A computer-implemented technique is described herein for receiving activity signals from plural logic components running on one or more computing devices. Each activity signal includes an activity information item (AII) that describes an activity performed by a subject (e.g., a user), or to be performed by the subject, as recorded by a logic component. The technique stores AIIs extracted from the activity signals in a graph data structure. The technique then: determines, by interrogating the graph data structure, one or more activity clusters within a span of time, each activity cluster pertaining to a group of AIIs associated with a same encompassing project; generates one or more summary documents based on the identified activity cluster(s); and sends the summary documents to an output device.