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York University
Information Technology
ITEC 3010

Systems Analysis and Design I ITEC3010 – Fall 2010 – Luiz Cysneiros Lecture 8 – Environments, Alternatives and Decisions – Nov 9 Major Activities in the Analysis Phase - Gather information - Define system requirements - Prototype for feasibility and discover - Prioritize requirements - Generate and evaluate alternatives - Review recommendations with management The End of the Analysis Phase - During analysis many more requirements may be determined than can be dealt with - Must prioritize and evaluate them - Several alternative packages of requirements may be developed - A committee of executives and users will decide which are most important - Must select a system scope and level of automation - Methods of development are reviewed Assessing the Target Processing Environment - Target processing environment o Configuration of computer equipment, operating systems and networks that will exist when the new system is deployed - Must be a stable environment to support the new system - Design and implementation of the processing environment is one of the early activities in moving from analysis to design Centralized Systems - Prior to the early 1970’s there was only one environment – the mainframe computer system at a central location - Options focused around what kind of input or output to these large systems - Common to large-scale batch processing applications (e.g. banking, insurance, government etc.) where: o Some input transactions don’t need to be processed in real time o On-line data entry personnel can be centrally located o Large numbers of periodic outputs are produced - Often used for a subsystem of a larger, sometimes distributed information system Single Computer Architecture - Places all information system resources on a single computer system and its attached peripherals - Requires all users be located near the computer - Advantage is simplicity and ease of maintenance - However, many systems require more computing power than one single machine can provide Clustered and Multicomputer Architectures - A group of computers of the same type that have the same operating environment and share resources - Computers from the same manufacturer are networked - Clusters act like a single large computer system - One may act as entry point and the others function as slave computers Multicomputer Architecture - A group of dissimilar computers that are linked together but the hardware and operating systems are not required to be a similar as in the clustered architecture - System still functions like one single large computer - Can have central computer and slave computers o Main computer may execute programs and hold database o The front-end computer may handle all communication Notes on Centralized Systems - Clustered architectures may be cost efficient if similar operating system is used by all - Multicomputer architectures are good when the centralized system can be decomposed into relatively independent subsystems (each possibly with its own operating systems Distributed Computing - Distributed computing o The approach to distributing a system across several computers and locations - E.g. corporate financial data might be stored on a centralized mainframe, linked to minicomputers in regional office and personal computers at more locations - Relies on computer networks to connect up the systems Client-Server Architecture - Currently the dominant architectural model for distributing information resources o Server computer (server): A computer that provides services to other computers on the network o Client computer: A computer that requests services from other computers on the network - E.g. print server on a network, that clients (other PCs on the network) can send print jobs to - Middleware o Computer software that implements communication protocols on the network and helps different systems communicate - Data layer o A layer on a client-server configuration that contains the database Three Layer Client-Server Architecture - An information system application program can be divided into the following set of client and server processes or layers - Three-layer architecture o The data layer  Manages stored data, implemented as one or more databases o The business logic layer  Implements the rules and procedures of business processing o The view layer  Accepts user input, and formats and displays processing results - View layer acts as client of the business logic layer, which acts a a client of the data layer Notes on Three Layer Architecture - Easy to distribute and replicate over a network - Layers are relatively independent of each other - Can be expanded into a larger number of layers - N-layer architectures, or n-tiered architectures o A client-server architecture that contains n layers The Internet and Intranets - Internet: a global collection of networks that are interconnected using a common low-level networking standard – TCP/IP (Transmission Control Protocol/Internet Protocol) - Services provided by the Internet o E-mail protocols (Simple Mail Transfer Protocol – SMTP) o File transfer protocols (e.g. File Transfer Protocol – FTP) o Remote login and process execution protocols (e.g. Telnet) Intranets and Extranets - Intranet o A private network that is accessible to a limited number of users, but which used the same TCP/IP protocol as the Internet o Restricted access – firewalls, passwords, unadvertised - Extranet o An intranet that has been extended outside of the organization to facilitate the flow of information (e.g. access to suppliers, customers, and strategic partners) o Allows organizations to exchange information and form a virtual organization - The Web is organized as a client-server architecture o Web processes are managed by server processes that execute on dedicated servers and clients send requests to servers using a standard web resource request protocol The Internet as an Application Platform - The Internet provides an alternative for implementing systems o E.g. RMO buyer can access the system while on the road – the client portion of the application is installed on their laptop computers (uses modem to connect) o Alternatively, using the WWW for accessing the remote site, all the buyer needs is a web browser and is now accessible from any computer with Internet access - Use of the Internet greatly expands accessibility and eliminates need to install custom client software – also cheaper to put up on the Web Advantages of WWW over Traditional Client-Server Approaches - Accessibility o Web browser and Internet connections are nearly ubiquitous and are accessible to large numbers of users - Low-cost communication o High-capacity WAN form the Internet backbone are funded primarily by governments (a company can use the Internet as a low-cost WAN) - Widely implemented standards o Web standards are well known and many computer professionals are trained in their use o Use of intranet or extranet enjoys all the advantages of web delivery o Really represents evolution of client-server computing to the WWW Negative Aspects of Application - Security o Web servers are well-defined target for security breaches - Reliability o Internet protocols do not guarantee a minimum level of network through put or that a message - Throughput o Data transfer capacity of many users limited by analog modems to under 56 kilobits per second - Volatile standards o Web standards change rapidly Development and System Software Environments - Development environment o Consists of standards and tools used in an organization o E.g. CASE tools, programming standards - System software environment o Includes operating system, network protocols, database management systems etc. - Important activity during analysis o To determine the components of the environment that will control the development of the new application Important Components of the Environment that will affect the Project - Language environment and expertise o Companies often have preferred languages o Numerous languages out there – COBOL, C++, Visual Basic, to web- based languages like Java and Perl Script o Choosing a new language requires additional work - Existing CASE tools and methodologies o If a company has invested heavily in a CASE tool then all new development may have to conform to it - Required interfaces to other systems o A new system typically must provide information to and receive it from existing systems - Operating System environment o Strategic goals may exist to change the operating system o Multiple platforms may be needed o Legacy systems are often still there and may be linked to newer client- server applications and databases - Database management system (DBMS) o Many corporations have committed to a particular database vendor o May require a distributed database environment with portions distributed over the country Rocky Mountain Outfitters Example - Current Environment o Mainframe at Park City data center o Mail order and distribution functions are connected directly to the mainframe to allow real-time connection o Mainframe application written in COBOL and DB2 database used o Dialup telephone lines are used to communicate with manufacturing sites in Salt Lake city - Proposed Environment o Strategic plan gets changed as new systems are developed o Various target environments possible for RMO  Move to Internet technology  Utilize internal LNA/WAN technology  Use a mix of the two options o Other alternatives  Use a mainframe central processor  Distributed
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