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OO class modelling 1 »

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Data/ Attribute Normalisation »

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First, it is important to remember to answer each part of the question.  Make it clear which part of the question you are answering by using the question parts indicated (a, b and c). It is useful to start each part of your answer on a new page, allowing you to add extra detail after your initial answer. 

• Answer to part a
• Answer to part b

• Answer to part c

Part a

The significance of the third point is that even though a flight number provides standard details about a flight, e.g. origin and destination,  the departure time of the flight varies according to the date.  Therefore the functional dependency diagram that departure time is dependent upon both flight number and date, whilst from-code and to-code is only dependent upon the flight number.

Part b

The first problem is that there is a repeating group of fields (which relate to each journey leg), therefore these need to be removed to make the classes into 1NF.

TICKET (ticket-number, passenger-name, issue-date, booking-reference)

TICKET-LEG (ticket-number, journey-leg, from-code, from-airport, to-code, to-airport, date, flight-number, departure-time)

For 2NF, all non-identifying fields must be dependent upon the whole of a key. 

All classes are already in 2NF, since in TICKET all non-identifying fields are dependent upon ticket-number and in TICKET-LEG, all non-identifying fields are dependent upon ticket-number and journey-leg (together).

For 3NF, no non-identifying field must be dependent upon another non-identifying field.  In this case, there are relationships between airport code and airport name which violate 3NF and therefore these are removed to create separate classes.

TICKET (ticket-number, passenger-name, issue-date, booking-reference)

TICKET-LEG (ticket-number, journey-leg, from-code, to-code, date, flight-number, departure-time)

FROM (from-code, from-airport)

TO (to-code, to-airport)

Part c

The data flow diagram showing the appropriate control processes and flows are shown on the attached diagram.

The corresponding state-transition diagram for the checkin-control process is shown on the attached diagram.

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