The original name of this effort was Display Sets reflecting the need for collections that are focused on grouping works for display to end users. As the working group efforts moved forward, it became clear that there was a broader set of use cases. In an effort to avoid having one-off implementations for each type of grouping of works for every new use case, the working group directed their efforts toward a generalized solution. The rename to Collection Extensions reflects the shift in focus to expanding the current code base used for user collections to accommodate the varied identified use cases. The core piece of this work is the creation of configurable collection types that allow sites to control their adoption of the various extension. See the documents in the working groups for more information and details.
Through out the documents of the working groups, you may see the groupings of works referred to as Display Sets, Collections, or Collections Extensions. This reflects the evolving understanding of the required work. The term being used going forward is Collection Extensions.
Slack channel: https://project-hydra.slack.com/messages/collection_extensions/ (NOTE: Renamed from display_sets.)
Due to the complex nature of extending collections and addressing their interactions with Admin Sets, there has been an extensive requirements and UI/UX design process that will be followed by implementation sprints. Each had a separately formed working group. The following are the pages for each working group.
Collection Extensions blog
More to come...