Today’s Agenda • System Architecture • Processing Methods • On-line, Batch • Centralized, De-centralized • Networking • LAN/WAN/MAN • Client/Server, File/Server
System Architecture • Refers to the Logical design and physical structure of a system • Includes hardware, software, design and processing methods • Environment & Platform • Server Farm with UNIX(s) + Apache • AS/400 with Websphere + NT partitions
Processing Methods • Environment and/or Platform refer to a specific combination of hardware and software • Influences system architecture • Reinforces bias (when all you’ve got is a hammer, everything looks like a nail) • Becomes religious (but there is no “one true” platform)
…just a few years ago • Two predominant environments • Mainframes with terminal access • Stand alone PC’s running one program at a time
Today • The Internet connects everything • Businesses are more dynamic than ever • Competitive pressure: e-commerce, 24/7 • Corporate “right sizing” • Mergers • Employees at all levels satisfy their own information needs – IT provides users with the technology, tools and resources • Requires that systems be cost effective, flexible and user-friendly
Impact on Analyst’s strategy • Business operational requirements • Match software to business process • Level of integration with outside systems • EDI, XML, information/transaction exchange • Level of access for customers and suppliers into your platform • Internet, telephony, call centers
On-line Data Processing • Transactions are processed completely when and where they occur • Users interact directly with the information system programs (not forms) • Programs update DB directly & immediately(input verification is critical to system integrity) • system availability is crucial • Consider cost of downtime, manual backup procedures
Batch Data Processing • Data is collected and processed in batches, logically and physically. • Data captured, then entered, then input. • May be more efficient than on-line • Typically used for large amounts of data that must be processed on a routine schedule • What in case study is batch?
Batch Data Processing • Transactions are collected and processed periodically • Computer operators can run batch programs on a pre-determined schedule without user involvement • Payroll, Accounting close off • Data Warehouse, EIS, DSS updates • EDI
Level of Automation • Volume: How much info is there? • Volatility: How often does info change? • Timeliness: When does matter? • Forms and batch processing • PDA & handheld data collection devices • With wireless modems • Online screens everywhere
Centralized Systems • Server or Host • Mainframe and terminals • e.g. IBM “big iron”, AS/400 and large UNIX • In the past, slow + $$$ communications networks limited remote data entry/input • Clustered systems • Many identical systems with load balancing, fail-over. e.g. Server farms. • A horror when it’s time to upgrade/update. • Heterogeneous environments • Variety of platforms, use middleware
Distributed Systems • For business, computing is distributed geographically, connected by networks • Local and regional tasks are performed by decentralized computers • Summary uploads to central office • May use Client/Server model
Distributed Systems Design • processing involves local and central data • Data may be stored closer to users and reduce network traffic • Easily scalable – new storage sites can be added without affecting network operation • Less likely to experience a catastrophic failure • …what about security? • …network management? • Database replication and synchronization issues
Distributed Processing Today • Distributed CPUs • SETI@Home • DistributedScience • Entropia • Distributed Storage (Peer-to-Peer) • Napster • Gnutella
Networks and the Net • The value of a network is the square of the number of things connected to it. — Metcalfe's law for Bob Metcalfe, the inventor of Ethernet and 3COM. • The value of the Net is the number of groups people on the network can form. Reid’s Law
The Net • Intranet, extranet, internet • Accessibility – browsers make presentation layer independent of the platform’s software/hardware/operating systems • Low cost communications • Widely implement standards (HTML, XML) • Security slowly getting better • Reliability – no guarantees yet • Throughput – last mile problem • Volatile standards and tools
Local Area Networks (LANs)/ Wide Area Networks (WANs) • LANs • Hardwire a group of PCs together in a limited area to a server • WANs • Uses a combination of phone lines, fiber optic cables, microwave transmission and satellites to connect PCs and LANs into a network that can span the globe • X25, Frame Relay, ATM (Asynch Xfer Mode) • Internet built on TCP/IP • MANs (Metropolitan Area Networks) • New Ethernet wireless standard
Network Issues • Software licensing • Traffic and Bandwidth • Security and Firewalls • Topology, Configuration, Protocol • These issues need an expert(I.e. your friends in CNS program)
Client/Server Systems • Divides processing between one or more clients and a central server • A client handles the user interface • Data entry • Editing • Data query • A server handles • Data access • Processing • Database management functions
Benefits of Client/Server • ? Easily scalable (up or down) to meet changing business needs ? • ? Transfer of expensive mainframe systems to less expensive clients ? • In practice, benefits are dubiousand many C/S projects failed • Is a browser on the Web closer to Client/Server or Mainframe/Terminal?
Systems Design Completion • System Design Specification • Created before the next SDLC Phase, Implementation • Detailed costs • Staffing • Scheduling • Oriented to Programmers so they know what to do • Oriented to Users so they know what they are getting
Approvals of the Systems Design Specification • Users approve all report and output screen designs, menu and data entry screens, source documents • IS Management will approve staffing, costs, hardware and software and effects on the operating environment • Other management – does the new system meet business objectives?
Technical and Management Presentations • Programmers/operators/IS staff • IS Management • Company management • Possible outcomes • Proceed with development • Perform additional work on the design phase • Terminate the project
Summary • Architecture • Processing • Networking • Completing the Design Phase of the SDLC