video record
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This programme shows how the database management system of Overseas Containers Ltd. retrieves information about the firm's voyages.
Metadata describing this Open University video programme
Module code and title: M352, Computer based information systems
Item code: M352; 05
First transmission date: 08-06-1980
Published: 1980
Rights Statement:
Restrictions on use:
Duration: 00:24:30
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Producer: John Jaworski
Contributors: Mike Newton; Geoff Stacey
Publisher: BBC Open University
Keyword(s): Container ships; Data base management systems; Liverpool Bay; Singapore
Footage description: The programme opens with film of the container ship 'Liverpool Bay' at sea. Mike Newton introduces the programme, explaining that it will examine how OCL can use their database to discover when the 'Liverpool Bay' will arrive at Singapore. With the help of a diagram of the OCL data-model examined in M352/04 he explains the significance of the VOYAGE record and the STOP record. Another diagram shows how all the Liverpool Bay's ports of call are recorded in the database. Newton uses an animated diagram of the Data Base Management System (DMBS) to show how it gets hold of specific records. With the aid of a studio model he explains the relationship between the user program, the schema, the subschema and the physical database description. He explains that the first problem is to understand how the data in the schema is supplied by the computer. Geoff Stacey, of Edinburgh Regional Computer Centre, shows how the printout of the schema produced by the database administrator relates to the diagram of the schema used in sequence 2. Using animated diagrams he explains how the schema-processor tabulates data in the schema, specifically the voyage record. With the help of a studio graphics board he explains how the diagramatic schema is translated into a form the DBMS can use. Mewton briefly introduces the next section, which is concerned with the selection of data from storage. Using a studio model of a magnetic disc pack, Stacey explains how the database is physically organised on a disc. Taking a specific example he then uses video animation to explain the importance of 'pointers' in locating information. Newton briefly introduces the next stage - connecting the schema tables with the actual data on the disc. Stacey shows us the written form of the physical database description provided by the database administrator. He uses this to explain how the physical description is held by the DBMS. Brief video animation depicting a record table being extended. Newton sums up what's been achieved so far. He then explains that the programme will follow through the sequence of operations that happens when the DBMS retrieves the 'Liverpool Bay's arrival date at Singapore. Stacey uses the studio graphics board to indicate two program statements that need to be executed. He follows through the operations of the DBMS in retrieving the appropriate record, using its tables. Video animation is used to clarify each step in the DBMS retrieving the relevant port-name, arrival date and departure date for this particular voyage of the 'Liverpool Bay'. Newton concludes by emphasising that the operations examined in this programme must be multiplied several thousand times to reflect the complexity of OCL's database management system.
Production number: 00525_4275
Videofinder number: 4177
Available to public: no