History-aware user awareness in web lectures

User awareness has become a popular feature in many social web applications. In classic text-based web-systems, user awareness features show how many users are online in a web application or how many users are accessing the same web page. When time based media like web lectures are concerned this approach comes to its limits since time-based media are inherently different from classic text-based media. The main difference in these two types of media is that text-based media can easily be skimmed at a glance while video- or audio-objects have to be fully replayed when users want to grasp their content. This paper presents an approach that employs time-based usage statistics for all users in a web lecture system in order to provide users with a means to communicate with other users who are online and have watched those parts of a media object that the user is interested in. The work is implemented in the context of the Opencast Matterhorn project - an open source based pr oject for producing, managing and distributing academic video content.