A Business Entity is a reusable, modular component that encapsulates all access to a particular set of related application data identified by its use within your application, for example, a Customer or an Order. A Business Entity becomes a type of service, one that can be called from any part of your application needing to retrieve or update data.
One advantage of encapsulating access to your data along with all the business logic that applies to it is that you can substitute a new user interface without having to change your business logic in any way. For this reason, when you consider how to integrate a new generation of user interface based on the GUI for .NET with your existing data and business logic, you should consider how best to keep the data and logic that you already have, while separating that logic from the specifics of the UI. While there is no requirement to re-architect your application to use the GUI for .NET, you should take advantage of the opportunity where you can to make a clean separation of the "client" side of your application (where the user interface is defined), from the "server" side of your application (where the data and business logic are encoded). This is true whether your application is actually divided between OpenEdge client sessions and AppServers, or whether it uses OpenEdge client-server support within a single session.
Many of the coding examples you will be seeing in documentation materials for OpenEdge 10.2 show GUI for .NET forms and their supporting code interacting with Business Entities and other data management components. This is referred to in OERA terminology as the Presentation Layer. For examples of GUI for .NET forms and their supporting code, see OpenEdge Getting Started: Introducing the Progress Developer Studio for OpenEdge Visual Designer.
