So we have three different cases for displaying facts to the user

1. user comes to the page for the first time
2. user selected some "compose" facts which means it have some parents
3. user used searchbox to find some facts

For the first one we must select roots only. For the second we must limit facts by their parents. The last is most tricky since user can pick a host for which he wants to see facts. This selected host is then converted (from params) to a search condition displayed in searchbox. However this condition can apply to 1.,2. and 3. and should not affect selection of display case. That's why we reject any condition that is related to hosts when decide what's current displaying case.