In the last decades, the integration of informatics applications supporting planning, scheduling and control has been a serious concern of the industrial community. Many standards have been developed to tackle this issue by addressing the exchange of data between the scheduling function and its immediate lower and upper levels in the planning pyramid. However, a more comprehensive approach is required to tackle integration problems, since this matter entails much more than data exchange. So, this article presents an ontological framework that provides the foundations to reach an effective interoperability among the various applications linked to scheduling activities.