Discovery
The assessment interview needs to be held in a highly structured way, first defining Use cases which would reveal who are the actors (user roles), and what are their activities, which can range from the real world, and crossing into the IS. Both are important to get the big picture which is necessary to be able to design a comprehensive, holistic and extensible system.
Modeling (UML, Entities, Class diagrams)
UML diagrams of use cases can then be expanded into activity or sequence diagrams to get a better picture of what should be happening in the IS, which would at the end lead us to what information needs to be stored in what groups - identifying entities - and what should be the relations between those entities. This is best described by a Class diagram which is often used in database modeling.
Normalization
The model is then transformed to one of the Normal Forms, and is ready for implementation.