A Type Library contains definitions for a COM object's methods and properties. When a COM object provides a Type Library, ABL references it before dispatching the method or property in an attempt to convert each method parameter or property value to the required COM data type. If a Type Library is available, ABL tries to match the number and types of any parameters being passed into a method before dispatching the method to the COM object for execution.

If both data-type specifier options and Type Library definitions are provided, the data-type specifier options take precedence. For more information on how OpenEdge matches ABL data items to COM object properties and method parameters, see COMObject Data Type Mapping.

You can locate data type information that is stored in Type Libraries on-line using the OpenEdge COM Object Viewer. For more information on Type Libraries and how to view their components, see Locating COM object information on your system.