The Vision of Britain system holds a large library of historical statistics. We store all the data values in one big list, and for each value we record:

• WHERE the data value is for, by links to our administrative gazetteer
• WHEN the value is for, by a year or period
• The SOURCE, linking to our listings of Census Reports

We record WHAT each number measures via our implementation of the Aggregate/Tabular Data Extension developed by the Data Documentation Initiative. This places each data value within an nCube whose dimensions are defined by variables (sometimes organised into variable groups), like occupation and gender and age, each of which is a set of categories, such as "Males" and "Females":

The implementation is structured as an ontology containing 5,634 entities of the following types, linked by 18,465 relationships: