Course communication tool

To facilitate class communication (e.g., course announcements, Q&A) and logistics such as assignment submissions, the instructor created a private Slack team. Slack is a team communication tool first popularized by tech startups and more recently adopted by educators. Compared to a traditional threaded discussion format, Slack's key strength for fostering learner discourse is its free-flow style of communication. Specifically, instead of having students posting in a thread each week, the class created several Slack channels for different purposes. The linear progression of discourse in each channel helps participants stay current on the most recent posts, while they can easily revitalize an idea posted weeks earlier (Goal 2). In addition, various social features, such as mentioning a user and reacting to a post (with emojis), could benefit stronger social presence in this online course. 
Slack is not merely an alternative to discussion forums. Its support for file sharing and management enables students to share conceptual artifacts (e.g., an essay, a code snippet) flexibly to the whole class, a specific channel, or an individual. In addition, Slack's open API brings about a wide range of plugins that serves various purposes ranging from integrations with external tools (Hypothesis included), chat bots, to GIF importers. These possibilities, many of which were untapped in this design case, offers interoperability and personalization capabilities unseen in many LMS solutions \cite{Brown2015-wh}.
To support privacy and intimacy of formal course participants, the Slack team was set to private and not accessible to open participants (Goal 4). Students submitted course assignments in a dedicated 'assignments' channel and made their submissions visible to all Slack members. Such openness in the closed environment worked extremely well, as students started to share project ideas and codes and commented actively on each other's work. Moreover, the class' Hypothesis activities were synced with a dedicated Slack channel, thanks to Hypothesis' API, in a way that social annotations containing the course hashtag (made by formal or open participants) were notified on Slack as well (Goals 2, 3, 4). 
Table 1 summarizes how these three components are coming together to achieve the design goals, and Figure 2 illustrates course experiences and discourse processes supported by these components. The Bookdown course website served as a portal bringing various web objects into the class discourse and enabled two pathways of participation. Hypothesis supports interactions on various web objects (e.g., course textbook) in the form of web annotations, allows ideas shared in annotations being shared elsewhere, facilitates varied mechanisms to review and participate in the discourse, and promotes two participation pathways and boundary crossing between them. Slack provides a replacement of typical threaded discussion forums, but with stronger support for keeping tracking of ideas, revisiting earlier ideas, and repurposing ideas in ever-evolving discourse experiences. Slack also provides entry points to the discourse by integrating Hypothesis annotations and further supports internal public-private boundary crossing in the formal pathway.  Beyond these three main tools, a standalone gradebook was used to keep track of student grades, a feature commonly found in an LMS.