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AJUG: Layers in SUN World

 
Oghie Ojior
Greenhorn
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Layers are logical units in software. Each layer in the software is responsible for a specific task in an application.
In theory there are 6 layers in software:
Presentation manager
Presentation logic
Application logic
Business logic
Database logic
Database manager
Are these the same layers SUN is referring to?
 
Ajith Kallambella
Sheriff
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"Tier" is perhaps a better parlance than "layer". In the J2EE world, we always speak of three prominent tiers viz., Client Tier(aka Presentation tier), Application Tier( aka Middle Tier) and the Database Tier(aka Persistence tier ). Some architectures include an Enterprise Information Systems(EIS) tier in addition to/instead of Database Tier. The entire set of component technologies offered by the J2EE platform can be divided into these four tiers.
The term layer is often used in the context of design patterns, to distinguish the boundaries between collaborating components. Pesonally I prefer using the term "tier".
Cheers,
 
Jack Zhou
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I think, term tier focus on the physical distribution for your application components. Layers are a way to organize the softeware pieces according to their functionality. So I understand in a 2-tier app with a fat client. The client tier could contain both the persentation layer and business logic layer. a 2-tier app with a thin client, the business logic layer is on the server tier. May be most of time, tier and layer align with each other. I would think more layrs increases maintanablity and flexbility while more tiers decrease the managebility. Just my opinon
 
Joseph Zhou
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There is SunTone methodology describes 3 aspects of an architectural framework
1.tiers - application partitioning
client
presentation
business
integration
resources
2.layers - hardware/software stack
application
virtural platform - API or spec.
upper platform - middleware
lower platform - OS
hardware
3.Systemic qualities
the 8 characteristics: performance...
 
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