DS is an ability to add or change sharing during operation of an application, either in response to changing requirements, or from a participant's command. For example, a task force evaluating earthquake protection may bring a materials specialist into the process for specific data or computation, and then detach his connection when done while the task force continues to work. Single authentication means that you identify yourself once, and that authorization is automatically forwarded where needed. This capability exists within a single network entity of trusted systems and users, but the SA capability is capable of global authorization from a single login. Thus, across geographic and organization boundaries, your authentication enables automatic access to all functions that you are entitled to access.
Virtual collaborations are a major result of a grid.
A VC can exist for an hour, a week, or several years. Most often it will involve groups of specialists pooling their knowledge, data, and software to solve a specific problem. During its existence, the collaborators will share limited amounts of their knowledge under specific security and sharing rules, accessing agreed data and software and interpreted by the domain experts. When it is finished the results are delivered and the VC disappears until the next time it is needed, perhaps then with other participants.