Knarr runs on an associative data engine, which allows for complex filtering of data including the ability to select fields, invert those selections, select alternative values, select possible values, and select excluded values. This capability allows you to traverse data extremely rapidly.
At first, selection states can be a little confusing, but once you click around and experiment with how they work, you will become an expert in no time.
There are a couple of ways to access the selection states. The first and simplest way is to use the buttons at the bottom of each filter, which perform, in order from left-to-right, "Select Possible", "Select Alternative", and "Select Excluded"
Right-clicking on any filter brings up a few more options that also allow you to clear the field or clear all other fields, or "Select All" values.
This selects all field values in a field regardless of the other selections made, Alternative values change state to selected (green). Excluded values change state to "selected excluded", which means they are still excluded from the current context, but if you clear the filters that made these values excluded, they will become selected values.
This selects all the currently possible values in a given field based on other filters made. This differs from "Select All" in that only the currently possible field values will become a selection, not all of the field values, which means that when you clear other fields, your selections in the "Select Possible" field will remain the same.
Try this out by filtering one field, choosing "Select Possible" in another field, then clearing your first field. Now try the same with "Select All". See the difference?
When a selection has already been made in a field, alternative values are values that would have been possible values if a selection had not already been made in that field. The simplest way to show this is to filter one field, then filter a few values in another field. On the second field, click "Select Alternative". Now click "Select Alternative" again.
By selecting alternative values, the values that previously were selected become alternative.
This selects all values that are excluded by your current selections. This behavior is similar to "Select All" in that it will select values that are currently excluded by other filters.
Pretty simple, this clears the field you've clicked on. This operates the same way as clicking the "x" on a field.
Clear Other Fields
This clears all fields other than the one you have selected. Try it out!