Data structure design is the most fundamental part of design. It essentially dictates what data needs to be stored and how that data will be organised. This will then have a direct impact on how the rest of the design goes. It is almost impossible to produce an input or output design without knowing exactly what the inputs or outputs actually are.

The data structure design tends to start with listing out all the data that is required. This information would of already been gathered in analysis and most likely during document collection. This information will then be placed into a big list known as a data dictionary.

After the data dictionary has been created it is important to put some structure to the data. This normally means linking related items of data together to form tables. An example is shown below

This can then be separated out into two tables.

The above is an example of normalization. Also the above diagram is an example of an entity relationship diagram (ERD).

It should be fairly clear that like for like data elements are stored in the same tables. The bold text is the name of the table. At this stage just think of this as a way of identifying how the data stored in that table is related.