The viewID, a String field of the base ViewParameters object, identifies a View, or rather a class of views. A view is a page with a common appearance and set of components backing it - i.e. it is the viewID which is used as the primary key to look up the ViewTemplate and the ComponentProducers for the current render (GET) cycle. The other (application defined) members of ViewParameters may define the view behaviour in more detail, but they cannot affect this initial lookup process (using the default implementations of ViewTemplateLoader &c).