1. A computer program product comprising computer program code stored on a tangible computer readable storage medium which, when executed on a data processing system, instructs the data processing system to generate a model comprising: a representation of a first node corresponding to a first function executing in the software system which obtains access to a resource, with an indicator of a number of times the first function has been called in the software system; a representation of a second node corresponding to a second function executing in the software system while the resource is accessed, with an indicator of a number of times the second function has been called; a representation of a place holder node with an indicator that the place holder node has never been called in the software system, the representation of the place holder node has never been called further indicating that the place holder node does not represent a function; a representation of a first call from the first node to the place holder node; a representation of a second call from the place holder node to the second node; and wherein the first and second calls correspond to the first function calling the second function in the software system and the model of the software system under execution provides information regarding which functions are called while the resource is being accessed.