Back to the Data Model.
The Draft Business Rules have been defined and are listed below.
The Data Model shows :-
1) A Super-Type called 'Things of Interest'.
2) Two Sub-Types of Hotels and Restaurants.
Each of these Sub-Types inherits all the attributes of the parent Super-Type of 'Things of Interest'.
In addition, they have attributes of their own.
The design of the corresponding Physical Database for Inheritance offers three choices :-
1. Create separate Tables for the Sub-Type and each Super-Type.
2. Combine all attributes of the Sub-Types upwards into the Super-Type.
This results, of course, in one physical Table.
This is shown in the Denormalized Design.
3. Combine all attributes of the Super-Type downwards into Tables for each the Super-Type.
This results in two physical Tables in this example of a City Guide.
This is left as an exercise for the student.
A. The Area being Modelled is :- A Web Site providing a City Guide for Tourists. B. The Things of Interest, ('THINGS'), include :- B.1 Addresses B.2 Cinemas B.3 Events of Interest B.4 Individuals B.5 Movies B.6 Museums B.7 Restaurants B.8 Star Ratings for Hotels. B.9 Things of Interest B.10 Types of Food for Restaurants B.11 Visitors Comments. C. These THINGS are Related as follows :- C.1 An ADDRESS can be associated with zero, one OR or many EVENTS_OF_INTEREST. C.2 An ADDRESS can be associated with zero, one or many INDIVIDUALS. C.3 An ADDRESS can be associated with zero, one OR or many THINGS_OF_INTEREST. C.4 An HOTEL_STAR_RATING can be associated with zero, one OR or many HOTELS. C.5 An INDIVIDUAL can be associated with zero or one ADDRESS. C.6 An INDIVIDUAL can be associated with zero, one OR or many THINGS_OF_INTEREST. C.7 An TYPE_OF_FOOD can be associated with zero, one OR or many RESTAURANTS. D. Other Characteristics of these THINGS include :- D.1 A THING_OF_INTEREST can have zero or one Contact INDIVIDUAL. E. Sample Data includes :- To be determined F. Typical Enquiries include :- F.1 Where can we find a Chinese Restaurant ?
15th. December 2002