软件体系结构VIP

1、软件体系结构体系结构评审Architectural Reviews,孙志岗 ,Architectural Reviews,Architectural reviews are a key step in architecture-based development. They include a method (such as SAAM or ATAM), but the full practice includes more than that.体系结构评审是开发过程中的一个重要环节。有专门的评审方法(SAAM、ATAM)，但在实践中并不仅仅是这些 We will discuss cost/b

2、enefits of architectural reviews different architectural review techniques preconditions for an architectural review architectural review activities outputs from an architectural review,Costs of Architectural Reviews,There are three different types of costs of holding regular architectural reviews.

3、direct staff costs直接员工开销 organizational overhead组织管理开销 indirect staff costs间接员工开销,Examples of Direct Staff Costs,AT each has a different cost and provides different information.有很多种评审技术。每种需要不同的开销，提供不同的信息 These techniques fall into one of two categories. questioning techniques: applied to evaluate an

4、y aspect of an architecture for any given reason提问技术：用来评价体系结构的任何方面 measuring techniques: applied to answer questions about a specific quality度量技术：回答关于某项质量的问题,Questioning Techniques,Scenario-based techniques describes a specific interaction between stakeholders and a system描述角色与系统交互的过程 example: SAAM,

5、 ATAM (partially) Questionnaire-based techniques（基于问卷的技术） Some questions apply to all architectures (especially those in a single domain).有些问题被用于所有的体系结构，尤其是在单一领域内 Some questions ask about details of a specific architecture.有些问题询问一个特定结构的细节 Some ask about the development process. “Is there a single ar

6、chitect?” “How do you ensure conformance?”“你们怎样保证一致性,Questioning Techniques,Questionnaires are reused; they reflect more maturity or experience within a domain.问卷可以重用；它们体现了在一个领域内的成熟度和经验是否丰富 Scenarios must be developed anew for each system.场景必须为每个系统重新开发,Measuring Techniques,Metrics: quantitative inte

7、rpretations of observable measures量度：可测质量的定量说明 complexity metrics identify areas where modifications may be difficult复杂度的测量指明在哪个区域修改会很困难 performance metrics suggest areas where bottlenecks may occur性能的测量提示瓶颈会在哪里发生 Reviews tend to focus on results of metrics度量的结果 assumptions underlying the interpreta

8、tion of the metrics (e.g., assumed event distribution)对度量的解释中的潜在假定,Measuring Techniques,Simulations, prototypes, experiments: domain specific models of an architecture or performance model仿真、原型、实验：建立体系模型或者性能模型 are expensive to create often exist as part of development anyway May answer issues raised

9、 by questioning technique 可以回答提问技术提出的问题 “What evidence do you have that performance is adequate?”“你凭什么说可以达到这个性能,Properties of Review Techniques,Review Process,An architectural review has three major elements. preconditions: the set of necessary assets and conditions that must be in place before a re

10、view can be performed successfully前提：评审成功进行之前，必要的资源和条件必须到位 activities of the review itself活动：评审本身 outputs: the report of review results输出：评审结果报告,Review Preconditions,Understand the context of the review理解评审的上下文 Assemble the right people集合正确的人 Set organizational expectations and support期望和支持 Prepare

11、for review为评审做准备 Obtain representation of the architecture获得体系结构文档,Preconditions: Context,Planned review part of normal development activity正常开发活动的一部分 non-adversarial（非敌对性的） scheduled well in advance（事先安排好日程） built into projects schedule and budget包含在项目日程和预算之内 Unplanned usually occurs when project i

12、s in trouble通常在项目出现问题时采用 often devolves into finger-pointing导致互相责备 can be painful for project already struggling对于已经苦苦挣扎了很久的项目而言，有些痛苦,Preconditions: Context,Timing of the review early “architecture discovery review” is done after requirements are set, but before the architecture is firm需求分析之后，体系结构还没

13、有确定之前进行 is used to understand implications of requirements on architecture用来理解需求在体系结构方面的隐含内容 checks for requirements feasibility（检查需求的可行性） prioritizes architectural goals（为质量目标排序） full architectural review is done when architectural documentation is available体系结构文档可用时进行 is used to evaluate qualities

14、 of proposed architecture评价被评体系结构的质量,Preconditions: People,Representatives of project（项目代表） architect designers of major modules stakeholders representatives Review team members (ideally, a separate unit)评审团成员(理想情况下是一个独立组织) at least one domain expert included至少有一个领域专家 someone to handle logistics (e.

15、g., meeting rooms, supplies)后勤人员(会议室、茶水、食品) librarian to organize documentation文档管理员 “apprentice reviewer” for growth成长中的评审员学徒,Preconditions: Review Team,The review team must be assembled so that members are perceived as impartial, objective, and respected成员要公正、客观和被尊重 members devote their full-time

16、effort to the review成员全心加入评审 members are fluent in architecture and architectural issues成员要训练有素而且口才好 it is located close to artifacts being examined有足够的权限检查被评审材料,Preconditions: Review Team,The team must have access to applicable domain knowledge (perhaps via consultants to the team)适当的领域知识 design do

17、cuments设计文档 review criteria评审标准 support staff支持人员,Preconditions: OrganizationalExpectations,A contract between the review team and the sponsor of the review must be established. Who will be told what upon completion?结束后，哪些内容可以被告诉哪些人 What will (not) be the review criteria?什么是(不是)评审标准？ What/who will b

18、e made available to team?哪些人和物是评审团可以使用的？ What follow-up is expected?希望评审的结果如何？ How long will the review take?要评审多久,Preconditions: OrganizationalExpectations,Organizational culture and support must be considered. Are reviews part of the standard project life cycle?评审是项目的基本生命周期的一部分吗？ Is serving on a r

19、eview team considered good for ones career?为评审团服务是份好差事吗？ Will the organization allow its superior designers time off from their projects to serve on review teams?企业允许它的高级设计师把他的项目放在一边来参加评审吗？ Is there a standing review organization (even though members may rotate on and off)?有常设的评审组织吗(即便成员常进进出出),Preco

20、nditions: Read-Ahead Material,For project being reviewed questionnaires scenarios (These are created as part of the review, but time should be allowed for project members to digest the information.) For review team description of architecture rationale for architecture Ideally, material will address

21、 the review questions. (Passing this test because the questions were known in advance is not cheating, but good engineering!)理想情况，材料要能说明评审时的问题,Preconditions: Ranked Qualityand Behavioral Requirements,Plan to examine three to five quality and behavioral requirements.计划检查3到5个质量和行为需求 A particular repre

22、sentation medium (language) for the architecture is not necessary. As long as the information can be extracted (using project members as necessary), the form of the representation is not important.一个专门的体系结构表述媒体(语言)目前并不是必须的。由项目成员来讲解信息，表述的形式并不重要,Review Activities,Evaluate “Run” the scenarios and ask t

23、he questions, or answer the items in the checklist.按场景执行，并询问相关问题；或者回答问卷里的问题 Perform the experiments.（演示实验） Execute the prototypes or simulations.运行原型或仿真程序 Record critical issues highlighted in the review评审中发现的严重问题 comments of project members on these issues项目成员对这些问题的说明,Review Activities,Rank the iss

24、ues project-threatening（生死攸关） major minor Each issue raised should be addressed in terms of changing the architecture relaxing the requirements,Review Activities,Warning signs architecture forced to match organization组织模式影响体系结构 top-level components number over 25顶层组件数超过25个 one requirement drives ent

25、ire design一项需求决定整个设计 architecture depends on alternatives in the operating system体系受操作系统选择的影响,Review Activities,Warning signs choice of software components is dictated by hardware personnel由硬件人员选择软件组件 redundancy not needed for reliability面对可靠性时，不考虑冗余手段 design is exception driven零散的小的事件影响设计 no identi

26、fiable architect没有确定的架构师,Output from Review,Set of ranked issues supporting data contained in formal report feedback to project Enhanced system documentation增强的系统文档 Set of scenarios for future use将来会用到的场景集 Identification of potentially reusable components认定潜在的可重用组件 Estimation of costs and benefits估算

27、成本和收益,SAAM: Software Architecture Analysis Method 一种简单的基于场景的评审技术,Qualities Are Too Vague for Analysis,Is the following system modifiable?这个系统具有适应性吗？ Background color of the user interface is changed merely by modifying a resource file.通过修改资源文件，可以改变界面的背景色 Dozens of components must be changed to accom

28、modate a new data file format.必须修改许多组件才能适应新的文件格式 A reasonable answer is一个合理的答案： yes with respect to changing background color有，从改变背景色的角度来看 no with respect to changing file format没有，从改变文件格式的角度来看,Qualities Are Too Vague for Analysis,Qualities only have meaning within a context.质量因素只在一定的上下文里才有意义 SAAM s

29、pecifies context through scenarios.SAAM通过场景指定上下文,Scenarios,A scenario is a brief description of a stakeholders interaction with a system.场景就是一个角色与系统交互过程的简单描述 When creating scenarios, it is important to consider all stakeholders.建立场景的时候，一定要考虑到所有的角色 Customer、User、Developer、Maintainer、Attacker The scen

30、arios that are of most interest in a SAAM evaluation are change scenarios.SAAM最关心的是变化场景,Steps of a SAAM Evaluation,Identify and assemble stakeholders确认和召集角色 Develop and prioritize scenarios制定场景，并排好优先级 Describe candidate architecture(s)描述候选的体系结构 Classify scenarios as direct or indirect把场景分类为直接场景和间接场景

31、 Perform scenario evaluation进行场景评估 Reveal scenario interactions展现场景间的相互影响 Generate overall evaluation整体评估,Step 1: Identify and Assemble Stakeholders,Step 1: Identify and Assemble Stakeholders,Step 1: Identify and AssembleStakeholders,Step 2: Stakeholders Develop andPrioritize Scenarios,Scenarios sho

32、uld be typical of the kinds of evolution that the system must support:场景应该是系统必须支持的各种演化的典型： functionality development activities change activities Scenarios should represent tasks relevant to all stakeholders.所有角色都应该能在场景中体现出来 Rule of thumb: 10-15 prioritized scenarios应该有10-15个优先的场景,Step 3: Describe C

33、andidateArchitectures,It is frequently necessary to elicit appropriate architectural descriptions.通常，对体系结构进行适当的描述是非常重要的 Structures chosen to describe the architecture will depend on the type of qualities to be evaluated.以我们需要的质量为依据，选择用来描述体系结构的结构,Step 4: Classify Scenarios,There are two classes of sc

34、enarios. Direct scenarios are those that can be executed by the system without modification.直接场景是那些不需要修改系统就能执行的场景 Indirect scenarios are those that require modifications to the system.间接场景是那些需要修改系统的场景 The classification depends upon both the scenario and the architecture.场景的类型因系统而异 For indirect scenarios we gauge the order of difficulty of each change: e.g. a person-day, person-week, person-month, person-year.对间接场景，我们要度量适应每个变化的难度（工作量,Step 5: Perform Scenario Evaluation,For each indirect scenario identify the components, data