fmcalisto / phonebook

The PhoneBook Example

The PhoneBook Example

Let us imagine that we want to build a simple PhoneBook application, capable of storing a set of contacts for each registered person. A person has a name and each contact is represented by a name and a phone number.

Describing the Domain

The domain model of the PhoneBook application consists only of three entities: PhoneBook, Person and Contact. The PhoneBook entity represents the class that knows all registered people. Each person maintains his/her own set of contacts.

Describing entities using the DML

Using the DML, we could textually describe the domain model of our PhoneBook application through the following DML code:

1. class PhoneBook;
2.
3. class Person	{
4. 		String	name;
5. }
6.
7. class Contact {
8. String name;
9. String phoneNumber;
10. }

There are other business rules that should be implemented. For instance, consider that it should be possible to remove a Contact given its name, and getting all Contact instances whose name contains a given substring. These would correspond to the implementation of methods in the Person class with the desired functionality.