What is a domain model ? Why is it preferred than a dataset in .net?

I was wondering, in assignments I have been using datasets. Now when I started working in this software company people开发者_C百科 are using something called DTO - data transfer object. Where does domain model come in ? What is it really ?

Thanks

DTOs are simple data structure objects that serve only to transfer data out of a database (often via an ORM) and make those data available to higher layers of the application. If a DTO is used to feed into a proper domain model layer, this is architecturally valid (though perhaps redundant). If you treat your DTOs as a domain model layer (in other words, you have no domain logic separate from the user interface), then you are using your DTOs as an anemic domain model, which is a severe architectural anti-pattern.

DTO = Data Transfer Object are as it sounds. Object that transfer data between system layers. The purpose is often to adapt the request and response data so it suits the use case. Example can be that you request a CV through a HR system's CandidateService in application layer. The Candidate Service loads information than spans over different domain entities: WorkExperince, Education, Personal Letter etc. To avoid a complex and massive response object graph we can flatten the repsponse by building a DTO object that is exactly design for what the client (GUI) needs.

There are a lot to say about DTO. But I do not want to write a novel :) But DTO do not belong in the Domain Model, in the Core. DTO is mostly refered in DDD as tool for communication between application services to clients, especially if you use web services (WCF etc). Then DTO is a perfect way of serializing part of your domain into a web service message (serialized DTO).

Hopefully you can ask your collegue/co-workers as well what they intended to accomplish with DTO's. There are several drawback with DTO's, usually it gives you an extra layer and that means more to do during maintenance phase...

(almost a novel by now) I use DTO's only when there is a really benefit and thats when you can deliver a complex responses with DTO that matches the clients needs exactly. Otherwise the client usually need to call different services or methods to gather enough information.