In this session we will discuss what is dimensional data model, why do we use it for data warehousing, when to use and when not to use, what are the advantages and disadvantages and what are the alternatives. We will put dimensional modelling into practice by designing a data mart using a case study. That way we can get first hand experience about how a 3rd normal form transactional database is translated into fact and dimension tables in a dimensional model. Time permitting, we will also discuss some particular points in dimensional modelling such as smart date key, choosing dimensional grain, and real time fact table.