Interactive Navigation of Large Graphs and Networks Tamara Munzner Stanford University Graphics Group, CS Dept

Overview zCognitive psychology wish list zInfoVis problems zGraph drawing examples ygraph == network ynode-link as in graph theory ynot bar charts

Interaction zFluid interaction is hallmark of modern CG zCan create non-real environments zExample: navigation yRW: rigid motion across fixed terrain yCG: distortion, warping of structure/space xwhen (if ever) is this useful?

Wanted: Prescriptive Advice zHave for static 2D yGestalt, Bertin, Mackinlay, etc zMy wish list: ydynamic, spatial xwhen are distortion (focus+context) systems useful?

Process z[Distill domain knowledge into explicit problem statement] zFind visual technique(s) to help solve problem with preattentive processing zFeedback: is system solving problem? yAre they using it? yDoes it help?

CP wish list, cont. zAnalyze what’s good when: yTease apart complex visual metaphors into constituent low-level components yConceptual framework, user studies zBackmapping: once know what it’s good for, what other domains can be abstracted into this problem?

Problems zScalability yreal-world datasets consistently outstrip tools zEfficacy ylack of rigor in evaluating viz systems zNovelty ycreating new visual metaphors is difficult zAdoption yend user buy-in

Graph drawing: traditional zStatic++ yinteractivity not inherent ypan/scroll/zoom substitute for really big paper zDoes not scale ysmall (dozens, hundreds, maybe thousands) yaggregation/abstraction of large datasets xgreat for expository, poor for exploratory zspring-force, circular, hierarchical, etc ydot, daVinci, Tom Sawyer, etc

Three Interactive Systems zGeographic: Planet Multicast zHyperbolic: H3/H3Viewer zImportance gradient: Constellation

Geographic: Planet Multicast zTarget users: Mbone maintainers zTechnique: arcs on globe [Eick95] zTask: identify long-haul misconfigurations

Planet Multicast excerpt zInteraction techniques: yclick on arc for tunnel info yrotate globe around center x selective occlusion yrotate around point on surface xhorizon view disambiguates

PM analysis zVisual popout: ylong-distance links ycluttered tunnel topology zLiteral & natural: no explanations needed zFiltering: intercity not intracity y4000 -> 700 yhemisphere occlusion

PM efficacy zgeog distance only approximates bottleneck sources yideal data uncollectable yfew false positives, many false negatives zIP address -> lat/lon mapping infeasible zAdoption: ymaintainer coauthor during development zDoes it help? yAnecdotal

Hyperbolic: H3Viewer zTarget users: webmasters, gawkers zTechnique: yuses 3D hyperbolic space for recursive hemispherical layout and navigation yspanning tree backbone with nontree links drawn on demand yguaranteed frame rate drawing algorithm zTask: show context of surfing choices

H3Viewer video

H3 analysis zVisual popout: ysubtree clusters zFiltering: yspanning tree in default case zScalability: y>100,000 nodes

H3 Efficacy zAdoption: yShips with SGI Irix xminor user testing xuser feedback in the wild extremely minimal yPD code, other developers xnetworking, genetic algorithms zDoes it help? yReal user study prelim results promising

Importance Gradient: Constellation zTarget users: two linguists at MSR zTechniques: ycustom spatial layout, horiz gradient ycareful use of HSV to minimize clutter impact zTask: debug semantic network creation yfind implausible computed paths

Constellation video

Constellation analysis zVisual popout: yhotspots, highlighted structures zFiltering: none ydesign principle of avoiding hidden state zAdoption: TBD ystill under development ypros and cons of tiny user community

Conclusion zKey problem in the field: yEvaluating efficacy yScalability zExploration of the design space ythree quite different GD systems

Acknowledgements zPlanet Multicast: yEric Hoffman, Kim Claffy, Bill Fenner zSite Manager: yGreg Ferguson, Alan Braverman, Ken Kershner zConstellation: yFrancois Guimbretiere, George Robertson zAdvisor: Pat Hanrahan

More info zhttp://graphics.stanford.edu/~munzner ypapers ytalks ysoftware