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1、软件体系结构 信息共享体系结构 Shared Information孙志岗*1 Where are we?Date2 Families of Architectural StylesDate3 Families of Architectural StylesDate4 Families of Architectural StylesDate5 Families of Architectural StylesDate6 Shared Information SystemsnStyle represents a large variety of systems 这种风格描绘很多种系统many va
2、riants depending on nature of shared data 共同特点是共享数据nStyle addresses mechanisms for: 风格说明其运行机制是collecting, manipulating and preserving large bodies of data 收集、操作、保存大量的数据nDatabases are a natural example, but not the only one 数据库是一个典型的例子，但不是仅有的例子well see others in this lectureDate7 Shared Information S
3、ystemsnHigh level viewwhat are the apparent features of this style? 风格的明显特点是什么？what are some issues regarding this style? 这种这个风格有什么可研究的问题？Date8 Shared Information SystemsnAdvantageseasy to add consumers and producers of data 很容易增加数据的生产者和消费者nHow about modifier?nIssuessynchronization（同步）configuration
4、and schema management（配置 和管理） atomicity（原子性）consistency（一致性）persistence（持久性）performance（性能）Date9 Shared Information Systems LineagenEarliest repositories appear in batch sequential systems 早期的仓库出现在批处理系统mainframes, drums, magnetic tapes, disc drivesresources manually managed 人工调配资源nPressure for on-li
5、ne access to data 迫切需要数据即时存取requirement to make access to data easy and instant 简捷地数据存取help to drive the shift from batch-sequential to interactive processing 促进了从批处理到交互式处理的转变Date10 Shared Information Systems LineagenTodayshared information systems appear everywhere from the smallest business, to th
6、e most advanced scientific applications 从最小的商业应用到最顶尖的科学应用，信息共享无 处不在many applications provide access mechanisms to shared data 很多应用提供对共享数据的存取机制the Web has become a giant distributed repository Web成为庞大的分布式仓库Date11 Evolution of Shared Information SystemsnBatch Sequential Systemsflat file access (I/O)Da
7、te12 Early File AccessnIn the earliest systems, code had to be written to position the media, read the data, and do any associated “house cleaning” operations. 早期的系统，很难编写代码来完成定位存储介质、读数据等 操作Date13 Early File AccessnAdvances in OS development focused on the abstraction of devicesthe demand to use exte
8、rnal data helped to drive the development of more capable file systemsnflat file systems - one level of directories that contain only filesnhierarchical file systems - directories that can contain files and more directoriesnlanguage and OS support for many file types and file access methodsDate14 Ev
9、olution of Shared Information SystemsnDatapool (Shared Memory) Example:Enabled by availability of RAM and languages to permit the sharing of common data (E.g., FORTRAN COMMON BLOCK)Processes are not necessarily sequentialGets messy without implementation rules - what are the issues?Date15 Repository
10、 ArchitectureDate16 Unified Schemas for Integrating DatabasesAbstraction: multiplex the databases; put filters on the query/update to match diverse views 抽象： 复合多个数据库； 在查询/更新操作中 增加过滤器来匹配 不同的视图Date17 Multi-databasesDate18 Evolving Database ArchitecturesnBatch processing: Standalone programs （独立的程序）res
11、ults were passed from one to another on magtape （结果通过磁带从一个程序传到另一个程序）batch sequential model （批处理风格）nInteractive processing: concurrent operation and faster updates preclude batching, so updates are out of synch with reports. 并行操作、更快的更新速度，但是使更新和报告难以保持同步。Repository model with external control （仓库风格）Pro
12、blem: information became distributed Problem: information became distributed among many different among many different DBsDBs. . 新问题：信息分布到很多不同的数据库新问题：信息分布到很多不同的数据库Date19 Evolving Database ArchitecturesnUnified schemas:create one virtual database by defining (passive) consistent conversion mappings t
13、o multiple DBs 建立一个虚拟数据库，定义到多个数据库的静态映射nMulti-database: DBs have many users; passive mappings dont suffice; use active agents. 数据库有很多用户；静态映射不满足要求；使用活动 的代理。 “Layered” hierarchy 层次风格Date20 Computer Aided Software EngineeringnInitially just translation from source to object code: compiler, library, link
14、er, make 起初，就是做从源代码到目标代码的转换nGrew to include design record, documentation, analysis, configuration control, incrementality 开始包含分析、设计、调试、测试、文档、配置管理、增量 编译等功能nIntegration demanded for 20 years, but not here yet. 集成已经作了20年，但还没有结束Date21 CASE vs. DBMSnAs compared to databases, CASE has:more types of data 更
15、多的数据类型fewer instances of each type 更少的数据类型实例slower query rates 更慢的查询频率larger, more complex, less discrete information 更大，更复杂，更集中的信息but not shorter lifetime 生命周期没有更短Date22 Traditional CompilerDate23 Example: Modern Canonical CompilerDate24 Canonical CompilerDate25 Software Tools with Shared RepresentationDate26 Evolution
