A software system for any information system can be developed following a model driven paradigm, in particular MDA (Model Driven Architecture). In this way, models that represent the organizational work are used to produce models that represent the information system. Current software development methods are starting to provide guidelines for the construction of conceptual models, taking as input requirements models. In MDA the CIM (Computation Independent Model) can be used to define the business process model. Though a complete automatic construction of the CIM is not possible, we have proposed in other papers the integration of some natural language requirements models and we have defined a strategy to derive a CIM from these models. In this paper, we present an improved version of our ATL transformation that implements a strategy to obtain a UML class diagram representing a preliminary CIM from requirements models allowing traceability between the source and the target models.