The main goal of this work is to develop an initial characterization of an information systems design approach that we call implicit invocation and to analyse its potential advantatges and disadvantatges with respect to the conventional approach that we call explicit invocation. Our work tries to contribute to this approach at the specific field of object oriented design of information systems. In our analysis we use an example that consist in some simplified banking operations, that we use as basis for the comparation of the alternative designs we explore. We characterize what could be implicit invocation in information systems design, we apply this characterization to the example, and we present a comparative analysis of the two designs.