Modern Systems Analysis
and Design
Fourth Edition
Jeffrey A. Hoffer
Joey F. George
Joseph S. Valacich
Chapter 14
Designing Distributed and
Internet Systems
© 2005 by Prentice Hall
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 systems
Due to multi-location deployment, numerous
design issues must be considered
More opportunity for failure due to number of
components
Main issues involve ensuring reliability,
availability, survivability, performance
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Deliverables and Outcome
Document that consolidates system
design information:
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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 area
Main LAN configuration options
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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 LAN
DBMS use in a file server:
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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 Servers
Excessive 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 DBMS
Decentralized data
control
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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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Client: front-end software provides user interface and data
manipulation functions
Database engine: back-end DBMS software runs on the server to
provide database processing and shared access for clients
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Application Program Interface
(API)
Software building blocks that ensure
standardization of modules for data
exchange between clients and servers
Common 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

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Leverages benefits of microcomputer technology
Processing performed close to data source
 Improves response time
 Reduces network traffic

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Facilitates use of GUIs
Encourages acceptance of open systems
Cautions
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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
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Middleware
 Combination of hardware, software, and communication
technologies that bring together three distinct
applications into one environment
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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 Presentation
Remote Presentation
Remote Data Management
Distributed Function
Distributed Database
Distributed 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:
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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 standards
Types of Standards:
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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 Display
HTML has limitations due to format
orientation of tags
eXtensible Markup Language (XML) has
been developed to separate content from
display
XML: 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
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Most processing and data storage occurs
on the server
Use of wireless mobile devices
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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 lookand-feel across all pages of a Web site
Aids 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
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Customer Bookmarks
Links from Other Sites
Search Engine Referrals
Old Content Adds Value
System Security vs. ease of use
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“Remember my password”
Use of cookies
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Online Data Management
Context development
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Method of understanding how a system fits within
the existing business activities and data
Integration depth
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Measurement of how far a system penetrates into
the existing technology infrastructure
Organizational breadth
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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 users
Designed to handle multiple concurrent
transactions
Plays 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 component
Good for time series and trend analysis
Enables 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 support
Key features
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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 databases
Transform, integrate, and load the data
Data warehouse is a read-only
environment
Users access via query languages and
analytical tools
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Data Warehouse Architectures
Two-level
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Data warehouse and decision support
environment
Three-level
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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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Summary
In this chapter you learned how to:
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
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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.
© 2005 by Prentice Hall
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Modern Systems Analysis and Design Ch14