Web Applications

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Web Applications
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In this chapter, you will learn

• How Internet databases are typically used
• About the architecture of Web-to-database
  middleware
• How Web-to-database middleware is used to
  integrate databases with the Internet
• What special considerations govern Web database
  development

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Web Database Connectivity

• Allows rapid response to competitive pressures
• New services
• New products
• Customer support enhanced
• Fast effective information dissemination
• Universal access
• Local
• Around the globe

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Typical Uses of Internet
Table 15.2
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Characteristics/Benefits of Internet Technology

• Hardware software independence
• Cost savings
• Uses existing equipment
• Platform independence and portability
• No need for multiple platform development
• Common simple user interface
• Reduced training
• Reduced support

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Characteristics/Benefits of Internet Technology

• Location Independence
• Global access through Internet
• Reduced costs for dedicated connections
• Rapid development at manageable costs
• Development tools
• Low entry costs
• Available software access tools

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Web-to-Database Middleware

• Server-side extension
• Interacts directly with Web server
• Handles specific requests
• Also known as Web-to-database middleware
• Examples
• ColdFusion
• CGI
• API
• JSP, Servlet

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Web-to-Database Middleware
Figure 15.1
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Web Server Interfaces

• Common Gateway Interface (CGI)
• Uses script files to connect to database
• Perl, C, VB
• Application Programming Interface (API)
• Newer and more efficient
• Uses DLLs
• Memory resident and faster
• Well known APIs
• Netscape (NSAPI)
• Internet Server API from Microsoft (ISAPI)
• WebSite API from OReilly (WSAPI)

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API and CGI Web Server Interfaces
Figure 15.2
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Web-to-Database Middleware Connection Methods

• Native SQL access middleware
• Use services of Open Database Connectivity (ODBC)
• Use Object Linking and Embedding Database (OLE
  DB) interface with Windows
• ODBC most common

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ODBC to Access Databases
Figure 15.3
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Web-to-Database Middleware Uses ODBC to Access
Databases
Figure 15.4
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Web Browser

• Located on the client computer
• End user Web interface
• Interprets HTML code received from Web server
• Presents page components in a standard way
• Client-side extensions
• Plug-ins
• Java and JavaScript
• ActiveX and VBScript

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The Web as a Stateless System

• Web server does not know status of any client at
  any given time
• Request-reply model of communication
• Browser concerned only with current page
• Data processing requires additional software
• Java, JavaScript, VBScript

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Internet Database Special Considerations

• Involve more than just database-enabled Web
  applications
• Issues important to corporate databases
• Data security
• Transaction management
• Client-side data validation
• Operational and management challenges
• Database applications development most affected
  by Internet

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Data Security

• Web Server Level
• Secure transactions using encryption
• TCP/IP protocol level
• Firewalls
• RMDBS Vendors
• Login authentication
• Restrict access to particular SQL commands
• Web-to-database middleware
• End user restrictions
• Designer created algorithms
• Must support e-commerce applications

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Transaction Management

• Concept is foreign to Web
• Dilemma created by request-reply model
• Web cannot maintain open line between client and
  database
• Recovery requires client maintain open
  communications
• Designers must ensure proper transaction
  management support at database server level

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Denormalization

• Web forms
• Cannot control data entry
• 1M relationships problematic (not dynamic) (Ex
  invoice / invoice line)
• Solutions
• Web programming languages
• Java, JavaScript, VBScript

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JSPs

• JSP tutorial http//java.sun.com/j2ee/tutorial/
  1_3-fcs/doc/JSPIntro.html
• Bookstore example.

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