if you are interested in where todays databases are based on you might interested in the following link:
for example these requirements ( taken from the link above ) have been defined back in the 1970ies and are still valied today:
- To provide a high-level, nonnavigational user interface for maximum user productivity and data independence
- To support different types of database use including programmed transactions, ad hoc queries, and report genereration
- To support a rapidly changing database environment, in which tables, indexes, views, transactions, and other objects could easily be added to and removed from the database without stopping the system.
- To support a population of many concurrent users, with mechanisms to protext the integrity of the database in a concurrent-update environment
- To provide a means of recovering the contents of the database to a consistent state after a failure of hardware or software
- To provide a flexible mechanism whereby diffent views of stored data can be defined and various users can be authorized to query and update these views
- To support all of the above functions with a level of performance comparable to exsiting lower-function database systems.