chapter 14 designing distributed and internet systems

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Chapter 14 Designing Distributed and

Internet Systems

Modern Systems Analysisand Design

Fourth Edition

Jeffrey A. Hoffer Joey F. George

Joseph S. Valacich

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Learning Objectives Define key client/server, LAN, distributed database,

and middleware terms. Distinguish between file server and client/server

environments. Describe alternative distributed system designs. Describe standards for Internet-based system design. Describe options for ensuring Internet design

consistency. Describe site management issues. Describe issues related to managing online data.

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The Process of Designing Distributed and Internet Systems

Similar to designing single-location systemsDue to multi-location deployment, numerous design issues must be consideredMore opportunity for failure due to number of componentsMain issues involve ensuring reliability, availability, survivability, performance

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Deliverables and Outcome

Document that consolidates system design information: Description of each site Description of data usage for each site Description of business process for each site Contrasts of alternative IS architectures for

site, data and processing needs of each site

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Designing Systems for Local Area Networks (LAN)

LAN: the cabling, hardware, and software used to connect workstations, computers, and file servers located in a confined geographical areaMain LAN configuration options File Server architecture Client/Server architecture

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File Server Architectures

A device that manages file operations and is shared by each client PC attached to a LANDBMS use in a file server: One copy of the DBMS is on the file server

and concurrently running copies are on client PCs.

All data manipulation is performed on the client PC.

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Limitations of File ServersExcessive data movement

Entire data tables must be transferred instead of individual records

Need for powerful client workstations Each client workstation must devote

memory to a full DBMSDecentralized data control

Complicates record concurrency control, recovery, and security

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Cleint/Server Architectures

Application processing is divided between client and server.Client manages the user interface.Database server is responsible for data storage and query processing.

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Database engine: back-end DBMS software runs on the server to provide database processing and shared access for clients

Client: front-end software provides user interface and data manipulation functions

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Application Program Interface (API)

Software building blocks that ensure standardization of modules for data exchange between clients and serversCommon API interface can be used for communication between client and any kind of DBMS (DB2, SQL Server, MySQL, Oracle)

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Client/Server Advantages and Cautions

Advantages Leverages benefits of microcomputer technology Processing performed close to data source

Improves response time Reduces network traffic

Facilitates use of GUIs Encourages acceptance of open systems

Cautions Difficult migration from file server to client/server Compatibility issues Limited system design and performance monitoring

tools

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File Server vs. Client/Server

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Advanced Forms of Client/Server Architecture

Three-tiered client/server Three logical and distinct applications

Data management Presentation Analysis

Middleware Combination of hardware, software, and communication

technologies that bring together three distinct applications into one environment

Application Server Server where data analysis functions are performed

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Advantages of Three-tiered Architectures

Applications can be partitioned in a way that best fits the organizational computing need.Easier customization: application code resides on application server, so change done only in one place.Easier maintenance: data analysis is separate from user interface, so changing one can be done independently of the other.

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Approaches to Designing Client/Server Architectures

Distributed PresentationRemote PresentationRemote Data ManagementDistributed FunctionDistributed DatabaseDistributed Processing

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Distributed Presentation

Freshen up delivery of existing server-based applications, typically running on legacy mainframe computers, to distributed clients using screen scrapper technology

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Remote Presentation

All data presentation functions are on the client, providing greater flexibility of presentation than the distributed presentation option.

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Remote Data Management

All software except data management is on client, this is closest to the traditional client/server mode.

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Distributed Function

Analysis functions are split between client and server, with all presentation on client and all data management on server. Requires coordination between analysis function on client and server, making it difficult to develop and maintain.

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Distributed Database

Client has all functionality, except that data storage and management is shared between client and server. A distributed database is unstable, and it is very difficult to ensure compatibility and communication between client and server.

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Distributed Processing

Combines distributed function and distributed database, maximizing flexibility of analysis and data management

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Designing Internet Systems

Most new system development focuses on Internet-base applications (for internal processing, business-to-business, and business-to-consumer)Main design issues: Standards Separating content from display Future evolution Site consistency Site management Online data management

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Standards for Internet Design

Internet design is simpler than client/server due to proliferation of standardsTypes of Standards: Domain naming (BIND): a method for translating

domain names into Internet Protocol (IP) addresses

Hypertext Transfer Protocol (HTTP): a communication protocol for exchanging information on the Internet

Hypertext Markup Language (HTML): the standard language for representing content on the Web via command tags

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Separating Content from DisplayHTML has limitations due to format orientation of tagseXtensible Markup Language (XML) has been developed to separate content from displayXML: an Internet authoring language that allows designers to create customized tags that represent data transmitted between applications

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Future Evolution

Move from desktop PCs to thin clients Most processing and data storage occurs

on the server

Use of wireless mobile devices Wireless Access Protocol (WAP): a

wireless version of HTTP Wireless Markup Language (WML): a

wireless version of HTML

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Site Consistency

Professionalism requires a consistent look-and-feel across all pages of a Web siteAids to consistency: Cascading Style Sheets

A set of style rules that tells a Web browser how to present a document

Extensible Style Language (XSL) Specification for separating style from content when

generating HTML documents

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Site Management Issues

Customer Loyalty and Trustworthiness Conveyed by

Design quality Up-front disclosure Comprehensive, correct and current content Connected to the rest of the Web Data security Personalization Customization

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Site Management Issues (cont.)

Web Pages Must Live Forever Customer Bookmarks Links from Other Sites Search Engine Referrals Old Content Adds Value

System Security vs. ease of use “Remember my password” Use of cookies

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Online Data ManagementContext development Method of understanding how a system fits within

the existing business activities and data

Integration depth Measurement of how far a system penetrates into

the existing technology infrastructure

Organizational breadth Measurement that tracks the core business

functions affected by a system

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Context, Breadth and Depth

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Online Transaction Processing (OLTP)

Refers to immediate automated responses to the requests of usersDesigned to handle multiple concurrent transactionsPlays a large role in electronic commerce applications

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Online Analytical Processing (OLAP)

Refers to graphical software tools that provide complex analysis of data stored in a database.OLAP server is the chief componentGood for time series and trend analysisEnables user to “drill-down” into the data

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Merging Transaction and Analytical Processing

Requires combining operational and informational components

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Data Warehousing

Collection of data for decision supportKey features Subject-oriented: organized around key subjects Integrated: data are collected from many

operational systems and made to conform to standards

Time-variant: data contains a time dimension Nonvolatile: data cannot be updated by users

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Steps in Building and Using a Data Warehouse

Extract data from various source system files and databasesTransform, integrate, and load the dataData warehouse is a read-only environmentUsers access via query languages and analytical tools

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Data Warehouse ArchitecturesTwo-level Data warehouse and decision support environment

Three-level Operational systems Enterprise data warehouse

Centralized, integrated data warehouse Control point and single source of all data made available

to end users Data marts

A data warehouse that is limited in scope based upon aggregation and selection

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SummaryIn this chapter you learned how to: Define key client/server, LAN, distributed database,

and middleware terms. Distinguish between file server and client/server

environments. Describe alternative distributed system designs. Describe standards for Internet-based system

design. Describe options for ensuring Internet design

consistency. Describe site management issues. Describe issues related to managing online data.