A nonfunctional requirement or a constraint describes a restriction on the system that limits our choices for constructing a solution to the problem.（限定選擇的解決方案）2023年 9月 28日 6時 52分Nonfunctional Requirements4Define system properties and constraints . reliability, response time and storage requirements. Constraints are I/O device capability, system representations系統(tǒng)表現(xiàn) , etc.4Process requirements may also be specified mandating要求 a particular CASE system, programming language or development method(過程要求）4Nonfunctional requirements may be more critical than functional requirements. If these are not met達到 , the system is useless2023年 9月 28日 6時 52分Nonfunctional RequirementsNonfunctionalRequirementsProductRequirementsOrganizationalRequirementsExternalRequirementsUsabilityRequirementsEfficiencyRequirementsReliabilityRequirementsPortabilityRequirementsDeliveryRequirementsImplementationRequirementsStandardsRequirementsInteroperabilityRequirementsEthicalRequirementsLegislativeRequirementsPerformanceRequirementsSpaceRequirementsPrivacyRequirementsSafetyRequirements法制2023年 9月 28日 6時 52分Level of Requirements業(yè)務需求項目視圖與范圍文檔用戶需求用例文檔質量屬性功能需求系統(tǒng)需求軟件需求規(guī)格說明其他非功能需求約束條件2023年 9月 28日 6時 52分Types of Requirements4The requirements definition and specification documents describe everything about how the system is to interact with its environment. Included are the following kinds of items.4Physical EnvironmentuWhere is the equipment to function?uIs there one location or several?uAre there any environmental restrictions, such as temperature溫度 , humidity濕度 , or magic interference磁干擾 ?2023年 9月 28日 6時 52分4InterfacesuIs the input ing from one or more other systems?uIs the output going to one or more other systems?uIs there a prescribed way in which the data must be formatted?uIs there a prescribed medium that the data must use?4Users and FactorsuWho will use the system?uWill there be several types of users?uWhat is the skill level of each type of user?uHow easy will it be for a user to understand and use the system?uHow difficult will it be for a user to misuse誤用 the system?Types of Requirements2023年 9月 28日 6時 52分4FunctionalityuWhat will the system do?uWhen will the system do it?uAre there several modes of operation?uHow and when can the system be changed or enhanced?uAre there constraints on execution speed, response time, or throughput?4DocumentationuHow much documentation is required?uShould it be online, in book format, or both?uTo what audience is each type of documentation addressed?Types of Requirements2023年 9月 28日 6時 52分4Datau For both input and output, what should the format of the data be?u How often will they be received or sent?u How accurate must they be?u To what degree of precision must the calculations be made?u How much data flow through the system?u Must any data be retained for any period of time?Types of Requirements2023年 9月 28日 6時 52分4ResourcesuWhat materials, personnel, or other resources are required to build, use, and maintain the system?uWhat skills must the developers have?uHow much physical space will be taken up by the system?uWhat are the requirements for power, heating, or air conditioning?uIs there a prescribed timetable for development?uIs there a limit on the amount of money to be spent on development or on hardware and software?Types of Requirements2023年 9月 28日 6時 52分4Securityu Must access to the system or to information be controlled?u How will one user’s data be isolated from others?u How will user programs be isolated from other programs and from the operating system?u How often will the system be backed up?u Must the backup copies be stored at a different location?