1. A computer implemented method to execute a runtime callback function, comprising: transforming multidimensional analytical metadata associated with an application server into an in-memory executable metadata, to generate an instance of an in-memory executable calculation scenario; analyzing the instance of the in-memory executable calculation scenario to determine one or more process callbacks associated with one or more nodes of the in-memory executable calculation scenario; based upon the determined process callbacks, a processor of the computer executing the runtime callback function by executing a selection callback at the nodes of the in-memory executable calculation scenario, and executing a transformation callback at one or more part providers associated with the in-memory executable calculation scenario.