The document discusses stream processing and querying of process logs. It defines a process log as a mapping of case identifiers to traces, which are sequences of events. Queries can check properties of individual traces or perform aggregations across multiple traces. Hyper-queries generalize this to operate on the full log. Various methods of incrementally evaluating queries and hyper-queries are discussed as the log is produced, such as processing one case or event at a time. The state of the art in constraint and query languages is reviewed.