Deletion model Types of deletion event affecting less than three pre-existing runs. White area indicates run of undeleted terms. Lightly shaded area indicates run of previously deleted terms. Darker area represents current deletion event. A: creates one new run with r = 1. B: lengthens left hand run to r + 1 events. C: lengthens right hand run to r + 1 events. D and E: merge two runs to create a single run with r + s + 1 deletion events.