In ClearCase you can implement several different degrees of isolation from you colleagues. The 'tools' that implements the isolation are:
The expression that a view is "on" a branch (or a stream in UCM as the expression goes in UCM, despite the fact that technically it's the branch that is interesting) means that this it the branch that will hold new versions of elements created in this view.
So when an element is checked out, a new version is created, and the element is made writable in the view - it has become view private. It can then only be seen from that particular view and is thus isolated.
Dynamic views are then 1st degree of isolation. Since they are dynamic, new versions created on the branch will sort of "pop up" in other views automatically as soon as the version are checked in.
Snapshot views are then the 2nd degree of isolation because in this type of view, then new version are not automatically loaded into other views upon checkin. The new version remains isolated from oter views until the explicitly do an update of the view.
Branches (or streams as you would say in UCM) then make up the 3rd degree of isolation. New version on a stream or a branch will have to be merged, delivered or rebased, in order for these changes to show up in other branches.