Several recent papers have been devoted to the study of contracts as a way to formally specify abstractions of the behavior of software systems. A common aspect that gathers together some of these studies is a notion of compliance. This is a relation between systems which want to interact. Before starting the interaction, contracts are statically checked for compliance: when enjoyed, it guarantees that systems respecting their contracts will interact correctly. Since distributed applications are often constructed by dynamically discovering and composing services published by different (possibly distrusting) organizations, compliance becomes relevant to protect those services from each other's misbehavior.