If you have problems refer back to the previous section. Back to top Many to many relationships Now for the more complex situation. The one to many situation described above is rather restrictive as some patients may have more than one doctor. In other words the above model does not cater for all situations that could occur. This does not effect the Rumbaugh diagram as it is not really necessary to shown the table required in the database to solve the problem, however some people do prefer you to do this and it may help you create the database.
People get very excited by attributing a great deal of knowledge and meaning to databases.
In the '80s a great deal of research went on in developing 'semantic models'. These were basically modelling techniques which had a wider range of modelling symbols, such as inheritance which we have come across in object oriented modelling. Therefore the meaning, or rather the semantics of the model are these elements nothing more or nothing less. Date 1995 p346 - 371, provides, for this area of work, an unusually lucid account of semantic modelling i.e. what we have been doing in this chapter with the models. They usually require programmers to implement, although a lot can be done with filtering out certain records and querying the records in some way.