Publish/subscribe is a widespread communication paradigm for asynchronous messaging that naturally fits the decoupled nature of distributed systems, allowing simple and effective development of distributed applications. In this paper we propose a framework which includes a model of a publish/subscribe computation and a few properties on the computation, namely completeness and minimality, that capture, from an application viewpoint, the expected behavior of a publish/subscribe system with respect to the semantic of the notification of the information. Finally, we provide also a centralized implementation of publish/subscribe system which produces minimal and complete computations.