Heap has introduced a feature that allows users to define web events using hierarchical CSS selectors, making it easier to retroactively analyze user interactions without needing new code or waiting for data collection. This capability enables users to identify interactions, such as clicks on a gallery image, even if class names weren't initially assigned to elements, by using a hierarchical approach similar to CSS selectors. The data on these interactions is computed instantly and can be used for segmenting and constructing cohorts as if they had been tracked from the start. This feature has been available since November 17, 2013, allowing queries involving hierarchical events to access data from that date forward, while non-hierarchical events continue to function as before.