n-tier-architecture

I have a project where we use screen DTO's to encapsulate the data between the Service Layer and the Presentation Layer . In our case, the presentation layer is ASP.Net. The only classes that know about the DTO's are the service layer classes and the Pages/Controls that call these services and display the DTO's. The DTO's are almost always Page/Control specific so I feel they belong in the Presentation Layer, but that would mean the Service Layer would have to reference the Presentation Layer in order to use the DTO's. I'm almost thinking that the Service Layer should return richer objects

After spending a couple months studying DDD methodology, I've now began to apply these concepts into actual products at my company. In fact, I've been tasked with creating a suitable and maintainable architecture for future development. We have decided to make use of the following technologies: EF4 (really v2), Unity The amount of information I've obtained has been most enlightening, however, I'm left with several questions in best practice: Question #1: DTOs - Best Practices I have my domain objects (POCO classes). There are several ways to implement these classes. Traditional Approach:

I just came across the following sentence: As the industry has moved from a three tier model to n-tier models, the object relational impedance mismatch has become more prevalent. But I can't find a concise explanation of the difference between three tier and n-tier. I know what three tier is, and I assume n-tier just adds one or more tiers. I'm just not sure what these additional tiers would be. If anyone has a short explanation or simply a good link, that would be much appreciated. The quote appears to be from this codeproject page. It also seems to do a pretty good job of explaining n-tier

I am designing an ASP.NET MVC application using the Onion Architecture described by Jeffrey Palermo. It is an ASP.NET MVC 2.0 project, where I am requiring that all views be strongly typed using dedicated View Models -- we will not be passing domain models to our views. We are using AutoMapper to do the translation -- AutoMapper is isolated in the infrastructure, Web does not know or care that AutoMapper is being used. Currently, I am defining the IViewModelMapping interfaces in the Web project -- simply because this service will be used by the Controllers and it has direct access to its own

I'm dealing with the 3-tier architecture PHP website. Now I need to redesign it to suрроrt distributed n-tier architecture. After long hours of research i came to this solution: business logic should be separated into presentation and purely business logic tier to allow for n-layer architecture (user-interface,presentation tier,b.logic and data tier). I have decided to use РНР just for the presentation. In the business logic I want to use J2ЕЕ implementation technology instead of implementing it in PHP because J2EE can provide much more essential container services which are essential for