n tier applications

[Frazer]

hi
I would like to know what n tier applications are (i thought i already knew
that).
I had developed an applicaton that had a DAL layer, BLL layer, database and
user interface layer. what exactly is a layer? i had one .net solution file
and in that i had different projects representing these layers.
I thought thsi is a n tier application. but one of my friends in uni thinks
its not. am i correct in saying that all the tiers in an n tier app may not
reside on different servers. also my applicaiton was in C# and sql server. i
would like to see a real world .net application. anyone know any good links?

please give me as much input as possible as i am very new to this area.

warm regards

 

[Nick Malik]

The pattern that used to be called N-Tier is no longer discussed in the
formal literature, partly because it ended up with so many meanings. The
meaning that you refer to (as described by your post) is now called
"Layers". See the following link
http://msdn.microsoft.com/library/d...-us/dnpatterns/html/ArcLayeredApplication.asp

Your use of the term is perfectly fine. Most of the emphasis on n-tier was
a logical seperation for the sake of reducing coupling, enhancing cohesion,
and improving reusability and testability.

As I mentioned, the term had many meanings. One of the other common uses
for it was to describe a distributed system where various layers would run
at specific logical locations on different machines. This use has largely
been supplanted with Service Oriented Architectures.

I hope this helps,
--- Nick Malik

 

[Mike McIntyre [MVP]]

Hello Frazer,

Tier and layer mean the same thing.

It is the separation of the Presentation tier, Business Logic tier, and Data
tier (plus other tiers depending on the application) that makes an
application nTier, not physical separation on different computers. In
practice the tiers are generally on different compters.

Here are some links:

http://msdn.microsoft.com/library/d...us/dnbda/html/bdadotnetarch001.asp?frame=true

http://encyclopedia.thefreedictionary.com/N tier architecture

http://www.developerfusion.com/show/3058/2/


--
Mike

Mike McIntyre
Visual Basic MVP
www.getdotnetcode.com