n-layared architecture, is it only a 3 layer thing?

Question

I've always heard about the 3 layer approach (Presentation + Business logic + Data access) and that's the way I've always worked (adding a "4" layerif I count the database itself), but I'm wondering if this is all about layer and tier architecture (I already know the difference between layer and tier), is there a 5+ tier approach?, I've also heard about the controller, service and the application tier, how does this fit on the context?

Thank you,

Answer 1

There can be several layers. Do not confuse layers with tiers. Article explaining the difference: http://davidhayden.com/blog/dave/archive/2005/07/22/2401.aspx

Five layers:

RIA -> ASP.Net MVC -> WebService -> Business layer -> ORM.

It simply boils down to what you need and how you implement those requirements. I would not stare me blind on layers but to make sure that everything follows Single Responsiblity principle and Don't Repeat yourself. Doing so will often lead to different layers naturally.