Digital Sovereignty with email & calendars - Is the client the bottleneck?

<!--HTML-->Even super-humans have every hour of the day only once. To collaborate with teams a requirement is to have one calendar per person and to share its free/busy-information with team-members. (How) Is it possible to collaborate beyond the borders of the own organizations in a digital sovereign world with a colourful bouquet of different collaboration solutions? Hint: I do not trust in the ‘Ring that rules them all”. And the standard must not be a protocol. My talk is about the thing we call ' groupware' and we do mean e-mail, calendar, contacts and tasks by this. I am going to focus on calendars and will reflect on a history starting at MS Exchange 2000, following a path via MAPI, IMAP, CalDAV, ActiveSync-over-the-air, z-push, and completely bypassing MS Outlook. The view I am going to present is from a 3rd party integrations perspective as well as from an end-users perspective. Hereby I will touch the role of APIs to connect to standards to realize interoperability with other tools, even the ones outside your own organization. An example I will touch is the exchange of calendar availability.