Stress-Minimizing Orthogonal Layout of Data Flow Diagrams with Ports - Graph Drawing - page 318

Stress-Minimizing Orthogonal Layout
of Data Flow Diagrams with Ports
Ulf Ruegg 1 , Steve Kieffer 2 ,
Tim Dwyer 2 , Kim Marriott 2 ,andMichaelWybrow 2
1 Department of Computer Science, Kiel University, Kiel, Germany
[e-mail]
2 Faculty of Information Technology, Monash University, NICTA Victoria, Australia
{ Steve.Kieffer,Tim.Dwyer,Kim.Marriott,Michael.Wybrow } @monash.edu
Abstract. We present a fundamentally different approach to orthogonal
layout of data flow diagrams with ports. This is based on extending con-
strained stress majorization to cater for ports and flow layout. Because
we are minimizing stress we are able to better display global structure, as
measured by several criteria such as stress, edge-length variance, and as-
pect ratio. Compared to the layered approach, our layouts tend to exhibit
symmetries, and eliminate inter-layer whitespace, making the diagrams
more compact.
Keywords: actor models, data flow diagrams, orthogonal routing,
layered layout, stress majorization, force-directed layout.
1 Introduction
Actor-oriented data flow diagrams are commonly used to model movement of
data between components in complex hardware and software systems [13]. They
are provided in many widely used modeling tools including LabVIEW (National
Instruments Corporation), Simulink (The MathWorks, Inc.), EHANDBOOK
(ETAS), SCADE (Esterel Technologies), and Ptolemy (UC Berkeley). Complex
systems are modeled graphically by composing actors , i. e., reusable block dia-
grams representing well-defined pieces of functionality. Actors can be nested —
i. e., composed of other actors—or atomic . Fig. 1a shows an example of a data
flow diagram with four nested actors. Data flow is shown by directed edges from
the source port where the data is constructed to the target port where the data
is consumed. By convention the edges are drawn orthogonally and the ports are
fixed in position on the actors' boundaries. Automatic layout of data flow di-
agrams is important: Klauske and Dziobek [12] found that without automatic
layout about 30 % of a modeler's time is spent manually arranging elements.
Current approaches to automatic layout of data flow diagram are modifica-
tions of the well-known Sugiyama layer-based layout algorithm [18] extended to
handle ports and orthogonal edges. In particular Schulze et al. [16] have spent
many years developing specialised layout algorithms that are used, for instance,
in the EHANDBOOK and Ptolemy tools. However, their approach has a number