Introduction to Relation
The relation we are going to study here is
an abstraction of
relations we see in our everyday life such as those between parent and child,
between car and owner,
among name, social security number, address and telephone number etc. We are going
to focus our attention on one key property which all the everyday relations
in common, define everything that has that property as a relation, and study
properties of those relations.
One of the places where relation in that sense is used is data base management systems. Along with hierarchical and network models of data, the relational model is widely used to represent data in a database. In this model the data in a database are represented as a collection of relations. Informally, each relation is like a table or a simple file. For example, consider the following table.
|Amy Angels||35 Mediterranean Av.||224-1357|
|Barbara Braves||221 Atlantic Av.||301-1734|
|Charles Cubs||312 Baltic Av.||223-9876|