Answer to Question 1
Person is a superclass with a Work responsibility. Person can have numerous subclasses, including Doctor, Mechanic, and Cook. Instances of all subclasses must work, but the work that they actually do is very different from each other: when objects belonging to Person subclasses are told to work, the Doctor treats patients, while the Mechanic fixes cars and the Cook prepares food. In other words, the same message, Work, is implemented differently depending on the nature of the object, not the nature of the message.
Answer to Question 2
A use case diagram is a visual meta-model: it does not model the use case itself, but the associations between actors, use cases, and the system. It also depicts extend and include relationships between use cases and provides us with a visual table of contents. An activity diagram is a general-purpose diagram for visualizing and verifying a logical flow. For a use case with a complicated alternate flow, an activity diagram is a very helpful tool. Its simplicity facilitates communication between development stakeholders.
Incentive spirometry. A portable incentive spirometer is useful for encouraging patients to exercise
Letter from a Person with Pure Alexia
James A. Garfield lies mortally wounded. After failing to locate the bullet, surgeons called in Alex
The Middle East and Operation Desert Storm
Work and Gender: Women at Work in India
Biology multiple choice questions