Class Diagrams

Question 1

class

Answer 1

a construction plan for a set of similar objects

Question 2

operation <-> method

Answer 2

operation - specification
method - implementation

Question 3

class structure

Answer 3

name
attributes
operations

Question 4

attribute visibility

Answer 4

• • public: every other class
• • private: only the class itself
• # protected: class itself and subclasses
• ~ package: classes in the same package

Question 5

primitive data type

Answer 5

pre-defined
user-defined

Question 6

pre-defined types

Answer 6

Boolean, Integer, String, UnlimitedNatural

Question 7

user-defined

Answer 7

These are custom data types that the user can define using the stereotype «primitive». They represent atomic values and can’t be broken down into more specific types within UML models

Question 8

composite

Answer 8

Represented with the stereotype «datatype», these types are similar to classes but specifically used for defining value types
- Instances are values not objects
- Identity defined by its properties
- Immutable

Question 9

enumerations

Answer 9

Enumerations are special data types defined with the stereotype «enumeration» in UML.
They specify a list of possible named values, known as enumeration literals, that an instance of this type can assume.

Question 10

Pre-defined properties

Answer 10

• {readOnly} … value cannot be changed
• {unique} … no duplicates permitted
• {non-unique} … duplicates permitted
• {ordered} … fixed order of the values
• {unordered} … no fixed order of the values

Question 11

Direction of the parameter

Answer 11

• in … input parameter
  
  • When the operation is used, a value is expected from this parameter
• out … output parameter
  
  • After the execution of the operation, the parameter has adopted a new value
• inout : combined input/output parameter

Question 12

Default

Answer 12

instance variable (= instance attribute): attributes defined on the instance level

Question 13

Class variable (= class attribute, static attribute)

Answer 13

• Defined only once per class,
  
  • i.e., shared by all instances of the class
  • e.g., counters for the number of instances of a class, constants, etc.
• Class operation (= static operation)
  
  • Can be used if no instance of the corresponding class was created
    
    • e.g., constructors, counting operations, math functions, etc.
• Notation: underlining the name of class variable or class operation

Question 14

coarse grained -> fine grained

Answer 14

Name -> Name + Attributes + Operations -> Name + Attributes with V,Dt + Operations with V, Dt

Question 15

navigability

Answer 15

an object knows its partner objects and can
therefore access their visible attributes and operations

Question 16

non-navigability

Answer 16

Indicated by a cross, but this is also often left out

Question 17

Aggregation

Answer 17

Used to express that a class is part of another class

• Properties of the aggregation association:
  
  • Transitive: if B is part of A and C is part of B, C is also part of A
  • Asymmetric: it is not possible for A to be part of B and B to be part of A simultaneously
• Two types:
  
  • (Shared) aggregation
  • Composition

Question 18

generalisation

Answer 18

transitive

Question 19

Generalization – abstract classes

Answer 19

• Used to highlight common characteristics of their subclasses while ensuring no direct instances of the superclass
• Only its non-abstract subclasses can be instantiated