Visualization of Navigation

WebMap is intended to extend the capabilities of common WWW clients like Mosaic[15] or [17]. Therefore, WebMap has to be notified by such a client about the documents the client accesses. Additionally, it must be able to tell the client to load a particular document (see section 3.3 for a description of the interaction between WebMap and Mosaic).

During the user's hyperspace travel WebMap creates and updates a topology representation of the navigation history. This internal representation reflects the structure of the hypertext, i.e., the relation between all documents the user has visited so far. In this context the web resulting from the complete history is viewed as a graph whose nodes correspond to WWW documents and edges to hyperlinks resp. direct URL jumps, i.e., manual URL input by the user.

WebMap maintains the topology information by calculating a so-called spanning tree. The construction of a spanning tree divides the set of edges roughly into two categories:

• Tree-edges: All edges of the spanning tree.
• Non-tree-edges: All remaining edges of the graph.

This construction is done essentially in the following manner:

• If a document is accessed for the first time, a new topology node is created and connected with its predecessor through a tree-edge.
• Otherwise, if the document has been visited before with a different access path, a non-tree-edge is created to connect the node with its predecessor.

• Example
• Layout strategies
• Tree layout algorithm
• Horizon Tree