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2.9 Fisheye Views and Spiders

Furnas implemented a fisheye view algorithm which is similar to looking at a scene with a wide angle lens – things of greater interest will be at the center, while items of lesser interest will be on the periphery. This algorithm generates an image of the neighborhood by computing a relationship between a priori importance of a node and the distance between that node and the current position in the hypertext network [Carlson, 1989].

Thoth-II treats hypertext as a directed graph with semantics [Collier, 1987]. Nodes themselves do not contain text. Pieces of text are connected to the nodes by text links while the nodes are connected to each other by labeled value links; text can contain embedded links, called lexical links, to other nodes. “Spiders” is a directed graph browser in Thoth-II where a global map is created dynamically as a user browses through linked nodes. As the user interacts with the structure that is being viewed, new graphic objects (nodes and links) are created. Activating a node expands it showing links to other nodes which themselves fan out to other nodes. Thus, the network expands or fans out in two-dimensional space creating “spiders” on the display. The window on which this structure is displayed can be moved around to view other parts of it falling outside the viewing area. The browsing mode allows the user to browse through the graph and manipulate nodes and links whereas the text mode allows the user to view the textual pieces attached to the nodes. The disadvantage with this system is that the whole screen can get filled up with spiders very quickly as the user clicks on various nodes.