| Author: veeresh 03 Jan 2007 | Member Level: Diamond | Rating:  Points: 2 |
A 3-tier application is a program which is organized into three major disjunctive
tiers. These tiers are
Presentation Tier (Front end)
Logical Tier (Middleware)
Data Tier (Backend).
Each layer can be deployed in geographically separated computers in a network. Some architects divide Logic Tier in to two sub tiers Business and Data Access Tiers, in order to increase scalability and transparency. The tiers can be deployed on physically separated machines. The characteristic of the tier communication is that the tiers will communicate only to their adjacent neighbors. For an example, The Presentation Tier will interact directly with the Business Tier and not directly with Data Access or Data Tiers.
Presentation Tier:
This Tier is responsible for communication with the users and web service consumers and it will use objects from Business Layer to response GUI raised events.
Business Tier
This sub tier contents classes to calculate aggregated values such like total revenue, cash flow and ebit and this tier doesnt know about any GUI controls and how to access databases. The classes of Data Access Tier will supply the needy information from the databases to this sub tier.
Data Access Tier:
This tier acts as an interface to Data Tier. This tier knows, how to (from which database) retrieve and store information.
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| Author: Vadivel Mohanakrishnan 03 Jan 2007 | Member Level: Diamond | Rating: Points: 2 |
http://en.wikipedia.org/wiki/Three-tier_(computing) -- this would give you a good explanation about this topic.
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