Chad Z. Hower's "Dude, Where's My Business Logic?"
Read this article. Please note that the terms "business logic" and "business logic layer" are used interchangeably with "Application Logic Layer" in industry. This layer represents the processing component of the Client-Server Architecture application (Two-Tier Application and/or Three-Tier Application).
Click http://www.codeproject.com/KB/architecture/DudeWheresMyBusinessLogic.aspx link to open resource.