CSLA stands for Component-based, Scalable Logical Architecture, and is the result of over 10 years worth of research and development. The .NET implementation of CSLA was started in 1999, and development continues today.

CSLA .NET is a software development framework that helps you build a powerful, maintainable business logic layer for Windows, Web, service-oriented and workflow applications.

Check this link for more details: http://www.lhotka.net/cslanet/