19. The system of claim 18 , wherein: summarizing the selected cluster comprises comparing at least part of the new observation to observations identified by the selected cluster, wherein at least some of the observations identified by the selected cluster are inconsistent with the summary attribute-value pairs of the selected cluster.
18. A system, comprising: one or more processors; memory storing instructions that when executed by at least some of the one or more processors effectuates operations comprising: obtaining a collection of clusters of immutable observations about entities, at least a plurality of the clusters each: corresponding to a respective entity, identifying immutable observations determined to describe the respective entity, and having summary attribute-value pairs that summarize the identified observations and collectively describe an inferred current state of the respective entity; receiving a new observation about a given entity; selecting a cluster among the collection of clusters based on correspondence of the selected cluster to the given entity; summarizing the selected cluster by updating at least some of the summary attribute-value pairs of the selected cluster based on both the new observation and the observations identified by the selected cluster; storing the updated attribute-value pairs in association with the selected cluster; and updating a user interface at a user device using the new observation.