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10-2 Chapter 10 Site Architecture McGraw-Hill/Irwin Copyright © 2004 by The McGraw-Hill Companies, Inc. All rights reserved.

10-3 Chapter 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?

10-4 Logical 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

10-5 Logical 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

10-6 Exhibit 10-1: Mainframe Architecture Dumb Terminals (no CPU) Single Mainframe Computer

10-7 Exhibit 10-2: Client/Server Architecture PC Workstations Single Central Server

10-8 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 (cont’d)

10-9 Exhibit 10-3: N-Tier Architecture Presentation Layer Business Logic Layer Data Layer PCs with Web Browsers

10-10 Exhibit 10-4: Distributed Architecture Three-Tier System PCs with Web Browsers External Payment Processing Internal Inventory System Internal Link External Link

10-11 Choosing 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

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

10-13 Choosing an Architecture (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

10-14 Exhibit 10-6: Three-Tier Architecture Web Server PaymentUser/AdminContent Database Presentation Business Logic Data Modules

10-15 The 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

10-16 Types 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

10-17 Choosing a Database To choose the right database several factors must be weighed: –Load/Storage Capacity –Type of Data –Speed –Cost –Reliability

10-18 The 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

10-19 The 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

10-20 Exhibit 10-7: E! Online Plug-Ins Macromedia Flash Plug-In Microsoft Media Player Plug-In

10-21 External 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

10-22 Physical Architecture Hardware When choosing hardware, a number of factors must be considered: –Platform –Power –Hosting

10-23 Hosting 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

10-24 Hosting 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

10-25 Hosting 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