Various principles govern the successful selection of engineering 'entities', by which we mean materials, manufacturing processes, components or assembled products. The principles are described here, with examples. There are two fundamental steps in any selection exercise: 'Screening', to identify viable candidates, and use of 'Supporting Information' to enable a final choice. Data sources must ... [Show full abstract] be appropriately structured to support these steps. The paper discusses these and other basic issues of database design, including data taxonomy, rules for the choice of attributes (fields), the relationships between entities (records), and data checking and estimating procedures. The examples are drawn mainly from the selection of materials, but the principles are general and apply to a wide range of selection problems.