1) @DataModelSelection injects; don't use @In for a context variable annotated with @DataModelSelection (also don't use @Out with @DataModel).
2) A manager component is any component with an @Unwrap method. This method returns the value
that will be visable to clients, and is called every time a context variable is referenced.
3) You could possibly use scope=ScopeType.EVENT scope (which is shorter duration than PAGE, it's effectively REQUEST scope), but not sure if that is allowed or not with @DataModel or @Out