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Chapter 10

Site

Architecture

McGraw-Hill/Irwin Copyright © 2004 by The McGraw-Hill Companies, Inc. All rights reserved.

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Chapter 10: Site ArchitectureChapter 10: Site Architecture

Questions answered by this chapter:• What is logical architecture?• What are the factors involved in choosing a

logical architecture?• What is the presentation layer?• What is the business logic layer?• What is the data layer?• What are the factors involved in choosing a

physical architecture?

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Logical vs. Physical ArchitectureLogical vs. Physical Architecture

• Logical Architecture– Attempts to define the system in terms of

its software components and the desired functionality of those components

• Physical Architecture– Defines the hardware and third-party

software needed to host and maintain a website

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Logical ArchitectureLogical Architecture

Four main logical models have evolved over the years:

• Mainframe: systems are built around a single, monolithic computer that is shared by all users on the system

• Client/Server: a central server is used to store information that is accessed and acted upon by any number of client machines connected to the server through a network

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Exhibit 10-1: Mainframe ArchitectureExhibit 10-1: Mainframe Architecture

Dumb Terminals (no CPU)

Single Mainframe Computer

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Exhibit 10-2: Client/Server ArchitectureExhibit 10-2: Client/Server Architecture

PC Workstations

Single Central Server

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• N-Tier: compartmentalizes different functions of a system into modules that interact with one another

• Distributed: is a system of servers, loosely coupled across a dispersed network, that work together to deliver a website

Logical Architecture Logical Architecture (cont’d)(cont’d)

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Exhibit 10-3: N-Tier ArchitectureExhibit 10-3: N-Tier Architecture

Presentation LayerBusiness Logic Layer

Data Layer

PCs with Web Browsers

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Exhibit 10-4: Distributed ArchitectureExhibit 10-4: Distributed Architecture

Three-Tier System

PCs with Web BrowsersExternal Payment

Processing

Internal Inventory System

Internal Link

External Link

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Choosing an ArchitectureChoosing an Architecture

• A number of factors can influence this decision, they can include:– Functionality: refers to the functions that a system must

implement

– Flexibility and Adaptability: refer to the ability of a system to adapt to changes in its function

– Scalability: refers to the ability of a system to be extended to handle a greater load, usually as a result of an increase in the user base

– Performance: is the perceived speed of a system, often measured by the user as response time

– Maintenance: refers to the monitoring and updating of a system

10-12Exhibit 10-5: CNN Homepage Exhibit 10-5: CNN Homepage (August 23, 2001, and September 11, 2001)(August 23, 2001, and September 11, 2001)

CNN.com Homepage August 23, 2001

CNN.com Homepage September 11, 2001

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Choosing an Architecture Choosing an Architecture (cont’d)(cont’d)

– Required Skills: refers to the skills needed to design, build, and maintain a system

– Security: refers to the ability of a system to prevent illegal or inappropriate use of its data and to deter hackers

– Reliability: refers to the amount of time a system can be expected to be available to users

– Metrics: are the measurements and data needed by the company to understand the operation of a system

– Cost: is the amount of money spent to design, build, and maintain a system

– Time: refers to the number of people/hours, as well as total time period, needed to develop a system

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Exhibit 10-6: Three-Tier ArchitectureExhibit 10-6: Three-Tier Architecture

Web Server

Payment User/Admin Content

Database

Presentation

Business Logic

Data

Modules

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The Data LayerThe Data Layer

• The main function of the data layer is to provide fast, reliable access to data needed to run a system

• Additionally, the data layer is responsible for maintaining information about the relationships between data

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Types of DatabasesTypes of Databases

• Flat-File: are single computer files that store all of the information for a system

• Relational: data are stored in a series of tables, each table stores a discrete piece of data for the system

• Object Oriented: encapsulates all data into different types of objects

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Choosing a DatabaseChoosing a Database

• To choose the right database several factors must be weighed:– Load/Storage Capacity– Type of Data– Speed– Cost– Reliability

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The Business-Logic LayerThe Business-Logic Layer

• The business-logic layer is responsible for implementing the basic rules of the system according to the operating rules of the business

• This layer is often divided into a number of submodules, each handling different aspects of the system

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The Presentation LayerThe Presentation Layer

• The presentation layer is responsible for all communications with the user’s computer

• The most common ways to present data to site users are:– HTML– Third-party Plug-ins– Homegrown Plug-ins

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Exhibit 10-7: E! Online Plug-InsExhibit 10-7: E! Online Plug-Ins

Macromedia Flash Plug-In

Microsoft Media Player Plug-In

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External SystemsExternal Systems

• Kinds of systems most often connected with a companies site include:– CRM– Payment Processing– Shipping– Fulfillment– Inventory– Financial– Human Resources– B2B Exchanges– Outside Suppliers

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Physical ArchitecturePhysical Architecture

Hardware

• When choosing hardware, a number of factors must be considered:– Platform– Power– Hosting

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Hosting AlternativesHosting Alternatives

• Free: – Hosts offering free service (ex., geocities.yahoo.com)– Good for very simple sites (personal homepages)

• Shared Server: – Many websites are placed on the same Web server– Good for small businesses looking for increased capabilities

• Dedicated Server: – Website is allocated its own dedicated server– Good for larger websites

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Hosting AlternativesHosting Alternatives

• Co-located Server:– Offers companies the most control over the

hardware running the site– Customer owns server and is only paying for

bandwidth and a physical space for the server

• In-house:– Good for companies with adequate resources

(Global 1000 companies)– Sites need 24-hr dedicated personnel, power

backup, security maintenance, and redundancy

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Hosting for Large WebsitesHosting for Large Websites

• Most large websites are hosted by third-party facilities

• The main service offered by these companies is reliability

• Typical service offerings from third party companies include:– Redundant Internet Connections– Backup Power– Physical Security– Server Management Services– Offsite backup Storage