Drobs: Taking the Drag out of ‘drag ‘n Drop’ Web Pages 2. Drobs

graphics user interfaces in hypertext systems has been understood prior to the existence of the World Wide Web [6]. The current trend towards 'drag and drop' on a web page reflects the need for a level of interaction expected in other user interfaces. 'Drag and drop' can be achieved on web pages with a number of technologies [1][2][3][5]. These use different mechanisms based on an underlying pattern; first an event is generated indicating that dragging has started, events are generated while dragging proceeds, finally an event is generated when dragging stops, at the drop. A transfer operation implemented by the 'drag and drop' usually happens at the drop. While dragging, position and layout adjustments can also be made to the interface. How and where the dragging happens depends on the technology. In [1], for example, drag and drop is implemented by deriving objects from at least three classes: DragGestureListener, DragSourceListener and DropTargetListener. In Drobs ('DRaggable' OBjectS), development of 'drag and drop' interaction is undertaken by providing the maximum 'degrees of movement' for a draggable object. The idea that an aspect of a user interface can be described in terms of degrees of movement of components or data is not necessarily a new idea [8]. ABSTRACT 'Drag and drop' interaction on web pages can be achieved using a number of technologies, for example: Flash or Java embedded on the web page, and DHTML. In Drobs ('DRaggable' OBjectS), development of 'drag and drop' interaction is undertaken by providing the maximum " degrees of movement " for a draggable object. Adding constraints on the 'degrees of movement' then refines interaction. This approach is described using the development of 'drag and drop' into a scrolling window on a web page as an example. A version of a Drobs object library in DHTML is presented.