Exploration of Networks using overview+detail with Constraint-based cooperative layout

Abstract

Abstract-A standard approach to large network visualization is to provide an overview of the network and a detailed view of a small component of the graph centred around a focal node. The user explores the network by changing the focal node in the detailed view or by changing the level of detail of a node or cluster. For scalability, fast force-based layout algorithms are used for the overview and the detailed view. However, using the same layout algorithm in both views is problematic since layout for the detailed view has different requirements to that in the overview. Here we present a model in which constrained graph layout algorithms are used for layout in the detailed view. This means the detailed view has high-quality layout including sophisticated edge routing and is customisable by the user who can add placement constraints on the layout. Scalability is still ensured since the slower layout techniques are only applied to the small subgraph shown in the detailed view. The main technical innovations are techniques to ensure that the overview and detailed view remain synchronized, and modifying constrained graph layout algorithms to support smooth, stable layout. The key innovation supporting stability are new dynamic graph layout algorithms that preserve the topology or structure of the network when the user changes the focus node or the level of detail by in situ semantic zooming. We have built a prototype tool and demonstrate its use in two application domains, UML class diagrams and biological networks.

Dunnart: A Constraint-Based Network Diagram Authoring Tool

“…It uses a recent algorithm for topology preserving constrained graph layout [7] designed for dynamic graph layout. This has previously been used for interactive visualisation of large networks [6]. Here we demonstrate its usefulness in a new application area: authoring.…”

Layout with Circular and Other Non-linear Constraints Using Procrustes Projection

“…We have had success using the adaptive trust-region step-size selection method proposed by Hu [15]. Though more costly, optimum step-size selection or Armijo Rules [3] could also be used to guarantee strict improvement as in [8].…”

“…This could equally well be an unconstrained iteration of the p-stress minimization method described in [8] or an iteration of any "force"-based approach. In our experiments we use a Fast-Multipole method following Lauther [17] so that ComputeDescentDirection completes in O(|V | log |V | + |E|) time.…”

“…For example, a diagram authoring tool [11] and on-line exploration of large graphs [8]. To achieve interactive responsiveness in such applications the projection step needs to be efficient and for certain classes of constraints we have been able to find methods of projection that compare favourably in running time to the basic unconstrained layout.…”

Topology Preserving Constrained Graph Layout

“…The first is a network diagram authoring tool, Dunnart, which uses the algorithm to provide continuous layout adjustment during user interaction [5]. The second is a network diagram browser which uses the algorithm to update the layout of a detailed view of part of the network as the user changes the focus node or collapses or expands node clusters [6]. The contribution of this paper is to detail the algorithm.…”