YELLOW GROUP

SURVEY OF MULTITIER ENVIRONMENT

 

Introduction:

Multitier architecture offers a compelling way to develop client-server business solutions. It is technology-neutral and can be implemented on any vendor's technology that enables standard interfaces for each of the logical levels called "tiers." With an emphasis on clean interfaces between tiers, the implementation details are hidden from users. The functionality of each tier, called "components," can be written in many different languages and maintained independently. This capacity allows the developer to use many tools from his or her toolbox to get the job done quickly and correctly. Just as you wouldn't expect a carpenter to have only a hammer, a developer will not have only a single development tool.

 

Multitier Model

A multitier model allows developers to break down complex business processes into digestible pieces, allowing for reusability. The simplest form of a multitier model is the three-tier model. This document focuses on three-tiers for ease of explanation. You can further subdivide each tier into multiple tiers to gain complexity. The three-tier model nicely fits the client-server architecture (see Figure )

 

 

 

 

Client Level Tier:

The front-end client that communicates with the user through a graphical user interface. Client-side code at this level calls upon the available business-services level to provide encapsulated business functionality.

 

Business Level Tier:

The business-services tier is a relatively new concept, and it encapsulates business rules and processes enabling clarity of purpose for each individual object. A collection of detailed business objects, called a "component," is mixed with many other components at this level. Various business solutions call upon one or more of these business components, usually through the user-services tier, to provide a solution. Many business solutions can share a set of business objects.

 

Data Services Level Tier:

A collection of decision-independent data used by the business-services level to make decisions. This can be a database management system (DBMS). For example, it could be data stored on a mainframe or accessed from a bulletin board service or the Internet.

In short By implementing multitier design now will increase reusability and problems caused by inconsistent, "one-off" application will be eliminated.

 

A Complex Example of Distributed Multi Tier Environment: