Transcript Chapter 8
Chapter 8 Evaluating Alternatives for Requirements, Environment, and Implementation Deciding on Scope and Level of Automation • Decisions affecting requirements, environment,and implementation are made together because one area affects decisions in the other two • Systems scope and level of automation are closely related • Scope – defines which of the business functions will be included in the system • Level of automation– is how much computer support exist for the business functions that are included Controlling a Projects Scope • Scope creep– adding new system functions after the requirements have been defined and finalized • One way to control scope creep is to formalize the process of identifying, categorize, and prioritize the functions that will be included so that every one agrees to and signs off on systems functions • The event table is an effective technique to control project scope. Determine Level of Automation • Low The computer system only provides simple record keeping • High the system takes care of as much as possible, the processing associated with each function. Medium a combination of features from the high-level and low-level automation Defining the Application Environment • Application deployment environment—the configuration of computer equipment, operating systems, and networks into which the new application system will be installed. • Things to consider -transaction volume -number of users -location of users -data requirements -QOS requirement - stability requirements Processing Environment Alternatives • Centralized Single computer architecture Clustered and multicomputer architectures • Distributed computing Computer networks Client-Server architecture server- a computer that provides services to other computers on the network client –a computer that request services from other computers on the network N-Layer Client-Server Architecture • Typical Layers of an information system data layer – manages stored data, usually implemented as one of more databases business logic layer – implements the the program logic of the application view layer – the part of the client-server configuration that contains the user interface and other components to access the system Internet, Intranets, and Extranets • Internet – a global collection of networks using common low-level networking standard-TCP/IP • Intranet – a private network that uses Internet protocols but is accessible only by a limited set of internal users (usually members of the same organization or work group • Extranet –an internet that has been extended to include directly related business users outside the organization (such as suppliers, large customers, and strategic partners). Choosing Implementation Alternatives • Packaged software– software purchased to support a particular application and used as is. works well inexpensive less errors and more stable upward compatible can not be modified…must use the options avialable Turnkey software • An outside vendor provides a complete solution, including hardware and software. --often do not exactly meet the needs of the organization Enterprise Resource Planning – support all Operational functions of an entire organization --lower cost and risk --may not do exactly what is needed by the organization