Users can share specific parts of their Sovereign Silo with nominated trusted parties.
This 'access' is actually a seperate silo, specific to this trusted party's needs. There is no 'shared access' to user's own Sovereign Silo. Nope. That wouldn't be very Sovereign. Only SS does this.
Creating 'shared access' is how old database systems arbitrate third party access. Lots goes wrong. Lots.