Drawing DAG's

• To: fritzen@dfki.uni-sb.de, cl-windows@mcc.com
• Subject: Drawing DAG's
• From: Scott McKay <SWM@stony-brook.scrc.symbolics.com>
• Date: Tue, 7 Sep 1993 11:16 -0400
• In-Reply-To: <9309071139.AA04516@winoserv-1.dfki.uni-sb.de>

    Date: Tue, 7 Sep 1993 07:39 EDT
    From: "Michael Fritzen" <fritzen@dfki.uni-sb.de>

    We want to develop a user interface for our terminological knowledge
    representation system (KRIS) in LISP. One of the main features of this
    system is to compute a hierarchy of concepts, the so-called concept
    hierarchy.

    When trying to display this hierarchy (which is a directed acyclic
    graph) using the GARNET program several problems occurred:
    The layout function seems to produce good output only for trees but
    not for dags. Especially links cross both nodes and other links.
    Furthermore, some of the nodes on one and the same level in the dag
    have been displayed on extremely different x-positions on the
    screen.

    Is there any possibility to draw dags such that these problems do
    not occur with other Common Lisp/X Interfaces?
 
CLIM 2.0 supports DAGs as well as trees, but the layout engine produces
output that (in my opinion) is only acceptable.  It is far from state of
the art on the aesthetics axis.

    Especially, we are interested in building up the dag
    incrementally, i.e., displaying one (or more stages) of the dag
    initially, and displaying further portions of the graph by
    mouse-clicks on displayed nodes.

Using CLIM's incremental redisplay facility in conjunction with its
grapher allows exactly such interactions.  The "graphical browser" demo
included in CLIM 2.0 does exactly this.

• Drawing DAG's
• From: "Michael Fritzen" <fritzen@dfki.uni-sb.de>

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