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1、軟 件 體 系 結(jié) 構(gòu)信 息 共 享 體 系 結(jié) 構(gòu)Shared Information孫 志 崗 22021-4-27 Where are we? 32021-4-27 Families of Architectural Styles 42021-4-27 Families of Architectural Styles 52021-4-27 Families of Architectural Styles 62021-4-27 Families of Architectural Styles 72021-4-27 Shared Information Systemsn Styl
2、e represents a large variety of systems這種風格描繪很多種系統(tǒng) many variants depending on nature of shared data共同特點是共享數(shù)據(jù)n Style addresses mechanisms for:風格說明其運行機制是 collecting, manipulating and preserving large bodies of data收集、操作、保存大量的數(shù)據(jù)n Databases are a natural example, but not the only one數(shù)據(jù)庫是一個典型的例子，但不是僅有的例子
3、 well see others in this lecture 82021-4-27 Shared Information Systemsn High level view what are the apparent features of this style?風格的明顯特點是什么？ what are some issues regarding this style?這種這個風格有什么可研究的問題？ 92021-4-27 Shared Information Systemsn Advantageseasy to add consumers and producers of data很容
4、易增加數(shù)據(jù)的生產(chǎn)者和消費者n How about modifier?n Issuessynchronization（同步）configuration and schema management（配置和管理）atomicity（原子性）consistency（一致性）persistence（持久性） performance（性能） 102021-4-27 Shared Information Systems Lineagen Earliest repositories appear in batch sequential systems早期的倉庫出現(xiàn)在批處理系統(tǒng) mainframes, dru
5、ms, magnetic tapes, disc drives resources manually managed人工調(diào)配資源n Pressure for on-line access to data迫切需要數(shù)據(jù)即時存取 requirement to make access to data easy and instant簡捷地數(shù)據(jù)存取 help to drive the shift from batch-sequential to interactive processing 促進了從批處理到交互式處理的轉(zhuǎn)變 112021-4-27 Shared Information Systems
6、Lineagen Todayshared information systems appear everywhere from the smallest business, to the most advanced scientific applications從最小的商業(yè)應用到最頂尖的科學應用，信息共享無處不在many applications provide access mechanisms to shared data很多應用提供對共享數(shù)據(jù)的存取機制the Web has become a giant distributed repositoryWeb成為龐大的分布式倉庫 12202
7、1-4-27 Evolution of Shared Information Systemsn Batch Sequential Systemsflat file access (I/O) 132021-4-27 Early File Accessn In the earliest systems, code had to be written to position the media, read the data, and do any associated “house cleaning” operations.早期的系統(tǒng)，很難編寫代碼來完成定位存儲介質(zhì)、讀數(shù)據(jù)等操作 142021-
8、4-27 Early File Accessn Advances in OS development focused on the abstraction of devices the demand to use external data helped to drive the development of more capable file systemsn flat file systems - one level of directories that contain only filesn hierarchical file systems - directories that ca
9、n contain files and more directories n language and OS support for many file types and file access methods 152021-4-27 Evolution of Shared Information Systemsn Datapool (Shared Memory) Example: Enabled by availability of RAM and languages to permit the sharing of common data (E.g., FORTRAN COMMON B
10、LOCK) Processes are not necessarily sequential Gets messy without implementation rules - what are the issues? 162021-4-27 Repository Architecture 172021-4-27 Unified Schemas for IntegratingDatabasesAbstraction:multiplex the databases; putfilters on the query/update tomatch diverse views抽象：復合多個數(shù)據(jù)庫；
11、在查詢/更新操作中增加過濾器來匹配不同的視圖 182021-4-27 Multi-databases 192021-4-27 Evolving Database Architecturesn Batch processing: Standalone programs （獨立的程序） results were passed from one to another on magtape （結(jié)果通過磁帶從一個程序傳到另一個程序） batch sequential model （批處理風格）n Interactive processing: concurrent operation and fas
12、ter updates preclude batching, so updates are out of synch with reports. 并行操作、更快的更新速度，但是使更新和報告難以保持同步。 Repository model with external control （倉庫風格） 202021-4-27 Evolving Database Architecturesn Unified schemas:create one virtual database by defining (passive) consistent conversion mappings to multip
13、le DBs建立一個虛擬數(shù)據(jù)庫，定義到多個數(shù)據(jù)庫的靜態(tài)映射n Multi-database: DBs have many users; passive mappings dont suffice; use active agents. 數(shù)據(jù)庫有很多用戶；靜態(tài)映射不滿足要求；使用活動的代理。 “Layered” hierarchy層次風格 212021-4-27 Computer Aided SoftwareEngineeringn Initially just translation from source to object code: compiler, library, linker,
14、 make起初，就是做從源代碼到目標代碼的轉(zhuǎn)換n Grew to include design record, documentation, analysis, configuration control, incrementality開始包含分析、設計、調(diào)試、測試、文檔、配置管理、增量編譯等功能 n Integration demanded for 20 years, but not here yet.集成已經(jīng)作了20年，但還沒有結(jié)束 222021-4-27 CASE vs. DBMSn As compared to databases, CASE has:more types of da
15、ta更多的數(shù)據(jù)類型fewer instances of each type更少的數(shù)據(jù)類型實例slower query rates 更慢的查詢頻率larger, more complex, less discrete information更大，更復雜，更集中的信息 but not shorter lifetime生命周期沒有更短 232021-4-27 Traditional Compiler 242021-4-27 Example: Modern CanonicalCompiler 252021-4-27 Canonical Compiler 262021-4-27 Software
16、 Tools with SharedRepresentation 272021-4-27 Evolution of CASE EnvironmentsEvolution is much like databases:n Interaction: batch - interactive交互：批處理交互式n Granularity: complete processing -incremental粒度：完全處理增量n Coverage: compilation - full life cycle覆蓋：編譯全生命周期n Like databases, started with batch sequ
17、ential style從批處理風格開始n Integration needs led to repositories with rigid control, then to open systems in layers對集成性的要求，促成了倉庫風格被應用，讓系統(tǒng)開始分層 282021-4-27 Varieties of RepositoriesDiscriminate on control strategy（在控制策略上的區(qū)別）n Predetermined by designer （設計者預先定義好） Compilersn Driven by types of information i
18、n input stream 輸入流的信息類型決定 Database transaction systemn Driven by availability of new information from other parts of the system （系統(tǒng)其他部分的新信息決定） Scratchboard （刮板）n Opportunistic: driven by state of computation機會主義：計算的狀態(tài)決定 Blackboard 292021-4-27 Repository (Blackboard) 302021-4-27 The Blackboard Mode
19、ln Knowledge Sources Problem-appropriate knowledge partitioned into separate, independent computations把問題分成幾個部分，每個部分獨立計算 React to changes in blackboard響應黑板上的變化n Blackboard Data Structure Global database containing entire state of problem solution全局數(shù)據(jù)庫包含解域的全部狀態(tài) Only means by which knowledge sources i
20、nteract知識源互相作用的唯一媒介n Control Knowledge sources respond “opportunistically”讓知識源響應偶然事件 312021-4-27 The Blackboard Model 322021-4-27 Blackboard Architecturen Key ideas knowledge shared and distributed among some number of cooperating processes知識在一些協(xié)作的processes之間共享和分布 opportunistic processing of data機
21、會主義地處理數(shù)據(jù)n The Blackboard Architecture have 3 major components knowledge sources （知識源） blackboard （黑板） control （控制）n Historical examples: Hearsay I, Hearsay II, HASP/SAIP, CRYSALIS, ATOME Originally most were from signal processing/interpretation domains （信號處理、專家系統(tǒng)、模式識別領域經(jīng)常采用） 332021-4-27 Blackboard
22、 Architecture 342021-4-27 Blackboard Problem Characteristicsn no direct algorithmic solution沒有直接的算法可解 multiple approaches to solving the problem多種方法都可能解決問題 various domain expertise required to solve the problem需要多個領域的專門知識協(xié)作解決n uncertainty error and variability in data and solution數(shù)據(jù)和解決方法可能錯誤或變化 mod
23、erate to low “signal-to-noise-ratio” in data數(shù)據(jù)中信噪比的變化 Uncertainty interferes with algorithmic solutions算法接口的變化 352021-4-27 Blackboard Problem Characteristicsn “Best-effort” or approximation is good enoughno single discrete answer to problem, or “right” answer may vary問題沒有唯一的解答，或者“正確”答案會變化n examples
24、signal processing （信號處理）problem solving (planning, logistics, diagnostics) compiler optimization 362021-4-27 Knowledge Sourcesn Objective: contribute knowledge that leads to solution提供解決問題的知識n Representation: procedures, sets of rules, logic assertions過程、規(guī)則、邏輯斷言n Action: modify only the blackboard
25、(or control data - magic)只修改黑板n Responsibility: know when its possible to help知道何時能發(fā)揮作用n Selection: loosely-coupled subtasks, or areas of specialization低耦合的子任務，或者有特別的能力 372021-4-27 Blackboard Data Structuren Objective: hold data for use by knowledge sources保存知識源要使用的數(shù)據(jù)n Representation: stores object
26、s from solution space, including保存來自解空間的數(shù)據(jù)，包括 n input data, partial solutions, alternatives, final solutions, control datan objects and properties define the terms of the discoursen relationships are denoted by named links (“next-to”, “part-of”)n Organization: hierarchical, possibly multiple hierarc
27、hies; links between objects on same or different levels分層；鏈接同層或不同層的對象 382021-4-27 Controln Objective:make knowledge sources respond opportunistically讓知識源響應偶然事件n Representation:keeps various sorts of information about which knowledge sources could operate and picks a sequence that allows the solutio
28、n process to proceed a step at a time了解各個知識源的能力，決策解決問題的步驟n Remark: the control mechanisms are thoroughly ad hoc控制機制是徹底的與時俱進 392021-4-27 Example：The Puzzle Metaphor 402021-4-27 Example：The Puzzle Metaphorn Data within the blackboard is often structured hierarchicallyLevel 4 assemble chunksLevel 3 b
29、uild chunks of edges build chunks of skyLevel 2 collect edge piecescollect sky piecesLevel 1 Turn all pieces picture side up 412021-4-27 Hearsay IIn Complex blackboard system to deal with arbitrary speech recongition (a difficult problem):Ambiguity in segmentation（音節(jié)分割問題）: “Marys truck” versus “Mar
30、y struck” Ambiguity in stress（重音問題）: “disease” versus “dizzies”Ambiguity in grammar（語法問題）: “The horse raced past the barn fell” Ambiguity in semantics（語義問題）: “I saw the man on the hill with the binoculars” 422021-4-27 Problem Solving Strategyn Had to be incremental, opportunistic, flexible必須是增量的、機會
31、的、靈活的n Hearsay-II employed several strategies: Bottom-up (synthetic) Top-down (analytic) General hypothesize-and-test （猜測和測試）n Blackboard structure entertained many simultaneous hypotheses黑板結(jié)構(gòu)可以同時處理多種假設n Control was complex: had a monitor portion and a priority based scheduler控制很復雜：有一個監(jiān)視器，采用基于優(yōu)先級的調(diào)度
32、 432021-4-27 Hearsay II Structure 442021-4-27 Lecture Summaryn Repositories are ubiquitous in computer-based applications.倉庫在計算機應用中幾乎無處不在n Shared information systems in many areas show similar trends, stimulated by similar technological and business pressures.信息共享系統(tǒng)在很多領域有相似的發(fā)展趨勢，因為有相似的技術和商業(yè)壓力的激勵n Blackboards are specialized types of repositories for dealing with “messy” information processing domains where the control strategy must be opportunistic.黑板是一種特別的倉庫，主要用于需要對凌亂的信息進行處理的領域，其控制策略必須是機會主義的
軟件體系結(jié)構(gòu)信息共享體系結(jié)構(gòu)SharedInforma
