Business Services and Other Middle-Tier Services Business services are the bridge between user and data services. They accomplish this by applying formal procedures and business rules to the relevant data. When the needed data resides on a database server, they secure the data services needed to accomplish the business task or apply the business rule. This insulates the user from direct interaction with the database. A business task is an operation defined by the application s requirements, such as entering a purchase order or printing a customer list.
Business rules are policies that control the flow of the business tasks.
For example, a procedure that applies a certain percentage markup to an inventory item in order to generate a customer invoice, is a business rule. Because business rules tend to change more frequently than the specific business tasks they support, they are ideal candidates for encapsulating in components that are physically separate from the application logic itself. For example, if a particular service required by an application is Get marked-up price, it makes sense to encapsulate this service in a component that resides on a central network server and is accessed by the application. Then, if the procedure for calculating the markup changes, it can be changed in a single location without altering the user portion of the application itself. Once the business service is changed, all requests to Get marked-up price will be answered with the new result from the modified business service component.