Designing information systems with adaptation capacities is a challenge of great importance to improve the appropriation of the system by the users. In this paper we view visualized digital traces as a means to support reflexive type coupling between the system and the user. We examine the way users make use of digital traces with the objective of identifying possible use invariants. This is an indispensable stage in the enrichment of a trace system. We present a case study of an instrumented collaborative situation that answers this question. This case study uses theoretical and methodological tools from cognitive ergonomics that enabled us to integrate the subjects' point of view in the activity analysis. This study allows us to formalize four schemas of trace usage. We discuss these results with regard to the appropriation and adaptation of information systems. This leads us to argue that a trace-based approach is promising for the design of adaptive information systems.