Database

A database is structured collection of data. Thus, card indices, printed catalogues of archaeological artefacts and telephone directories are all examples of databases. Databases may be stored on a computer and examined using a program. These programs are often called `databases', but more strictly are database management systems (DMS). Just as a card index or catalogue has to be constructed carefully in order to be useful, so must a database on a computer. Similarly, just as there are many ways that a printed catalogue can be organised, there are many ways, or models, by which a computerised database may be organised. One of the most common and powerful models is the `relational' model (discussed below), and programs which use this model are known as relational database management systems (RDMS).

Computer-based databases are usually organised into one or more tables. A table stores data in a format similar to a published table and consists of a series of rows and columns. To carry the analogy further, just as a published table will have a title at the top of each column, so each column in a database table will have a name, often called a field name. The term field is often used instead of column. Each row in a table will represent one example of the type of object about which data has been collected. Table 1(a) (p. ) is a an example of a table from a database of English towns. Each row, in this case a town, is an entity, and each column represents anattribute of that entity. Thus, in this table `population' is an attribute of `town.'