1. Alice invites Bob to join her team by entering his email address and an optional invitation message.
2. System sends Bob an email containing an invitation link to join Alice's team.
3. Bob clicks on the invitation link.
4. Bob reaches a registration/sign in page and creates his new Synapse account.
5. System adds Bob's account to Alice's team.

1. The email addresses entered by Alice doesn't exist.

1. 1. System sends an email to Alice to notify her of the problem.
   2. Alice tries again with a different email address.

2. System detects that the email address entered already has a Synapse account associated with it, presumably it's Bob's account.

1. 1. System sends Bob a membership invitation to Alice's team.
   2. Bob accepts the invitation and joins Alice's team.

3. Alice decides not to collaborate with Bob anymore and wants to cancel her invitation.

1. 1. Alice navigates to her team's page and clicks on the remove button associated with the pending invitation to Bob.
   2. System invalidates the invitation link sent to Bob.
      1. The link Bob received is no longer valid and directs to an error page.

4a. Bob already has a Synapse account associated with a different email address and is already signed in in his browser.

1. 1. System adds Bob's account to Alice's team.

4b. Bob already has a Synapse account associated with a different email address but isn't signed in.

1. 1. Bob clicks on "Sign in" and signs in with his existing account.
   2. System adds Bob's account to Alice's team.

5. Bob clicked on the invitation link a long time* after it was issued. (* definition of long time to be specified)

1. 1. System sends a membership request to Alice's team instead of directly adding Bob to Alice's team.