1. A method for generating a user interface using a modeling system, comprising: providing an editor for designing a visual representation of a user interface from a server system to a client system, the editor providing a workspace and a task panel to be displayed on a display device on the client system, the workspace being provided to design the visual representation thereon, the task panel providing a plurality of elements for use in designing the visual representation, one or more of the elements being associated with the server system remotely located from the client system; displaying a scenario selected by a user on the workspace, the scenario being compatible with user requirements for the user interface, the scenario including a plurality of interleaved scenes; defining each of the plurality of interleaved scenes according to inputs received from the user, each scene including concurrently active and collaborating actors, the actors being specialized computational units that represent threads of activities, where each scene is defined by diagrammatically defining a relationship between the actors associated with that scene; generating a canonic representation of a model represented by the scenario and the scenes; and generating executable user interface code of from the canonic representation.