daVinci is available for download and is licensed free of charge for non-profit use.

daVinci is an interactive tool to visualize directed graphs. A graph is a structure with a number of objects (nodes) and relationships between them (edges). For directed graphs, all edges have a direction, i.e. for each edge there is a parent- (the source) and a child node (the target). The graph layout in daVinci reflects these hierarchical relationships by arranging the nodes at horizontal levels such that all parent nodes are above their child nodes and all edges point downwards (in a top-down layout). Further, the direction of an edge is usually visualized with an arrow pointing to the child node. This kind of representation is called hierarchical visualization of a directed graph.

When there is a need to edit a graph by hand, users can connect an external graph editor application to do this interactively based on the visualization of a graph. The grapheditor is an external program that communicates with daVinci by using the API ( Application Programmer Interface). The editor (or any other daVinci application) is responsible for exclusively controlling and manipulating the structure of a graph. At start time, the editor adds some menus to daVinci's user interface, e.g. to insert or delete nodes and egdes or to change their attributes. Application menus are attached to the Edit menu, but there is no function behind these menus in daVinci. Instead, the API sends menu events to the graph editor to inform about interactions. For example, when the user selects a node (1. event) and chooses the previously attached menu 'Edit/Delete Node' (2. event), then the editor knows by these two events that the user would like to remove the specified node. The editor has its own graph data structure which needs to be modified by the editor to reflect the events. After modification, the editor will send the actual graph back to daVinci to update the visualization.

This principle can be used by any application program that is connected to daVinci's API. Note that the application is exclusively responsible for controlling the graph structure. daVinci is not able to modify the graph on its own. This is important when daVinci is the graph user interface on top of an arbitrary application program. On the other side, by separating the representation layer (daVinci) from the control layer (application connected to the API), the application programmer is relieved from dealing with graph layout algorithms and computer graphics, so he/she can concentrate on his/her true work.

GDPA Online Last Updated 01.Jan.2002 Updated by Webmaster Last Revised 01.Jan.2002 Revised by Webmaster