itec 2010 a chapter 8 environments alternatives and decisions l.
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ITEC 2010 A chapter 8 Environments, Alternatives and Decisions 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

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major activities in the analysis phase
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)

the end of the analysis phase
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
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
centralized systems
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
single computer architecture
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
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
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
notes on centralized systems
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
distributed computing
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
computer networks
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)
lans and wans
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
client server architecture
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
three layer client server architecture
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
notes on three layer architecture
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
the internet and intranets
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)
the world wide web www
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)
intranets and extranets
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
the internet as an application platform
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
advantages of www over traditional client server approaches
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
negative aspects of application
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
development and system software environments
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
important components of the environment that will affect the project
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
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
rocky mountain outfitters example
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
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
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