A contemporary approach to describing and theorizing about joint human endeavor is to posit 'knowledge in common' as a basis for awareness and coordination. Recent analysis has identified weaknesses in this approach even as it is typically employed in relatively simple task contexts. We suggest that in realistically complex circumstances, people share activities and not merely concepts. We describe a framework for understanding joint endeavor in terms of four facets of activity awareness: common ground, communities of practice, social capital, and human development. We illustrate the sort of analysis we favor with a scenario from emergency management, and consider implications and future directions for system design and empirical methods. q

To improve existing social bookmarking systems and to design new ones, researchers and practitioners need to understand how to evaluate tagging behavior. In this paper, we analyze over two years of data from CiteULike, a social bookmarking system for tagging academic papers. We propose six tag metrics-tag growth, tag reuse, tag non-obviousness, tag discrimination, tag frequency, and tag patterns-to understand the characteristics of a social bookmarking system. Using these metrics, we suggest possible design heuristics to implement a social bookmarking system for CiteSeer, a popular online scholarly digital library for computer science. We believe that these metrics and design heuristics can be applied to social bookmarking systems in other domains.

We study the development of common ground in an emergency management planning task. Twelve three-person multi-role teams performed the task with a paper prototype in a controlled setting; each team completed three versions of the task. We use converging measures to document the development of common ground in the teams and present an in-depth analysis of the characteristics of the common ground development process. Our findings indicate that in complex collaborative work, process common ground increases, thus diminishing the need for acts like information querying or strategy discussions about how to organize the collaborative activities. However, content common ground is created and tested throughout the three runs; in fact dialogue acts used to clarify this content increase over time. Discussion of the implications of these findings for the theory of common ground and the design of collaborative systems follows.

How much instructional assistance to provide to students as they learn, and what kind of assistance to provide, is a much-debated problem in research on learning and instruction. This study presents two multi-session classroom experiments in the domain of chemistry, comparing the effectiveness and efficiency of three highassistance (worked examples, tutored problems, and erroneous examples) and one low-assistance (untutored problem solving) instructional approach, with error feedback consisting of either elaborate worked examples (Experiment 1) or basic correctness feedback (Experiment 2). Neither experiment showed differences in learning outcomes among conditions, but both showed clear efficiency benefits of worked example study: equal levels of test performance were achieved with significantly less investment of time and effort during learning. Interestingly for both theory and practice, the time efficiency benefit was very substantial: worked example study required 46-68% less time in Experiment 1 and 48-69% in Experiment 2 than the other instructional approaches.

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