Abstract: Apparatus arranged to allow a user to input a plurality of values of data elements of a table being a baseline version of the table having a version number b, the apparatus being arranged to store the values of the data elements in a database in the form of one or more baseline version records, each record containing at least one of the values of the data elements, the apparatus being arranged to allow a user to input a revised value of one or more of the data elements of the table thereby to define a change dataset representing the value of one or more data elements of a (b+n)th version of the table that are different from the value of one or more corresponding data elements of the b'th version of the table, the apparatus being arranged to store the difference dataset by generating one or more further records of the database, each further record corresponding to a baseline version record of the database, each further record containing at least one value of a data element of the difference dataset, the appara