Looking at computer support for collaborative learning (CSCL) in terms of (a) collaborative knowledge building, (b) group and personal perspectives, (c) mediation by artifacts and (d) micro-analysis of conversation provides a rich, multi-dimensional starting point for conceptualizing and studying CSCL. The notion of collaborative knowledge building defines a useful paradigm for conceptualizing learning as social practice. The social interactions and knowledge management activities in which shared knowledge is constructed can be analyzed as the result of interweaving group and personal conversational perspectives. In general, collaborative interaction is mediated by artifacts: sometimes only by transitory artifacts like spoken words or gestures, but increasingly by physical or digital artifacts and media. Empirical studies of collaborative knowledge building employing micro-ethnographic analysis of speech, gesture, artifacts and media can make the details of these collaboration interactions visible, highlighting the interplay of perspectives and artifacts in the trans-personal construction of knowledge. A theoretical framework incorporating models of knowledge building, perspectives and artifacts – and grounded in empirical analysis of collaborative interaction - can guide the design of computer-based artifacts and media as support for collaborative learning with appropriate, elaborated and unified conceptualizations.