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1. Types and Instances

Read the following case study and decide whether the statements below are true or false.

Trains on a rapid transit system are classified into passenger trains and maintenance trains.  Passenger trains are numbered in the range 1001 to 6999 and maintenance trains are numbered in the range 8001 to 9999.  

(i) 'Passenger trains' and 'Maintenance trains' are instances of the type 'Train type'.   TRUE  or  FALSE?

(ii) 'Train number 2718' is an instance of the type 'Passenger train'.   TRUE  or  FALSE?

(iii) Trains with numbers in the range 8001 to 9999 are types of 'Maintenance trains' TRUE  or  FALSE?

2. Private Attributes

Explain why class attributes are normally PRIVATE.

3. Cardinality

Consider the following class diagram.

Which of the following statements are true and which are false?

(i) Customers must buy at least one product line  TRUE  or  FALSE?

(ii) A product line is bought by zero or more customers TRUE  or  FALSE?

(iii) You cannot be a customer unless you have bought at least one product TRUE  or  FALSE?

4. Attributes

Explain the circumstances under which you would want to make an attribute of a class, a separate class by itself.

5. Use Cases

Explain the use of the stereotype <<extend>>.

6. Sequence Diagrams

Which statement is true about a sequence diagram:

1. shows the lifetime of a set of objects and how they pass messages between one another for a given use case scenario

2. shows the possible interactions which may exist between a set of classes

3. shows the lifetime of a set of objects through the events which may occur in a time-ordered sequence

4. shows the interfaces between users (actors) and the system

5. none of the above.

7. Decision Tables

The following processing is described by the decision table below.

When a telephone user dials a number, the system checks to see whether the exchange limit (the number of telephone lines in the exchange) is exceeded and whether the user's credit has been exceeded.  If the exchange line limit or user's credit is exceeded the call is refused.  Otherwise, if the call is an international call, it is routed to an international call handler and if the call is a domestic call, it is routed to a domestic call handler.

Using the procedure to check the number of rules, see whether the above decision table is complete and, if not, identify which rule is missing.