Business Logic Layer importance

3 tire applications are used for the Distributed Processing.
Each layer has to perform its own task.
They can be separated through to their functionality

1) UI or Presentation Layer -- For the Interface to the client. It is used to display the Data the client as a GUI format.
2) BLL or Application Logic -- For validating the data as per the rule for the business. It works as a real world object. All the functionality is defined in this class and used to display the details in the Presentation Layer. It is a bridge between Data Access layer and Presentation Layer. It reduces the validation check to the Database server. So Database does not get overloaded.
3) Data Access Layer -- To perform the task related to the database.
http://www.dotnetspider.com/forum/166716-tire.aspx
http://en.wikipedia.org/wiki/Business_logic

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Hi Thanks Neek for your valuable post,
But when i said like your post interviewer not agreed . Please can you explore your response with sample code . Thanks .

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The BLL Is a Business Logic Layer. That is where We manage the Business Rules before they are passed to the Data Layer. We use BLL to make sure what is going to DAL is Clean. e.g

For Registration in a Website there might be a Business Rule that says if you are below 18 of age , you can never register and there Can be a Business Rule that says if your age is less than 18 attachment your Parent e-mail address for aproval, if now this cannot be Trapped in the PL(Presentation Layer), you have to trap it in your BLL. That is why you have BLL

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Hi thanks for your reply,
Without using that BLL , can't we do that in UI layer? or in DAL?
Please reply me urgent.

Thanks Vuyiswamb .

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Because we can extend the application easily. And you can separate different machines as per the Layers. Means you can keep different Layers on Different Machines

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Thanks for your clear information Mr.Neeks.Please keep going on..

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