Each screen field corresponds to a database column. However, the predefined screens represent only a small subset of the column combinations that users need for querying the catalog. As StarView services a wide and diverse group of users, the interface must provide the flexibility to query the catalog by the combination of columns that best suits a user's needs. Moreover, users should not be required to understand the topology of the database when formulating queries requiring joins. In the UR approach, users need only specify columns of interest, and the interface software infers the underlying joins for the corresponding query.
Most astronomical databases are single-table catalogs describing sky objects and their properties.
Each catalog row corresponds to an object and each column refers to a property of the object. Many user interfaces are designed to display the data of a single astronomical table. The query mechanism for such interfaces is straightforward because there are no table joins to calculate. Some applications require that more than one table be queried at a time. For instance, a user interface that cross-correlates more than one table must be able to query multiple tables.