Multitier Architecture

A Web server is part of a multitier application, sometimes referred to as an n-tier application. Multitier applications divide functionality into separate tiers (i.e., logical groupings of functionality). Tiers can be located on the same computer or on separate computers. Figure 19.2 presents the basic structure of a three-tier application.

Figure 19.2. Three-tier application model.

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The bottom tier (also called the information tier or the data tier) maintains data for the application. This tier typically stores data in a relational database management system (RDBMS). For example, a retail store might have a database of product information, such as descriptions, prices and quantities of items in stock. The same database also might contain customer information, such as user names for logging into the online store, billing addresses and credit card numbers.

The middle tier (also called the business logic tier) implements business logic to control interactions between application clients and application data. It acts as an intermediary between data in the information tier and the application clients. The middle-tier business logic receives client requests from the top tier (e.g., a request to view a product catalog), retrieves and processes data from the information tier, and sends the result back to the client.

Business logic in the middle tier enforces business rules and ensures that data is reliable before updating the database or sending data to a user. Business rules dictate how clients can and cannot access application data and how applications process data. For example, a business rule can specify how to convert numeric grades to letter grades.

The top tier (also called the client tier) is the application's user interface. Users interact directly with the application through the user interface. The client tier interacts with the middle tier to make requests and to retrieve data from the information tier. The client tier then displays to the user the data retrieved from the middle tier.

Introduction to Computers, the Internet and World Wide Web

Introduction to C++ Programming

Introduction to Classes and Objects

Control Statements: Part 1

Control Statements: Part 2

Functions and an Introduction to Recursion

Arrays and Vectors

Pointers and Pointer-Based Strings

Classes: A Deeper Look, Part 1

Classes: A Deeper Look, Part 2

Operator Overloading; String and Array Objects

Object-Oriented Programming: Inheritance

Object-Oriented Programming: Polymorphism


Stream Input/Output

Exception Handling

File Processing

Class string and String Stream Processing

Web Programming

Searching and Sorting

Data Structures

Bits, Characters, C-Strings and structs

Standard Template Library (STL)

Other Topics

Appendix A. Operator Precedence and Associativity Chart

Appendix B. ASCII Character Set

Appendix C. Fundamental Types

Appendix D. Number Systems

Appendix E. C Legacy Code Topics

Appendix F. Preprocessor

Appendix G. ATM Case Study Code

Appendix H. UML 2: Additional Diagram Types

Appendix I. C++ Internet and Web Resources

Appendix J. Introduction to XHTML

Appendix K. XHTML Special Characters

Appendix L. Using the Visual Studio .NET Debugger

Appendix M. Using the GNU C++ Debugger


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C++ How to Program
C++ How to Program (5th Edition)
ISBN: 0131857576
EAN: 2147483647
Year: 2004
Pages: 627
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