A system for generating a model representing an existing computer based business process involves analysing existing source content (910) which has annotations (920) added, to provide information for the modelling. Static analysis of the annotations can provide some of the information. Other information can be discovered at run time if the annotations alter the run time behaviour to generate monitoring events showing the behaviour. The annotations need not be restricted to codes or symbols or structures of the language of the source content, and can use concepts closer to those in the model being generated. Using annotations rather than manual modelling can reduce errors and lead to better predictions of performance from the model, and result in better reconfiguration of the software or the computing infrastructure to make more efficient usage of shared resources.