ITEC 2010 A chapter 8 Environments, Alternatives and Decisions

1. ITEC 2010 Achapter 8 Environments, Alternatives and Decisions

2. 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 focus of chapter 8 is on the last three activities (the transition from analysis to solutions and design)

3. 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

4. Assessing the Target Processing Environment • Target processing environment • 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

5. Centralized Systems • Prior to the early 1970’s there was only one environment – the mainframe computer system at a central location • Options focussed 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: • Some input transactions don’t need to be processed in real time • On-line data entry personnel can be centrally located • Large numbers of periodic outputs are produced • Often used for a subsystem of a larger, sometimes distributed information system

6. 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

7. 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

8. 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 • Main computer may execute programs and hold database • The front-end computer may handle all communication

10. Notes on Centralized Systems • Clustered architectures may be cost efficient if similar operating system is used by all • Multicomputer architectures are good when the the centralized system can be decomposed into relatively independent subsystems (each possibly with its own operating systems

11. Distributed Computing • Distributed computing • 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

12. Computer Networks • Computer network • A set of transmission lines, equipment and communication protocols to permit sharing of information and resources • Local area networks (LAN) • A computer network where the distances are local (e.g. in the same building) • Wide area network (WAN) • A computer network across large distances (e.g. city, province or nation)

14. LANs and WANs • Can be built from many technologies • E.g. ethernet and token rings • Can use asynchronous transmission mode • WANs may be constructed using purchased equipment and leased long-distance transmission lines • May be subcontracted from long-distance communication vendors (e.g. AT&T, Sprint etc.) • Many ways to distribute information resources • Users, application programs and databases can be placed on the same computer or different computers on different LANs

15. Client-Server Architecture • Currently the dominant architectural model for distributing information resources • Server computer (server): A computer that provides services to other computers on the network • 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 • Computer software that implements communication protocols on the network and helps different systems communicate • Data layer • A layer on a client-server configuration that contains the database

17. 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 • The data layer • Manages stored data, implemented as one or more databases • The business logic layer • Implements the rules and procedures of business processing • 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

19. 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 • A client-server architecture that contains n layers

21. 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 • E-mail protocols (Simple Mail Transfer Protocol – SMTP) • File transfer protocols (e.g. File Transfer Protocol – FTP) • Remote login and process execution protocols (e.g. Telnet)

22. The World Wide Web (WWW) • A collection of resources such as files and programs that can be accessed over the Internet using standard protocols, including • Formatted and linked document protocols, e.g. HyperTexst Markup Language (HTML), Extensible Markup Language (XML), and Hypertext Transfer Protocol (HTTP) • Executable program standards including Java, JavaScript and Visual Basic Script (VBScript) • The Internet is the infrastrcture upon which the WWW is based (ie. Resources are delivered over the Internet)

23. Intranets and Extranets • Intranet • A private network that is accessible to a limited number of users, but which used the same TCP/IP protocol as the Internet • Restricted access – firewalls, passwords, unadvertised • Extranet • 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) • Allows organizations to exchange information and form a virtual organization • The Web is organized as a client-server architecture • 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

24. The Internet as an Application Platform • The Internet provides an alternative for implementing systems • 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) • 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

25. Advantages of WWW over traditional client-server approaches • Accessibility • Web browser and Internet connections are nearly ubiquitous and are accessible to large numbers of users • Low-cost communication • 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 • Web standards are well known and many computer professionals are trained in their use • Use of intranet or extranet enjoys all the advantages of web delivery • Really represents evolution of client-server computing to the WWW

26. Negative Aspects of Application • Security • Web servers are well-defined target for security breaches • Reliability • Internet protocols do not guarantee a minimum level of network through put or that a message • Throughput • Data transfer capacity of many users limited by analog modems to under 56 kilobits per second • Volatile standards • Web standards change rapidly

27. Development and System Software Environments • Development environment • Consists of standards and tools used in an organization • E.g. CASE tools, programming standards • System software environment • Includes operating system, network protocols, database management systems etc. • Important activity during analysis • To determine the components of the environment that will control the development of the new application

28. Important components of the environment that will affect the project • Language environment and expertise • Companies often have preferred languages • Numerous languages out there – COBOL, C++, Visual Basic, to web-based languages like Java and Perl Script • Choosing a new language requires additional work • Existing CASE tools and methodologies • 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 • A new system typically must provide information to and receive it from existing systems

29. Operating System environment • Strategic goals may exist to change the operating system • Multiple platforms may be needed • Legacy systems are often still there and may be linked to newer client-server applications and databases • Database management system (DBMS) • Many corporations have committed to a particular database vendor • May require a distributed database environment with portions distributed over the country

30. Rocky Mountain Outfitters Example • Current Environment • Mainframe at Park City data centre • Mail order and distribution functions are connected directly to the mainframe to allow real-time connection • Mainframe application written in COBOL and DB2 database used • Dialup telephone lines are used to communicate with manufacturing sites in Salt Lake city

31. Proposed Environment • Strategic plan gets changed as new systems are developed • Various target environments possible for RMO • Move to Internet technology • Utilize internal LNA/WAN technology • Use a mix of the two options • Other alternatives • Use a mainframe central processor • Distributed client-server processors • Other considerations regard the database technology • Use traditional relational database technology • Or, move to objecct-oriented databases

32. RMO wants to be state-of-the-art • But wants to avoid high-risk projects • Strategic plan • Move away from COBOL mainframe environment • Move to combination of client-server configuration