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Exercise No. 22: Travel Booking (dfm)

In this E/R schema a customer - who is of a certain type - books a travel in a travel agency. The travel agency works for a certain tour operator. The travel goes to a certain destination which belongs to a certain country. The time dimension consists of month, quarter and year.

Figure D.E.46.1 - travel booking

Please identify the fact of interest and build the attribute tree. Some attributes cannot be used for aggregation in a meaningful way. Those should be tagged as non-dimension attributes in the fact schema.

Then derive the fact schema from the tree by defining dimensions, fact attributes and hierarchies and build a glossary for the fact attributes if there are any.

Solution

Entity BOOKS is chosen as the only fact. Its identifier becomes the root of the attribute tree. All other attributes or identifiers become nodes.

Figure D.E.46.2 - The attribute tree

Customer, travel and travel agency are defined as dimensions, dimension month is introduced as a range of the date attribute.Costs becomes the only fact attribute.

The address of a customer and and the description of a travel cannot be used for aggregation and are tagged as non-dimension attributes.

Figure D.E.46.3 - The fact schema

costs = SUM (BOOKS.costs)

This exercise is part of a case study: dfm - apa - log

Exercises List