©2004 John MylopoulosCSC340Information Systems Analysis and DesignSystem Design -- 1XVII. System DesignXVII. System DesignWhat is System Design?The Outputs of System DesignThe (Global) System ArchitectureClassification of ApplicationsState of the Market©2004 John MylopoulosCSC340Information Systems Analysis and DesignSystem Design -- 2Major Tasks of System DesignMajor Tasks of System Design Identify major hardware and software subsystemsand components. Identify (usage, control or data) dependenciesamong subsystems. Decide on a hardware and software platform for thenew system. Design the information system software, database,and user interfaces.©2004 John MylopoulosCSC340Information Systems Analysis and DesignSystem Design -- 3Other Elements of System DesignOther Elements of System Design(...Not discussed in this course….) Plan control aspects of the application. Test plans. Code development standards. Priorities for design trade-offs. Implementation requirements (e.g., data conversion)©2004 John MylopoulosCSC340Information Systems Analysis and DesignSystem Design -- 4System ArchitectureSystem ArchitectureSystem refers to both hardware and software. The system architecture describes the collection ofinter-connected hardware nodes on which the softwarewill eventually run. A system architecture consists of: Hardware nodes, e.g., 486, 2MB RAM, 100MB diskOS: DOS Windows. The connectivity among nodes, e.g., length: <100ft,type: fiber optic, product: Novell 386 LAN, PC3270 The location of users, inputs and outputs;Key concern: Minimize data communicationKey concern: Minimize data communication©2004 John MylopoulosCSC340Information Systems Analysis and DesignSystem Design -- 5ExampleExample To each hardware node, associate users (actors)and network interconnectionsAccounts Receivable486, DOS Win100MB disk<200ft, Ethernet,Novell 386 LANBusiness Administrator1,500ft, Twistedpair SNAPurchasing Department486, DOS Win100MB disk486, DOS Win100MB disk<100ft, Twistedpair PC3270OS/400, 5 trm5GB diskIBM 3090, MVS25 terminalsFinancial ManagersVP Finance1mi fiber opt.TCP/IP<100mi, modem28800, PC3270Accounts Payable386 notepadsDOS 80MB disk486 DB serverDOS, 2GBdisk<100ft, Tokenring, Novell386©2004 John MylopoulosCSC340Information Systems Analysis and DesignSystem Design -- 6Distribution Issues:Distribution Issues:How Are Data Processed?How Are Data Processed?Batch modeBatch mode -- e.g., incoming/outgoing surface mail(purchase orders, invoices, cheques…On-line modeOn-line mode -- can save data entry time,particularly if end user can do the input, clearly theway of the future.Remote batchRemote batch -- data are input on-line on remotemachines, then fed in batch to centralizeddatabase.©2004 John MylopoulosCSC340Information Systems Analysis and DesignSystem Design -- 7New Technologies for I/O andNew Technologies for I/O andNew Standards for Data InterchangeNew Standards for Data InterchangeKeyless data entryKeyless data entry -- bar coding, optical characterrecognition, special keyboards.Pen inputPen input -- several products in the market.Electronic data interchange (EDI)Electronic data interchange (EDI) -- data aretransferred through telephone lines from one location toanother; e.g., credit card chargingImage and Document InterchangeImage and Document Interchange -- like electronicdata interchange, e.g., law enforcement, banking.HTML/XML/SGML -- markup languages for documents;SGML is a general markup languages for documents.©2004 John MylopoulosCSC340Information Systems Analysis and DesignSystem Design -- 8Choosing a System ArchitectureChoosing a System ArchitectureHere is a series of issues that need to be addressed: Establish batch and on-line computer processes; e.g.,on-site conference registration. Determine process cycles, i.e., when does each processneed to run, e.g., end-of-month, end-of-project. Establish processing locations -- identify user locations(and numbers). Distribute data to locations. Distribute software subsystems to locations. Assign technology -- what hardware, software is going torun where?©2004 John MylopoulosCSC340Information Systems Analysis and DesignSystem Design -- 9Classification of ApplicationsClassification of ApplicationsSpanTypeGroup/DeptEnterpriseInter-EnterpriseOperationalSupportE.g., regionalinventorycontrolE.g.,enterprise-wide cash mgtE.g., B2BEcommerceDecisionSupport(browsing+analysis)E.g., regionalmarketing infosystemE.g., corporatedatawarehouseE.g., DBs forcommunities ofinterestReal TimeE.g., videoconferencingwithin groupE.g., enterpr-wide video-conferenceE.g.,distributedmultimediaover theinternet©2004 John MylopoulosCSC340Information Systems Analysis and DesignSystem Design -- 10State of the MarketState of the MarketSpanTypeGroup/DeptEnterpriseInter-EnterpriseOperationalSupportPC, Windows,OLTP, OOproductsERPs, OLTPover privateintranetsEcommercetechnologiesDecisionSupport(browsing+analysis)COTS (mainlySQL-basedERPs, Web-basedproductsWeb-basedtechnologiesReal TimeMultimediatechnologymaturingERPs, Web-basedtechnologiesWeb-basedtechnologies•OLTP -- On-Line Transaction Processing•ERPs -- Enterprise Resource Planning systems•COTS -- Components Off-The Shelf©2004 John MylopoulosCSC340Information Systems Analysis and DesignSystem Design -- 11Data Management IssuesData Management Issues Identify amount and type of data persistence needed: Is simple file I/O sufficient? Is a Database Management System (DBMS) required? A DBMS is typically needed when: Data is accessed at a fine level of detail, Sophisticated indexing is required, There is a need to port data across multiple platforms, Data needs to be accessible from multiple platforms.Isolate persistence mechanisms fromIsolate persistence mechanisms
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