What are the main recommendations when implementing layering in Visual Basic .NET?
Layers represent a build-up of functionality. The higher layers are dependant on the lower layers to supply the required information and methods. A single layer represents a logical group of functionality that is contained in an application tier that usually corresponds to functionality that is bound to a physical resource such as a database server. In this way, application tiers are composed of one or more logical layers that build the functionality provided by the tier. It is important to keep in mind that lower layers should almost never rely on higher layers for operation. A group of layers usually present a coherent whole. For example, you may be familiar with the concept of dividing an application among various tiers that are composed of groups of layers, such as the presentation tier (UI), the business logic tier (functionality), the data tier (storage and retrieval), and so on. Each tier represents a coherent unit of the application and serves a single purpose, such as displayi
