Thanks Dusan. I've been trying to get my head around data warehousing, and in my googling I notice that there is an issue with teaching the whole multidimensional data cube type stuff. It's just hard. I've been wondering if this might be a genuine use case for virtual environments - teaching with interactive visualisations of projections of the datasets onto different axes, ability for people to move through the data volume and so on. If only I had time to try it :-)