A comparison between Willner's criteria and the present proposal. Willner's criteria are represented by the brown circles and our nine criteria are represented by squares with the same color code as in Figures 1 and 2. Where a square fully overlaps with one of Willner's criteria (or with one aspect of one of Willner's criteria) it is represented inside the corresponding circle. Where it partially overlaps, it sits astride the circle. Where the criterion (or an aspect of it) has not been described by Willner, it stands outside the circles. Arrows indicate which sub-aspect of Willner's criteria corresponds to our proposed criteria.