3.2.5 Notation for classes
For reasons of clarity it will be useful to distinguish things in the real world, such as the list of categories produced above, from the conceptual classes and objects that will represent them in our model. To make this distinction clear, we will be showing, as above, categories of entity from the system domain in the same font as the rest of the text, and starting with a lower case letter unless at the beginning of a sentence (or, as in the case of ‘DVD’, where the entity name itself starts with an upper-case letter). However, the corresponding conceptual classes in the model (and their attributes) will be denoted in a different font dvd. It is important to realise that the classes being dealt with are conceptual classes and not software classes.
Class names are always singular nouns, and each name should be a single word starting with an upper-case letter. The name chosen for a class should give some indication of the type of entity its instances are supposed to represent. Where more than one word is needed to achieve this, we will run the words together, capitalising the first letter of each word bar code reader.
Applying these notational rules to the list of classes we have decided to include in our model for the DVD Library System, we have dvd, film memberand loan.
It is important to adhere to a set of agreed conventions for naming and capitalisation.