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N-dimensional space navigation is only possible in a logical rather han a physical world.

Progression from enumerated hierarchies to faceted schemes has been made in database management systems between 1960s and late 80’s. N-dimensional space navigation is only possible in a logical rather han a physical world.

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N-dimensional space navigation is only possible in a logical rather han a physical world.

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  1. Progression from enumerated hierarchies to faceted schemes has been made in database management systems between 1960s and late 80’s 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

  2. Jones Nut Bolt Screw Cog e.g. Suppliers and Parts - hierarchies 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

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

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

  5. 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 …….. Maintaining the connections in the network now becomes very complex - the work involved in updating the database is significant

  6. P# PNAME COLOUR WEIGHT P1 Nut Red 12 P2 Bolt Green 17 P3 Screw Blue 17 S# SNAME STATUS CITY S1 Anjer 30 Oslo S2 Pollitt 20 Huddersfield S3 Smith 10 York S# P# PRICE S1 P1 12 S2 P1 10 S3 P1 50 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:

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

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