What are the pros and cons of using a Data Services Layer?

This is a discussion that seems to reappear regularly in the SOA world. I heard it as far back as '95, but it's probably been a topic of conversation long before that. I definitely have my own opinions about it, 开发者_JS百科but I'd like to hear some good, solid arguments for having a Data Services Layer, and likewise for arguments against having one.

What value does it add to a systems architecture? What are the inherent pitfalls? What are common anti-patterns?

Links to articles are definitely acceptable.

To avoid confusion, this article describes the type of Data Service Layer I'm talking about. Essentially, a thin layer above the database that provides SOAP access to data and includes no business logic.

---

Data services are quite data oriented, for projects without logic always doing crud. For instance, it can suit if you have a log service or a properties service, you will just do the crud to it.

If the domain that involves that DDBB is complex, with complex logic, you will need to manage that logic up to that service (maybe in an orchestration), so you will divide the logic into several services. In that case I think is better to use a thicker unique service (DAL, BLL and SIL) that manage that domain and expose just one interface.

At the end it is another tool, depend of the problem.