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.
Relative Energy Consumption per Person for Selected Countries
A person with a defective "P" gene might only have it effect the Hair
concept map template
Circular friction over attachments at knee. Apply with fingertips or palms.
Use of a hand tool to apply pressure to a trigger point.
How do resultant force work among different angles?