Defining, Designing and Evaluating Social Navigation Martin Svensson A Dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy Stockholm University Department of Computer and Systems Sciences December 2002 Department of Computer and Systems Sciences Stockholm University Human Machine Interaction and Language Royal Institute of Technology Engineering Laboratory, Kista Report series No. 03-001 SICS Dissertation Series 33 ISSN 1101-8526 ISSN 1101-1335 ISRN SU-KTH/DSV/R--03/1—SE ISRN SICS-D--333--SE ISBN 91-7265-573-9 Doctoral thesis Department of Computer and Systems Sciences Stockholm University Copyright © Martin Svensson, 2003. ISBN 91-7265-573-9 This thesis was typeset in Garamond 12pt using Microsoft Word 2000, Adobe Illustrator 9, and Adobe Photoshop 5. Printed by Akademitryck AB, Edsbruk, Sweden, 2003. Till Karin Ekberg I Abstract The issue of how users can navigate their way through large informa- tion spaces is crucial to the ever expanding and interlinking of com- puter systems. Computer users live in a world of information spaces but in many situations lack the necessary means to navigate them. To meet this increasing need for navigational support social navigation has been proposed as a possible solution. The term captures every-day be- havior used to find information, people, and places – namely by watch- ing, following, and talking to people. This thesis sets out to investigate social navigation from three different perspectives: how it can be de- fined, how it can be designed, and how it can be evaluated. By examining the properties of information spaces and navigation we define social navigation as navigation that is driven by the actions of others. Actions can by communication in several ways, and specifically, we make the distinction between direct and indirect social navigation. Based on our understanding of social navigation five design principles for social navigation are proposed: presence, privacy, trust, integration, and appropriateness. They are issues that have to be considered when designing systems that support social navigation. The Social Navigator toolkit enables designers to in domain-relevant ways, instantiate and re- alize these design principles in their systems. To test the social navigation design principles two socially enhanced food recommender systems were created. The first, EFOL, was evalu- ated in a small-scale study to verify that the Social Navigator worked. The second system, Kalas, was used to evaluate the benefits and prob- lems with social navigation. In a study that ran over a six-month period Kalas was evaluated. The results partly indicate that social navigation adds quality to a system, that social navigation works well with other navigational aids, and that recommender systems need not be boot- strapped. III Acknowledgement I want to mention the following people (in no particular order): My advisors: Kristina and Calle. For comments: Kristina, Rickard, Adrian, Åsa, and Jarmo. For believing in the work: Kristina. For support: Rickard, Kristina, and Anna. For putting up with me: Anna, Agneta, Bosse, Hasse, Thor, Christian, Niklas, Alex, Johan, and Rickard. For Kalas: Gerd, Anna S, Kristina, and Rickard Contents V Contents 1 Introduction....................................................................................... 1 1.1 Research challenge.....................................................................................1 1.1.1 Defining social navigation....................................................................2 1.1.2 Designing social navigation..................................................................3 1.1.3 Evaluating social navigation.................................................................3 1.2 Methodological outline..............................................................................5 1.3 Contributions..............................................................................................5 1.4 Publications and co-operation..................................................................6 1.4.1 Reading instructions..............................................................................7 2 Defining social navigation.................................................................9 2.1 Information spaces ....................................................................................9 2.1.1 Environmental knowledge .................................................................11 2.1.2 Properties of space ..............................................................................11 2.2 Navigation.................................................................................................14 2.2.1 Type of navigation...............................................................................16 2.2.2 Navigational aids..................................................................................18 2.3 Social navigation.......................................................................................18 2.3.1 Defining social navigation..................................................................19 2.3.2 Direct social navigation ......................................................................21 2.3.3 Indirect social navigation....................................................................27 2.4 Comparing social navigation to other activities...................................33 3 Designing a general tool for social navigation................................ 37 3.1 Social navigation and implications for design......................................37 3.2 Design principles for social navigation.................................................38 3.2.1 Presence and awareness......................................................................38 3.2.2 Trust in the advice provider...............................................................39 3.2.3 Privacy for the advice provider .........................................................40 3.2.4 Appropriateness...................................................................................40 3.2.5 Integration ............................................................................................41 3.3 The proposed solution ............................................................................41 3.3.1 Architectural overview........................................................................45 VI Contents 3.4 The Social Navigator............................................................................... 45 3.4.1 Web server ........................................................................................... 48 3.5 Navigator .................................................................................................. 48 3.5.1 Initialization ......................................................................................... 49 3.5.2 Containers ............................................................................................ 50 3.5.3 Supporting indirect social navigation............................................... 50 3.5.4 Supporting direct social navigation .................................................. 54 3.6 Social Navigator servlet .......................................................................... 55 3.6.1 Sessions................................................................................................. 55 3.6.2 Communication with the client......................................................... 56 3.7 Collaborative and content based filtering ............................................ 57 3.8 Default java client.................................................................................... 59 3.9 A Comparison with MetaWeb and WebPlaces................................... 63 3.9.1 WebPlaces ............................................................................................ 63 3.9.2 MetaWeb .............................................................................................. 65 3.9.3 Social Navigator versus WebPlaces and MetaWeb........................ 67 4 Designing social navigation systems for the food recipe domain ..................................................................69 4.1 Online food shopping............................................................................. 69 4.2 Designing EFOL ..................................................................................... 71 4.2.1 A design principles walkthrough ...................................................... 73 4.2.2 Indirect social navigation in EFOL.................................................. 74 4.2.3 Direct social navigation in EFOL .................................................... 75 4.3 Implementation........................................................................................ 76 4.4 A first evaluation of the online store.................................................... 77 4.4.1 Subjects................................................................................................. 78 4.4.2 Task and procedure ............................................................................ 78 4.4.3 Results................................................................................................... 78 4.4.4 Different users different concerns.................................................... 78 4.4.5 Social affordance................................................................................. 80 4.4.6 Social experience ................................................................................