Given the inherent autonomy, heterogeneity, and continuous evolution of Web services, mismatches usually exist between service protocols, and service interactions are typically conducted by means of adapters. A set of service protocols often can conduct multiple interactions, but a few, whose results fulfill the requestor's requirements, are expected. In this paper, we propose a technique to verify whether a certain expected interaction is adaptable. Then, a requestor can choose a suitable provide service from a set of functionally equivalent candidates according to her requirements. This technique complements the effort of adapter synthesization for achieving an expected service interaction.