1. N-dimensional space navigation is only possible in a logical rather han a physical world. They didn’t have any books to look after - their information store was electronic Progression from enumerated hierarchies to faceted schemes has been made in database management systems between 1960s and late 80’s

2. Early (1960’s - late 1980s) computer database products used hierarchic and network models that modelled data and the way in which it was physically stored e.g. Suppliers and Parts - hierarchies Jones CogBoltScrewNut

3. To access different suppliers for the same part required either a) a lot of searching b) a second hierarchy Nut AnjerSmithClarkJones Data was now duplicated - updates to the database were more complicated.

4. Each new requirement could bring about additional duplication and increases the problems of data integrity Duplication could be removed by using a network model. Nut AnjerSmithClarkJones Nut

5. Maintaining the connections in the network now becomes very complex - the work involved in updating the database is significant e.g. Adding a new suplier for a given part MOVE ‘S4’ TO S# IN S FIND CALC S ACEPT S-SP-ADDR FROM S-SP CURRENCY FIND LAST SP WITHIN S-SP while SP found PERFORM ACCEPT S-SP-ADDR FROM S-SP CURRENCY FIND OWNER WITHIN S-SP GET P IF P# IN P < ‘P3’ leave loop END-IF FIND PRIOR SP WITHIN S-SP END-PERFORM etc ……..

6. The relational model proposed by E F Codd in 1970 introduced a simpler scheme that would minimise duplication and facilitate different ways in which to view the data: P# PNAME COLOUR WEIGHT P1 NutRed12 P2 Bolt Green17 P3 Screw Blue17 S# SNAME STATUS CITY S1 Anjer30Oslo S2 Pollitt20 Huddersfield S3 Smith 10 York S# P# PRICE S1 P1 12 S2 P1 10 S3 P1 50

7. The navigation of the network was replaced by operations using SQL - Structured Query Language e.g. INSERT INTO SP (S#, P#, PRICE) VALUES (S4’,’P3’,14)