Class Model

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A class model describes the data of a system: classes, their attributes, the references between classes and the data types the values come from. Multiplicities, value ranges and string patterns are set here as well.

Create two models

Create a model Data Types of the type ClassModel and a second model Sample. The first holds a vocabulary of data types, the second the classes. Other models can then use the same types.

Data types are model elements just like classes, so a model may consist of types alone.

The vocabulary of types

Add to Data Types:

• string type String, boolean type Boolean, UUID type UUID;
• numeric type Integer with fractionDigits 0;
• numeric type UnsignedInt with size 32 and minInclusive 0;
• temporal type Date with instantUnits Year, Month, Day.

Add to Sample the two types only it needs: numeric Money (totalDigits 19, fractionDigits 4, minInclusive 0) and enumerated Color with the literals Red, Green, Blue, Black.

Classes

Add four classes to Sample. A class owns properties, and a property is either an Attribute with a data type or a Reference to another class. Both have a multiplicity.

Class	Properties
User	firstName, lastName, birthDate [0..1], email [1]
Order	deliveryAddress String [1]
OrderItem	quantity UnsignedInt [1], price Money [1]
Product	abstract, name String [1]

Add Book with the attribute author and Pen with the attribute color. Draw Generalization from each to Product.

References

Owner	Reference	Target	Kind	Multiplicity
Order	user	User	Association	[1]
Order	items	OrderItem	Composition	[0..*]
OrderItem	order	Order	Association	[1]
OrderItem	product	Product	Association	[1]

Set items and order as opposite to each other - on the diagram the two references become the two ends of one edge.

Textual representation

Open the model as text. This is the same model written as source: renaming a class in the text renames it on the diagram.

classModel Sample

class Order {
    attribute deliveryAddress String
    reference user User
    composition items OrderItem [0..*] opposite order
}

abstract class Product {
    attribute name String
}

class Book extends Product {
    attribute author String
}

enumerated Color {
    Red
    Green
    Blue
    Black
}