It is widely accepted practice to build domain models as a conceptual basis for software systems. Normally, the conceptual schema cannot be supplied by domain experts but is constructed by modelling experts. However, this is infeasible in many cases, e.g., if the system is to be generated ad hoc from a conceptual schema. This paper presents an iterative process that helps domain experts to create a conceptual schema without the need for a modelling expert. The process starts from a set of sample instances provided by the domain expert in a very simple form. The domain expert is assisted in consolidating the samples such that a coherent schema can be inferred from them. Feedback is given by generating a prototype system which is based on the schema and populated with the provided samples. The process combines the following three aspects in a novel way: (1) it is based on a large amount of samples supplied by the domain expert, (2) it gives feedback by agile generation of a prototype sys...