Today s Lecture. Software Architecture. Lecture 27: Introduction to Software Architecture. Introduction and Background of

Transcription

1 Today s Lectre Lectre 27: Introdction to Software Architectre Kenneth M. Anderson Fondations of Software Engineering CSCI Spring Semester, 1999 Introdction and Backgrond of Software Architectre concepts styles domains Lectre 27 1 Lectre 27 2 Software Architectre The principled stdy of software components, inclding their properties, relationships, and patterns of combination Also, a particlar set of software components as combined in a particlar software system Lectre 27 3

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3 Pipe and Filter Pipe and Filter Pipe and Filter Layered Abstract Machines Layered Abstract Machines Bs

4 The Role of Architectre Pipe and Filter Shared Repository Layered Abstract Machines Bs Architectre Reqirements Bsiness Lectre The Role of Architectre The Role of Architectre Architectre Architectre Reqirements Reqirements Problem definition, rationale, and financial plan Bsiness System featres, fnctions, and sage scenarios Bsiness System featres, fnctions, and sage scenarios Lectre Lectre 27 16

5 The Role of Architectre The Role of Architectre By/bild strategy for each component Architectre Major components and interfaces Architectre Major components and interfaces Reqirements Problem definition, rationale, and financial plan Reqirements Problem definition, rationale, and financial plan Bsiness System featres, fnctions, and sage scenarios Bsiness System featres, fnctions, and sage scenarios Lectre Lectre The Role of Architectre The Role of Architectre Internal decomposition, fnctions, and data strctres Internal decomposition, fnctions, and data strctres By/bild strategy for each component By/bild strategy for each component Architectre Major components and interfaces Architectre Major components and interfaces Reqirements Problem definition, rationale, and financial plan Reqirements Problem definition, rationale, and financial plan Bsiness System featres, fnctions, and sage scenarios Bsiness System featres, fnctions, and sage scenarios Lectre Lectre 27 20

6 The Central Planning Phase The Central Planning Phase Planning Phases Architectre Architectre Reqirements Reqirements Bsiness Lectre Bsiness Lectre Good Architectre Lowers Cost Addresses Integration Isses Cost of Error Repair Bsiness Planning Phases Reqirements Architectre Error Cont System Test Errors Integration Test Errors Unit Test Errors Phase of Error Discovery Lectre Lectre 27 23

7 Addresses Integration Isses Error Cont Programming Langages Unit Test Errors System Test Errors Integration Test Errors Lectre Addresses Integration Isses Error Cont Architectre Technology Programming Langages Unit Test Errors System Test Errors Integration Test Errors Lectre Architectral Domains Architectral Domains Compter Science Domain Bs Pipes and Filters Layered Abstract Machines Shared Repository Clients and Servers Lectre Compter Science Domain Bs Pipes and Filters Layered Abstract Machines Shared Repository Clients and Servers Lectre 27 28

8 Architectral Domains Translation Data Processing Transaction Processing Telephone Call Processing Flight Dynamics Control Problems Soltions Compter Science Domain Bs Pipes and Filters Layered Abstract Machines Shared Repository Clients and Servers Lectre Compter Science Domain Lectre Problems Soltions A program is compiled by sccessive application of lexical analysis, syntactic analysis, semantic analysis, and code generation. Problems Soltions A program is compiled by sccessive application of lexical analysis, syntactic analysis, semantic analysis, and code generation. Compter Science Domain Compter Science Domain The otpt of one component is the inpt to another component. Lectre Lectre 27 32

9 Problems Soltions Problems Soltions Each agent in the telephone network is a separate comptational entity. Compter Science Domain Compter Science Domain Lectre Lectre Problems Soltions Each agent in the telephone network is a separate comptational entity. Problems Soltions Compter Science Domain Each operating system process is a separate comptational entity. Compter Science Domain Lectre Lectre 27 36

10 Problems Soltions Network services are organized as layers, where each layer adds vale to services of lower layers. Services at a layer are defined independently of how they are performed. Problems Soltions Network services are organized as layers, where each layer adds vale to services of lower layers. Services at a layer are defined independently of how they are performed. Compter Science Domain Lectre Compter Science Domain Components are organized as layers, sch that each layer provides services only to next higher layer and ses services only of next lower layer. Lectre Architectral Style Generic set of components and arrangement of those components Constraint on components and their interconnections Often given a name...convenient for qickly conveying essential information Example: DBMS Architectre Traditional Bsiness Data Processing Processing steps are independent programs Each rns to completion before next step starts Data stored and passed throgh magnetic tapes Validate Sort Update Report Lectre Lectre 27 40

11 Example: DBMS Architectre Traditional Bsiness Data Processing Processing steps are independent programs Each rns to completion before next step starts Data stored and passed throgh magnetic tapes Validate Sort Update Report Example: DBMS Architectre Centralized Database Monolithic qery/pdate/store engine Applications as serializable transactions T2 T1 T3 Database Batch Seqential Architectre Lectre Lectre Example: DBMS Architectre Centralized Database Monolithic qery/pdate/store engine Applications as serializable transactions Example: DBMS Architectre Modern Database Toolkits Discrete, interchangeable components Applications as distribted clients T1 T2 T3 Server Interface Database Transaction Manager Qery Processor Bffer Manager Storage Manager Shared Repository Architectre Lectre Lectre 27 44

12 Example: DBMS Architectre Modern Database Toolkits Discrete, interchangeable components Applications as distribted clients Integration of mltiple databases Transaction Manager Server Interface Qery Processor Storage Manager Bffer Manager Analogy: Chemical Engineering Chemical engineering evolved from a mixtre of craft, mysticism, wrong theories, and empirical gessesé Improvements were very slow ntil the Scientific RevoltionÉOnly then were mystical interpretations replaced by scientific theories: thogh the early theories were often wrong, theyéplayed a leading role in stimlating thoght. - J.T. Davies Lectre Lectre Analogy: Chemical Engineering Interesting Architectral Points Theory ignored by engineers Hacking worked ntil problems with scale Scale problems solved by development of relatively small nmber of nit operations Strong emphasis on relationship to process Handbook of chemical engineering eventally developed and sed Unit Operations of Chemical Engineering Distillation Evaporation Drying Filtration Absorption Extraction Lectre Lectre 27 48

13 Unit Operations of Software Engineering Inpt Validation Stats Monitoring Load Balancing Translation Filtering Mlticasting Lectre Analogy: Compter Engineering Interesting Architectral Points Relatively small nmber of component kinds Properties constrained by physical laws Scale by replicating components Compared to Software Architectre Very large nmber of component kinds Constraints hard to determine Scale by adding new component kinds Lectre Analogy: Civil Engineering Architectral Styles Colonial, Victorian, Ranch, etc. Bilding Codes Electrical, strctral, zoning, etc. Special Expertise Slate roofs, post and beam, logs, etc. Analogy: Civil Engineering Architectral Styles Colonial, Victorian, Ranch, etc. ç Pipes and filters, layers, client/server, etc. Bilding Codes Electrical, strctral, zoning, etc. Special Expertise Slate roofs, post and beam, logs, etc. Lectre Lectre 27 52

14 Analogy: Civil Engineering Architectral Styles Colonial, Victorian, Ranch, etc. ç Pipes and filters, layers, client/server, etc. Bilding Codes Electrical, strctral, zoning, etc. ç Formal specifications Special Expertise Slate roofs, post and beam, logs, etc. Analogy: Civil Engineering Architectral Styles Colonial, Victorian, Ranch, etc. ç Pipes and filters, layers, client/server, etc. Bilding Codes Electrical, strctral, zoning, etc. ç Formal specifications Special Expertise Slate roofs, post and beam, logs, etc. ç Domain-specific architectres Lectre Lectre 27 54