What are data models, and why are they needed?
Wikipedia offers the following definition of a Data Model:
A data model is an abstract model that organizes elements of data and standardizes how they relate to one another and to properties of the real world. For instance, a data model may specify that a data element representing a car comprises of a number of other elements which in turn represent the color, size, and owner of the car.
In addition, the Wikipedia entry goes on to say the following:
A data model explicitly determines the structure of data.
Taking the analogy of computer programming languages, data models can be compared with data structures.