What if the PID service is down?

If the PIDs cannot be resolved at a certain moment one simply cannot access a resource. Think of a situation where hundreds of users are waiting on a resolution of a and nothing happens - a nightmare for any cyberinfrastructure scenario! Since this would not be acceptable, we need to make sure that the PID service is based (a) on a very robust and reliable software offering sufficient functionality, (b) on a proper service based on redundant centres with a high availability and persistency guarantee.