30. The product of claim 29 , the operations comprising calculating the topical coherence value of the segment, wherein calculating the topical coherence value of the segment comprises calculating an average coherence of the segment, including averaging semantic similarities of pairs of the content items associated with the user actions clustered into the segment.
31. The product of claim 30 , wherein calculating the topical coherence value of the segment comprises: for each first content item, determining a semantic similarity between the first content item and each second content item, the first content item and second content item associated with the user actions clustered into the segment; for each first content item, determining a maximum semantic similarity between the first content item and the second content items; calculating an average value of the maximum semantic similarities of the first content items; and designating the average value as a maximum coherence of the segment.