MSO and multiple communities

[Dave Morris]

Guy Rixon wrote:

>Should communities, therefore, have a harvesting arrangement for user
>identities like the resource registry, such that every community knows about
>every user identity and knows the community where that identity originated?
>  
>
No need for a harvest, all you need to know is where to lookup the 
information you want.

This is one of the reasons why AstroGrid has the Community ident as part 
of the Account ident.
eg
    ivo://ast.cam.ac.uk/community
is the ivo identifier for a registered Community service
    ivo://ast.cam.ac.uk/community#dave
is the identifier for an Account in that Community.

If you want to check the certificates or group membership for
    ivo://ast.cam.ac.uk/community#dave
ask the Community service at
    ivo://ast.cam.ac.uk/community

It also solves the globally unique naming problem, 'dave' is not unique, 
but add the community identifier and 
'ivo://ast.cam.ac.uk/community#dave' is a globally unique identifier. 
Each community service can manage the names within its space, without 
having to check the whole Vo for conflicting names.

The group membership information does not need to be globally replicated.
If you are registered with the Community at Cambridge, then the 
Cambridge Community service can keep a list of groups you are a member of.
If you are added to a Group at Leicester, then the Leicester Community 
keeps the 'authoritative' record of this, but it can call the Cambridge 
Community to update your membership list.

Dave