This is a proper attribute of Melon, but an inherited attribute of Honeydew. The following diagram shows the hierarchy already established, expanded to show the attributes of the classes. The problem here is that there might be many green watermelons, that came from a 15 foot vine and weighed 1.25 pounds. To fully specify an instance there must be some way to uniquely identify each watermelon to distinguish between those with identical characteristics. There can be one or more values for list attributes.
Tables are complex attributes with related sub-components.
21205 reference Reference attributes are those which point to another object in the database. If we expand the example model to have a new class, Orchard , then Apple can have the reference attribute from orchard with which we can reference an instance of orchard. Some attributes values may be determined based on other attributes in that object or another related object. These attributes are called derived attributes and are only of concern to those wanting to insert or edit objects. Their values are not directly editable except by changing the values from which they are derived.