This document discusses model-driven trace diagnostics for pattern-based temporal specifications. It presents TemPsy-Check, a tool for model-driven trace checking of properties expressed in TemPsy, a pattern-based temporal specification language. TemPsy-Check yields boolean verdicts but provides no information on why a property fails. The document proposes a three-part approach to trace diagnostics: 1) characterizing property violations, 2) collecting diagnostics information using OCL queries on a trace meta-model, and 3) visualizing diagnostics information. It evaluates TemPsy-Report, a tool implementing this approach, and examines its scalability.