I've played around with some semantic net programs over the years. An outline is basically a tree structure, which is a (very limited) type of semantic network [1], which is itself a type of directed graph.

A classic outliner maintains a hierarchical information structure (MORE's ability to embed outline sections in multiple locations extended the hierarchy, but MORE did not have a hyperlink behavior).

In contrast to outliners, web based knowledge networks are very simple semantic networks (one type of one-directional arc); still they have interesting advantages over outlines. In an ideal world I would want to have structures that allowed me to move readily from an outliner world to the semantic network world (just as GrandView and "another unequalled 1980s product who's name I forget" blurred the distinction between database and outline) [2].

For those interested in such things, check out http://www.thebrain.com/ Quite interesting! Of course dangerous to actually use this tool to hold critical data -- I dread putting data into non-standard data structures -- still, fun to play with. You can make it act like an outliner, but it really wants to be a network (as designed).

john

[1] http://spuds.cpsc.ucalgary.ca/AIKM97/kuwata/kuwata97a.html
[2] I would love it if a mozilla team did a variation of Mozilla that treated the browser headings hiearchy as collapsible outliner headings -- assuming a well formed document.

You might wish to try Inspiration ver 6. (www.inspiration.com) It is an outliner & diagrammer.