Each Pernosco view is an independent timeline of events. The current focus is visually highlighted within each view, and the events in a view are ordered by time from top to bottom, but there is no visual indication of the relative ordering of events in different views. Sometimes it would be useful to have a timeline showing the relative order of different kinds of events (e.g. garbage collector invocations and console output).
We overcome this limitation by allowing multiple views to be combined into a single view. Not all combinations are supported, but for those that are, users can merge views by simply dragging one into another. The new view contains the union of the events, all ordered by time.
This is a very simple "union" operator on views. One can imagine more complex operators, and even explicit query languages, but we don't have enough user experience to pursue that yet.