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Layers and Tiers

I was in a conversation recently about the difference between a layer and a tier, in particular, are the two terms synonomous? My answer was that layers refer to specific layers of abstraction within an application (software) whereas tiers refer to the physical residence of those layers (hardware).

  • App.Layer == “Software“;  // logical
  • App.Tier == “Hardware“;  // physical

For instance, your UI components logically reside in the Presentation layer, but physically reside on your web server tier. Your business components, which are logically in the Business Logic layer, might reside on your app server tier. You probably also have database components that belong to the Data Access layer, but physically reside with your business components on the app server tier. See the difference?

Anyone else use these terms interchangeably? Anyone else have a different way of thinking about them?

Print | posted on Monday, June 14, 2004 10:31 PM

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# RE: Layers and Tiers

left by Darrell at 6/15/2004 6:45 AM
I do *not* use those interchangeably. One is to help developers, the other is to annoy the server admins.

# re: Layers and Tiers

left by Dave at 6/15/2004 7:27 AM
Darrell - Glad to see we agree :-)

# ͥĢ/2004-06-18

left by PukiWiki/TrackBack 0.1 at 6/17/2004 10:23 PM
?G VB6IDEg??G???? (via Dave Donaldson's Blog) 837910 Mouse wheel events do not work in the Visual Basic 6.0 IDE http://support.microsoft.com/default.aspx?scid=kb;EN-US;837910 IntelliPoint4.9'???...

# re: Layers and Tiers

left by NAV at 2/17/2005 1:29 PM
layers and tier are different.
while designing application one have to decide about both layer and tiers.
layers represents the logical view of the application while tier represents physical view of the application.
for example;

there are following layers:

presentation layer
business layer
data access layer
data layer
external system access layer



there are following tiers:

presenation tier
(have web server)
application tier
(have application server; ejb container)
data server tier
(have database; stored procedures;caching)



" layers are mapped to tiers "

1.you map presentation layer(html) to the presentation tier(web server)
2. map presentation layer(jsp) to the application tier(applicationn sever)
3.map business logic layer(java code) to the presentation tier(web server) in the form of embedded java code in jsp.



# re: Layers and Tiers

left by Dave at 2/17/2005 2:40 PM
NAV: Sounds like you and I agree :-)

# re: Layers and Tiers

left by guest at 3/30/2005 12:43 PM
agree

# re: Layers and Tiers

left by shivratan yadav at 5/2/2005 5:31 AM
Layers:---
A logical grouping of similar functionality within an application e.g in j2ee we group all the documentation part i.e html and jsp file in the same directory.
that refers to the presentation layer
All the .class file in web-inf/classes folder refers to business logic layer .


Tires-----A physical grouping of functionality within an application. e.g deploying
presentation layers(html and jsp) physically on the system i.e in the
...../Root/ .html
.jsp this is the directory structure of tomcat.

...../Root/web-inf/classes/ .class ------all the .class file should be placed here.

# re: Layers and Tiers

left by J. Babich at 12/6/2005 10:09 AM
For software architects there really does need to be a distinction between the physical distribution (tiers) and logical separation of components (layers). Because the same components may be distributed to multiple tiers, the term "tier" simply isn't granular enough to describe the architecture.

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