1. A method for modeling a workflow, said workflow including activities, said workflow modeling a business process, said method comprising: displaying a plurality of activities on a display of a computer system, said plurality of activities being stored in a memory of the computer system; receiving a selection of the activities from a user via a user interface selection device of the computer system, said received selection of the activities to be included in the workflow; displaying the received selection of activities on the display; receiving from the user via the user interface selection device structure information for the selection of activities, said received structure information to be used to form the workflow; receiving a user-defined activity from the user via the user interface selection device, said user-defined activity having one or more semantics associated therewith; evaluating the semantics for conformance to a predefined interface requirement; displaying the received user-defined activity on the display as one of the plurality of activities as a function of said evaluating; receiving business logic from the user via the user interface selection device for association with one or more activities in the selection of activities; arranging the displayed selection of activities on the display in accordance with the received structure information and the business logic associated with the activities in the selection of activities to create the workflow for execution by the computer system; translating the created workflow into a user-designated language by the computer system in response to receiving a command from the user via the user interface selection device; and executing the user-designed language of the translated workflow by the computer system.