A Data Object interface is an annotated ABL resource (a class file or a procedure file). The ABL resource must be a single class file or an external procedure that can be implemented as a singleton1 object.

If you have existing ABL resources, you annotate them using the Define Service Interface wizard.

If you want to create a Data Object interface from scratch, you must use the New Business Entity wizard and then add code to the class file that is generated. You can also use the New Business Entity wizard to quickly create a Data Object interface from a database table. OpenEdge automatically generates fully functional operations for the selected database table.

Note: You can only create class files using the New Business Entity wizard. If you want to use a procedure, you must create a procedure and annotate it using the Define Service Interface wizard.
1 A singleton resource is a class or external procedure that once instantiated is shared by all consumers of the class or procedure. ABL classes are inherently coded to be instantiated as singletons. However, an external procedure must not contain DEFINE PARAMETER statements in the main block to be instantiated as a singleton. An external procedure can contain internal procedures and user-defined functions with their own parameters, each of which can implement a Data Object operation.