Web 2.0 gives people a substantial role in content and metadata creation. New interpersonal connections are formed and existing connections become evident through Web 2.0 services. This newly created social network (SN) spans across multiple services and aggregating it could bring great value. In this work we present SONAR, an API for gathering and sharing SN information. We give a detailed description of SONAR, demonstrate its potential value through user scenarios, and show results from experiments we conducted with a SONAR-based social networking application. These suggest that aggregating SN information across diverse data sources enriches the SN picture and makes it more complete and useful for the end user.

The CSCW conference is celebrating its 20th birthday. This is a perfect time to analyze the coherence of the field, to examine whether it has a solid core or sub-communities, and to identify various patterns of its development. In this paper we analyze the structure of the CSCW conference using structural analysis of the citation graph of CSCW and related publications. We identify the conference's core and most prominent clusters. We also define a measure to identify chasm-papers, namely papers cited significantly more outside the conference than within, and analyze such papers.

We initiate the study of a new clustering framework, called cluster ranking. Rather than simply partitioning a network into clusters, a cluster ranking algorithm also orders the clusters by their strength. To this end, we introduce a novel strength measure for clusters - the integrated cohesion - which is applicable to arbitrary weighted networks. We then present C-Rank: a new cluster ranking algorithm. Given a network with arbitrary pairwise similarity weights, C-Rank creates a list of overlapping clusters and ranks them by their integrated cohesion. We provide extensive theoretical and empirical analysis of C-Rank and show that it is likely to have high precision and recall. Our experiments focus on mining mailbox networks. A mailbox network is an egocentric social network, consisting of contacts with whom an individual exchanges email. Ties among contacts are represented by the frequency of their co-occurrence on message headers. C-Rank is well suited to mine such networks, since they are abundant with overlapping communities of highly variable strengths. We demonstrate the effectiveness of C-Rank on the Enron data set, consisting of 130 mailbox networks.

The asymmetry of activity in virtual communities is of great interest. While participation in the activities of virtual communities is crucial for a community's survival and development, many people prefer lurking, that is passive attention over active participation. Lurking can be measured and perhaps affected by both dispositional and situational variables. This work investigates the concept of cultural capital as situational antecedent of lurking and de-lurking (the decision to start posting after a certain amount of lurking time). Cultural capital is defined as the knowledge that enables an individual to interpret various cultural codes. The main hypothesis states that a user's cultural capital affects her level of activity in a community and her decision to de-lurk and cease to exist in very active communities because of information overload. This hypothesis is analyzed by mathematically defining a social communication network (SCN) of activities in authenticated discussion forums. We validate this model by examining the SCN using data collected in a sample of 636 online forums in Open University in Israel and 2 work based communities from IBM. The hypotheses verified here make it clear that fostering receptive participation may be as important and constructive as encouraging active contributions in online communities.

While virtual communities become more and more dominant, little attention has been directed towards understanding the conditions for creating a successful community. Significant progress has been made in understanding the diffusion of collaborative tools in the workplace. We read stories about the extraordinary success of some communities, and about the harsh failure of others. This paper argues that lessons learnt from these stories should be analyzed using the theoretical foundations of Diffusion of Innovations theories, and systematized to create a set of guidelines for community creators to make their efforts more efficient. We begin by presenting a theoretical background for analyzing technology diffusion. We then analyze the stories of diffusion of ReachOut - a tool for peer support and community building developed in our Research Lab - in two different communities, using this theory. Finally, we propose a framework for planning for successful diffusion of collaborative tools, using our experiences with ReachOut.

Collaboration plays a vital role in today's new business environment. Knowledge that resides within people's heads has become an invaluable resource. Many formal tools, such as e-mail or teamrooms, have been introduced to support formal collaboration and have been studied extensively. However, support for informal communication is still in its infancy. Much work has been done to analyze the functions that informal communication plays in the workplace. Recently, several studies have evaluated the roles that instant messaging (IM) plays in similar settings. Research shows that in the workplace, IM is used primarily for work-related purposes and accelerates the completion of important business tasks. Clearly, new tools that combine both formal and informal interaction can bring organizations tremendous rewards. ReachOut is a tool for semi-persistent collaboration and peer support developed by the Collaboration Technologies Group at the IBM Haifa Research Lab. This paper studies the role ReachOut plays in the workplace. We analyzed the collaboration activity of the community of IBM Haifa Labs employees who used ReachOut for a period of two months. As a result, we summarize the important functions played by tools that bridge between formal and informal communication in a workplace-based community.

This paper presents ReachOut, a chat-based tool for peer support, collaboration, and community building. We describe the philosophy behind the tool and explain how posting questions in the open directly benefits the creation, distribution, and use of organizational knowledge, in addition to enhancing the cohesion of the community involved. ReachOut proposes new methods of handling problems that include locating, selecting, and approaching the right set of potential advisers. We discuss the advantages of public discussions over private, one-on-one sessions, and how this is enhanced by our unique combination of synchronous and asynchronous communication. We present and analyze results from a pilot of ReachOut and conclude with plans for future research and development.