Exploratory Search Interfaces:
Categorization, Clustering and Beyond
Report on the XSI 2005 Workshop at the Human-Computer
Interaction Laboratory, University of Maryland
Ryen W. White1, Bill Kules2 and Ben Bederson1,2
Human-Computer Interaction Laboratory
1
Institute for Advanced Computer Studies
2
Department of Computer Science
University of MarylandCollege Park, MD 20742 USAAbstract
The development and testing of systems to support users engaged in exploratory search
activities (i.e., searches where the target may be undefined) is an challenge for the online
search community. In this article we report on a workshop on exploratory search issues
organized in conjunction with the University of Maryland Human-Computer Interaction
Laboratory’s Annual Symposium and Open House in June 2005. This workshop brought
together researchers from the fields of Information Seeking (IS), Information Retrieval(IR), Human-Computer Interaction (HCI) and Information Visualization (IV) for a crossdisciplinary exploration of these and other issues. Although originally intended to focus
on interfaces to support exploratory search the workshop blossomed into a rich discussionof not only interface issues, but also evaluation, the cognitive processes that underlie
information exploration and research methods.
Introduction
Although the Semantic Web is making new richer and more flexible kinds of Web-based
querying possible a burning question remains “Are current search technologies enough tomeet all user demands?”. The answer of course is yes and no. Search engines,
bibliographic databases and digital libraries provide adequate support for users whose
information needs are well-defined. However, they do not work well in situations whereusers lack the knowledge or contextual awareness to formulate queries or navigate
complex information spaces [2]. For example, what if you want to find something from adomain where you have a general interest but not specific knowledge? How would you
find classical music you might enjoy if you do not know what Beethoven or Berlioz
sounds like? What a Sonata is? The difference between Baroque or Romantic? What doyou type into Google? 1
In situations where information needs are vague or evolving users generally havedeveloped coping strategies to compensate [1,2,5]. For example, they submit a tentative
query that retrieves documents and browse from there, dependent solely on their ability to1

Example taken from http://www.mspace.fm, a site describing the mSpace exploratory search browser.

interpret contextual cues and navigate between documents. In short, they explore
available information, selectively seeking and passively obtaining cues about where nextsteps lie. The goal of information exploration is the refinement of a vague informationneed that leads, through interaction with information objects and information resources,
to a more thorough understanding of the problem. Searchers may benefit from interfacesthat provide additional support, for example by enabling grouping of results and/or
guided discovery processes [3,4,6]. Researchers from communities such as information
retrieval, user interface design, visualization and library sciences have been working forsome time on techniques to support such exploratory searches.
Exploratory searches are typified by uncertainty about the space being searched and thenature of the problem that motivates the search. People engage in exploratory searchingboth intentionally and incidentally to other activities. It includes situations where: (i) thetarget of the search is unknown or partially unknown, (ii) the search begins with somecertainty about what is known but changes into one unknown and unfamiliar on exposure
to new information and (iii) users recognize useful information objects by scanning
through information resources, evaluating their usefulness and determining thecontent/structure of a set of information objects. Relevance feedback (RF), and inparticular implicit relevance feedback, is a technique that complements users explorationof the search space and the reduction in uncertainty about the target of the search that canresult from this activity.
Domains such as the World Wide Web create tantalizing opportunities for learning andresearch, not only for students and researchers, but also for journalists, attorneys, andpractitioners in many fields. The growth in interest in technologies to search these
domains has meant that the problems associated with search have occupied center stage
in the computing community for some time. The broad nature and scope of these
problems meant that those within this community may benefit from the sharing ofexpertise that an inter-disciplinary workshop of this nature encourages.
Participation
The workshop brought together 36 researchers from academia, government and industry
for a cross-disciplinary exploration of issues about exploratory search. Everyone
contributed to a lively and engaging discussion that was well received by participants. A
strength of the workshop was the diversity of participant backgrounds and the variety ofperspectives on similar problems in a mixture of domains. The workshop demonstrated ahigh level of interest in this topic, so much so that we had to close registration early.
Participation was by invitation only. A number of presenters were selected prior to theworkshop based on the estimated contribution of their research to the diversity of theproceedings. Those presenting were asked to provide a one paragraph abstract for theirpresentation and their one paragraph definition of exploratory search. The abstracts wereused to arrange the speakers into topically-coherent groups. Presentations varied inlength from brief one minute introductions to twenty minute keynotes. We invited four
special guests to give keynote presentations:

••
•
•

Can Exploratory Search be Distinguished from Other Kinds of Information
Seeking Behaviors, and Can a Search Interface Support a Variety of SuchBehaviors? (Nicholas J. Belkin, Rutgers University)
Are there optimal ways to do exploratory searching?
(Marcia Bates, University of Southern California)
Search: Lessons learned from browsing movies and pictures(Steven Drucker, Microsoft Research)
Exploring Information Needs, Results Analysis, and Information Use(Susan Dumais, Microsoft Research)

The definitions of exploratory search provided by participants prior to the workshop wereused as part of a introductory “ice breaker”. As part of the introductory activity weplaced everyone’s definition of exploratory search in large font on a separate sheet ofpaper and pinned two sets of these definitions to the wall on opposite sides of the room.
We then divided the participants arbitrarily into two groups and asked them to rearrange
the definitions in a way that made that made sense to them. They were given a large
sheet of paper and asked to take notes on the reasons behind their decisions and any
emergent themes. Subjects clustered definitions in interesting ways and provided
interesting rationale for their decisions; a discussion of this is included in future work.
A workshop web site was created at http://umiacs.umd.edu/~ryen/xsi containing detailsof the program and the slides from all presentations.
The remainder of the day was divided into three oral presentation sessions broadlyclassified as “Seeking”, “Retrieval” and “Visualization”. The afternoon was devoted to a
discussion of themes defined by participants in a pre-discussion brainstorming session.
The themes that emerged were:
••
•
•
•

users needs (i.e., what support user wants; what feels good, natural or correct)
search strategies (i.e., how users search)tasks (i.e., what they are trying to accomplish)
evaluation measures (i.e., how to evaluate support offered)workspaces to support exploratory search (i.e., what help should systems offer)

We had originally planned for breakout sessions in the afternoon covering each of theseissues. However feedback from participants indicated a preference for a single discussion
involving all participants devoting time to each of these issues.
Some implications for interface design
The unique nature of searches where the target is unknown or undefined calls for new
interface designs that help users. Participants agreed that interfaces to support user
exploration are a vital (and missing) part of most current mainstream search technology.
Some emergent themes from the workshop were that exploratory search systems:

••••should use the context of user search activity and contextual information available
the target documents to aid user understanding and reduce uncertainty about thenature of the problem and the information being searched;need to be able to support a diverse range of user search strategies such as recall
and recognition, facet-based search and domain selection;
are problematic to evaluate and longitudinal, ethnographic and scenario-based
methodologies may be appropriate to test them, and;should contain “workspaces” to support a spectrum of activities, from
unstructured note-taking to integrated authoring environments.

The discussion notes from the workshop are available on the workshop website. A moredetailed analysis of the implications will be presented in future work.
Concluding remarks
Those attending the workshop reinforced the understanding that exploratory search is amulti-disciplinary problem that is troublesome to support at the interface and difficult toevaluate interfaces that do attempt to support it. Participants felt that not only wasaddressing the problem timely it was also crucial to help users and a fascinating
opportunity to extend current levels of understanding and apply well-established theory
to new contexts. Across the variety of disciplines where techniques to support
exploratory are studied there is a need to improve the contextual awareness of the user,
bring information that supports exploration to the fore and establish how the effectivenessof these systems can be determined.
Further activities that will help define the field are being considered. Perhaps the mostexciting is that as a result of the workshop, two of the authors of this article (Ryen Whiteand Bill Kules), alongside Steven Drucker (Microsoft Research) and m.c. schraefel(University of Southampton), are editing a special section of the Communications of theACM in April 2006 entitled “Supporting Exploratory Search”. The special issue will:•••bring exploratory search into the spotlight and reflect the cutting edge research
being conducted into this important problem
describe how exploratory search is handled in a variety of disciplines:
o combine theory and practice in each of the fields of interesto describe how these disciplines overlap and interacto demonstrate the value of interdisciplinary collaboration
propose evaluation methodologies and metrics for exploratory search interfaces

A further activity we are considering is the organization of a workshop on exploratory
search at future venues such as SIGCHI, SIGIR and ASIST. At these forums it is hopedthat we can attract large numbers of participants to continue the discussion of the issues
raised in this workshop.
The scope of search technologies must expand beyond known search targets to support
information exploration. It gave all of the organizers great pleasure to arrange thisworkshop and focus the minds of those interested in online search on this problem.

Acknowledgments
We are grateful to AOL for their financial support, to Doug Oard and Ben Shneiderman
for their invaluable comments and guidance, and Kiki Schneider for her administrativeassistance.
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