UML Class Diagrams and Associations Quiz
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Questions and Answers

What characterizes an association class?

  • A class with no connection to other classes.
  • An association that includes attributes and operations. (correct)
  • An association that can only exist in one direction.
  • An association that serves only as a link between two classes.

    • Why are association classes often utilized in many-to-many relationships?

  • They provide a structure to minimize redundancy.
  • They restrict the number of instances created in relationships.
  • They eliminate the need for auxiliary methods.
  • They allow for the modeling of shared properties between two classes. (correct)

    • What is a defining feature of a qualified association?

  • It requires a qualifier to limit many relationships. (correct)
  • It can only establish one relationship at a time.
  • It does not use attributes to define relationships.
  • It does not support shared attributes.

    • How does the OwnsStock association class differ from ordinary classes in terms of occurrences?

    <p>It has only one occurrence for each unique pair of person and company. (A)</p> Signup and view all the answers

    In the context of user authorization, what aspect does the home directory represent?

    <p>An assigned location for each authorized workstation. (A)</p> Signup and view all the answers

    What is the primary purpose of an association in class diagrams?

    <p>To indicate a meaningful relationship between classes. (A)</p> Signup and view all the answers

    How should associations be properly named in UML diagrams?

    <p>Using a verb phrase. (B)</p> Signup and view all the answers

    What can an optional 'reading direction arrow' in an association indicate?

    <p>The preferred reading direction of the association name. (D)</p> Signup and view all the answers

    What does it imply if there are multiple associations between classes?

    <p>There exist diverse relationships between the classes. (A)</p> Signup and view all the answers

    What is the first step in the order of modeling?

    <p>Define classes (D)</p> Signup and view all the answers

    In the context of a flight model, what does a 'flight' class primarily contain?

    <p>A list of passengers and seats (D)</p> Signup and view all the answers

    Which of the following is NOT a function of UML class diagrams?

    <p>Modelling user interfaces. (C)</p> Signup and view all the answers

    Which class is directly associated with managing multiple accounts according to the qualified association?

    <p>Bank (A)</p> Signup and view all the answers

    What role does proper naming of associations play in UML diagrams?

    <p>It enhances understanding of the relationships. (D)</p> Signup and view all the answers

    Which of the following concepts is associated with associations in UML diagrams?

    <p>Multiplicity. (C)</p> Signup and view all the answers

    What is the multiplicity for accounts in relation to a bank?

    <p>0..* (C)</p> Signup and view all the answers

    What is the role of pilot and co-pilot in the flight model?

    <p>Operational role running the flight (B)</p> Signup and view all the answers

    What type of relationship is NOT typically depicted by an association line?

    <p>Inheritance. (D)</p> Signup and view all the answers

    In the flight model, each city must have at least what?

    <p>An airport (B)</p> Signup and view all the answers

    What does the attribute 'account number' signify in the account class?

    <p>It uniquely identifies an account (A)</p> Signup and view all the answers

    What type of relationship exists between a flight and its passengers?

    <p>One-to-many (B)</p> Signup and view all the answers

    What characteristic allows a subclass to inherit attributes and methods from a superclass in object-oriented programming?

    <p>Inheritance (C)</p> Signup and view all the answers

    Which of the following statements about an abstract class is true?

    <p>An abstract class can inherit from other classes. (C)</p> Signup and view all the answers

    In an object diagram, what does a rectanglar box represent?

    <p>An instance of a class (C)</p> Signup and view all the answers

    What does a line drawn between objects in an object diagram typically represent?

    <p>Association (A)</p> Signup and view all the answers

    Which method would belong to a Rectangle class based on the provided UML diagram?

    <p>getArea(): float (B)</p> Signup and view all the answers

    What is a defining feature of an object model in relation to a class model?

    <p>It shows objects' states at a single point in time. (B)</p> Signup and view all the answers

    Which of the following is true regarding the elements of an object diagram?

    <p>Object names and class names are presented in underlined format. (A)</p> Signup and view all the answers

    Which formula correctly represents the area of a Rectangle based on its attributes?

    <p>length x width (C)</p> Signup and view all the answers

    What type of objects do tangible items refer to in a class modeling context?

    <p>Physical entities in the domain (B)</p> Signup and view all the answers

    Which characteristic is essential for good modularization?

    <p>Maximal relationships within modules (A)</p> Signup and view all the answers

    What principle emphasizes maintaining simplicity in class modeling?

    <p>Simplicity makes models easier to understand (D)</p> Signup and view all the answers

    Which term describes the decomposition of system components into smaller, independent parts?

    <p>Modularization (A)</p> Signup and view all the answers

    Which of the following is a source of relevant objects for class modeling?

    <p>Tangible objects (D)</p> Signup and view all the answers

    What is an important consideration when naming classes?

    <p>Using descriptive and singular names (C)</p> Signup and view all the answers

    What does projection in the context of decomposition refer to?

    <p>Dependent modules with common elements (B)</p> Signup and view all the answers

    What does coupling refer to in the context of modular systems?

    <p>Relationships between different modules (D)</p> Signup and view all the answers

    What is meant by high cohesion in a component?

    <p>All elements work towards a single task. (A)</p> Signup and view all the answers

    Which type of cohesion is characterized by parts of a module performing unrelated functions?

    <p>Coincidental cohesion (A)</p> Signup and view all the answers

    Which of the following best defines functional cohesion?

    <p>Each element in the module is essential to one computation. (B)</p> Signup and view all the answers

    What is the internal structure of a component with high cohesion like?

    <p>All parts contribute to one cohesive task. (B)</p> Signup and view all the answers

    Which of these describes the implications of low cohesion effectively?

    <p>Increased complexity due to unrelated component functionality. (C)</p> Signup and view all the answers

    What is a major characteristic of a module with procedural cohesion?

    <p>It performs functions in a defined and specific order. (B)</p> Signup and view all the answers

    Which type of cohesion is regarded as the worst form of cohesion?

    <p>Coincidental cohesion (C)</p> Signup and view all the answers

    How does high cohesion within a component impact its maintainability?

    <p>Enhances clarity and makes it easier to maintain. (A)</p> Signup and view all the answers

    Flashcards

    Association

    A relationship between classes that shows a meaningful connection.

    Association Name

    A verb phrase that explains the relationship between classes.

    Reading Direction Arrow

    An arrow on an association line showing the direction to read the name.

    Multiple Associations

    Multiple relationships between the same classes.

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    Association Line

    A line that connects two classes, representing a relationship.

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    Multiplicity

    The number of objects that can participate in an association.

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    Role

    A specific role a class plays in an association.

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    Self-Association

    An association where a class relates to itself.

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    Modularization

    Decomposing a system into smaller self-contained units with clear boundaries.

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    Cohesion

    The degree to which elements within a module are related and work together cohesively.

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    Coupling

    The degree to which modules depend on each other.

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    Projection

    Decomposing a system into dependent modules where parts share common elements.

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    Partitions

    Decomposing a system into independent modules that can work separately.

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    Association Class

    An association class is a special type of association in a class diagram that acts as both an association and a class. It has its own attributes, operations (methods), and relationships. This means it can connect two classes and also hold its own data and behaviors.

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    Many-to-Many Association

    A many-to-many association is a type of relationship in which each element on either side of the association can be related to multiple elements on the other side.

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    Qualified Association

    A qualified association is a special type of association that uses a qualifier attribute to distinguish between multiple relationships of the same kind. This qualifier helps to make the relationship one-to-one between objects.

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    Association Class vs. Ordinary Class

    An association class helps to represent information that is specific to two connected classes instead of being solely associated with one class. This ensures that the information is shared properly.

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    Relationship Reduction

    A qualified association can be used to model one-to-one relationships even in a situation where multiple objects could be involved. This is achieved by adding a qualifying attribute that acts as a unique identifier. The qualifier helps narrow down the relationship to just one specific object.

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    Class Model

    A class model that represents relationships between classes in a system, including attributes, operations, and associations. It can be used to understand the structure and behavior of a system before implementation.

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    Model Order

    The process of defining classes, associations, and multiplicity in a class model. It's like building the foundation of a system's structure.

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    Class

    A class representing a physical or conceptual entity in a system, with attributes, operations, and associations. For example, the 'Flight' class represents a flight in a flight booking system.

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    Airport

    A class representing a physical location, typically an airport.

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    Airline

    A class representing a commercial entity involved in air travel, operating flights to different destinations

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    Abstract Class

    A class that is not fully defined and cannot be directly instantiated. It serves as a template for other classes and often contains abstract methods.

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    Object Diagram

    A visual representation of an object model, showcasing a snapshot of the system at a particular point in time.

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    Object Model

    A collection of objects where each object is an instance of a class within the class model. This represents a system's state at a specific moment.

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    Links in Object Diagram

    Objects connected in a diagram, representing specific cases of one object's awareness of another. They are instances of associations between classes.

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    Object Boxes in Object Diagram

    Rectangular boxes representing objects in an object diagram. They include the object name and its class name, along with optional attributes and values.

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    Generalization/Specialization

    A visual representation of the relationship between classes, showing generalization (parent-child relationship) and specialization (child's unique features).

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    Inheritance

    The process where a subclass acquires attributes and methods from a superclass, inheriting its characteristics.

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    Subclass

    A more specific class that inherits from a more general class, inheriting its characteristics and adding its own unique features.

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    Coincidental Cohesion

    A type of cohesion where the parts of a component are unrelated and perform independent tasks, leading to a messy design and potential difficulties in understanding and maintaining code.

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    Functional Cohesion

    The ideal type of cohesion where every essential element contributes to a single specific task. This means the code is clear, focused, and easy to understand and modify.

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    Sequential Cohesion

    A type of cohesion where elements within a component are sequentially related, meaning the output of one part becomes the input for the next. This is common in processes with a clear order of execution.

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    Communicational Cohesion

    A type of cohesion where elements within a component communicate with each other to carry out a single task, sharing data and information.

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    Procedural Cohesion

    A type of cohesion where elements within a component are grouped based on the procedures they perform, even if the procedures are unrelated. This can be less clear and harder to maintain.

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    Temporal Cohesion

    A type of cohesion where elements within a component are related because they need to be executed at a specific time or in a specific order, even if their functions are unrelated.

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    Logical Cohesion

    A type of cohesion where elements within a component are grouped based on a logical connection, even though their functions may be unrelated. This can create ambiguity and make code harder to understand and modify.

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    Study Notes

    Software Engineering 1 - Lecture 5

    • Lecture covers OO Modelling, UML Static Diagrams (Class, Object, & Package Diagrams)
    • Topics discussed include:
      • Continuing Class Diagrams
      • Associations
      • Multiplicity
      • Links and Associations
      • Roles
      • Self-Associations
      • Association classes vs. Ordinary classes
      • Qualified Association
      • A sample class model
      • Generalization, Specialization & Inheritance
      • Overriding Features
      • Abstract Class
      • Object Diagrams
      • Elements & An Example
      • Class Modeling Tips
      • Divide and Conquer: Modularization
      • Cohesion (Types of Cohesion: Coincidental, Functional, Coincidental)
      • Coupling (Examples and Consequences of Coupling)
      • Package Diagrams
      • Aggregation and Composition Relations
    • Associations are relationships between classes, indicated by a line with a name. Use verb phrases to name associations (e.g., "HasCapital").
    • An optional "reading direction arrow" can indicate reading direction.
    • There can be more than one association between classes.
    • Associations are usually implemented by a reference from one object to another
    • Associations are inherently bidirectional.
    • Associations can be unidirectional.
    • Multiplicity specifies the number of instances of one class (type) that may relate to a single instance of an associated class (type).
    • Multiplicity exposes hidden assumptions in the model.
      • An example is whether a person "WorksFor" one company or can work for multiple companies.
    • An association is a relationship between types that groups links
    • A link is a physical or conceptual connection among objects. Example: John works for GE company.
    • Roles are labels that are used to understand associations effectively, especially in self-associations. e.g., employee and employer in the relation WorksFor.
    • An association class is an association that is also considered a class (has attributes and operations). Example - Person OwnsStock Company. Purchase (has attributes and operations).
    • Many-to-many associations provide rationale for association classes.

    Object Diagrams - Elements

    • Object diagrams are visual representations of an object model, showing a snapshot of a system at a specific point in time.
    • Diagrams consist of rectangular boxes visually depicting objects.
    • Each box includes the object name followed by the class name (underlined).
    • Attribute names and values can be added inside the box (optional).
    • Lines connecting objects represent links; they show relationships between objects and are instances of associations.

    Class Modeling Tips

    • Scope: Model relevant aspects of a problem, ignoring irrelevant aspects.
    • Simplicity: Keep models as simple as possible; this aids understanding and development.
    • Diagram Layout: Arrange classes clearly and logically, avoiding crossed lines
    • Naming: Use meaningful and singular nouns for class names.

    Divide & Conquer: Modularization

    Modularization reduces system complexity by breaking it down into smaller parts with separate boundaries (modules). - Examples are whole programs, software libraries and classes (e.g., Java classes).

    • Modules should have good properties like maximal relationships within the module (cohesion) and minimal relationships between modules (coupling).
    • Decomposition can be through projection or partitioning.

    Cohesion

    Cohesion refers to the degree to which the components of a module are related to a single task. Types of cohesion differ in their level of functionality, with functional cohesion being the strongest and coincidental the weakest, and can be used for measuring internal glue of components.

    Coupling

    Coupling refers to the degree of dependency between modules. High coupling indicates a strong reliance between modules, while low coupling indicates a weaker reliance. High coupling makes understanding and modifying one module potentially affecting other modules, making it difficult to use or reuse. Conversely, low coupling makes modification easier.

    Package Diagrams

    Packages are used to organize large models for better understanding.

    • Models and classes can be grouped by their actors/relation.

    Aggregation/Composition

    • Aggregation is a special type of association where objects are part of a larger object.
    • Composition is a stronger form of aggregation where the existence of a part depends on the existence of the whole.

    Generalization, Specialization, and Inheritance

    • Generalization is a type of relationship between a class, the superclass, and one or more variations of the class, called a subclass.
    • The superclass holds the most common attributes and associations among subclasses.
    • Subclasses inherit features of the superclass and can add specific attributes and associations, refining the superclass.
    • Inheritance is frequently referred to in terms of an "is-a" relationship.
    • Generalization is transitive across an arbitrary number of levels (class relationships are transitive)
    • An "ancestor" is a class that is a parent or grandparent class of another class
    • A "descendant" is a class that is a child or grandchild class of another class.

    Abstract Classes

    An abstract class is an incomplete class.

    • It cannot be instantiated and serves as a base class which allows other classes to inherit or specialize its functionality (e.g., Employee with subclasses FullTimeEmployee and PartTimeEmployee).

    Object Diagrams

    Object diagrams represent a snapshot of the system at a specific time. - They have boxes referring to objects, and lines to connect the association/relation between the objects

    • Every object in a diagram must be an instance of one of the classes in the class model.

    Additional Notes

    • The order of modeling is define classes, define associations and define multiplicity.
    • Models show classes in a flight system, including passengers, seats, airplane, pilot, co-pilot and airlines, for representing connections (from, to, has, runs, uses).
    • Adding suitable attributes and operations to the flight model classes is an important part of the modelling.

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    Test your knowledge on UML class diagrams focusing on associations, qualified associations, and their characteristics. This quiz covers fundamental concepts necessary for modeling relationships in UML, particularly in complex scenarios like many-to-many relationships. Join to discover more about proper naming and functionalities of these critical components.

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