ConceptModelling
COMP2511
Domain Modelling
using UML
Prepared by Dr. Robert Clifton-Everest
Updated by Dr. Ashesh Mahidadia
Domain Models
• Domain Models are used to visually represent important domain concepts and
relationships between them.
• Domain Models help clarify and communicate important domain specific concepts and
are used during the requirements gathering and designing phase.
• Domain modeling is the activity of expressing related domain concepts into a domain
model.
• Domain models are also often referred to as conceptual models or domain object models.
• We will be use Unified Modeling Language (UML) class diagrams to represent domain
models.
• There are many different modelling frameworks, like: UML, Entity-Relationship, Mind
maps, Context maps, Concept diagrams. etc.
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Requirements Analysis vs Domain modelling
• Requirements analysis determines external behaviour
“What are the features of the system-to-be and who requires these features (actors) ”
• Domain modelling determines (internal behavior) –
“how elements of system-to-be interact to produce the external behaviour”
• Requirements analysis and domain modelling are mutually dependent – domain
modelling supports clarification of requirements, whereas requirements help building up
the model.
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What is a domain?
• Domain – A sphere of knowledge particular to the problem being solved
• Domain expert – A person expert in the domain
• For example, in the domain of cake decorating, cake decorators are the domain experts
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Problem
A motivating example:
• Tourists have schedules that involve at least one and possibly several cities
• Hotels have a variety of rooms of different grades: standard and premium
• Tours are booked at either a standard or premium rate, indicating the grade of hotel
room
• In each city of their tour, a tourist is booked into a hotel room of the chosen grade
• Each room booking made by a tourist has an arrival date and a departure date
• Hotels are identified by a name (e.g. Melbourne Hyatt) and rooms by a number
• Tourists may book, cancel or update schedules in their tour
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Ubiquitous language
• Things in our design must represent real things in the domain expert’s mental model.
• For example, if the domain expert calls something an “order” then in our domain model
(and ultimately our implementation) we should have something called an Order.
• Similarly, our domain model should not contain an OrderHelper, OrderManager, etc.
• Technical details do not form part of the domain model as they are not part of the
design.
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Noun/verb analysis
• Finding the ubiquitous language of the domain by finding the nouns and verbs in the
requirements
• The nouns are possible entities in the domain model and the verbs possible behaviours
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Problem
• The nouns and verbs:
• Tourists have schedules that involve at least one and possibly several cities
• Hotels have a variety of rooms of different grades: standard and premium
• Tours are booked at either a standard or premium rate, indicating the grade of
hotel room
• In each city of their tour, a tourist is booked into a hotel room of the chosen grade
• Each room booking made by a tourist has an arrival date and a departure date
• Hotels are identified by a name (e.g. Melbourne Hyatt) and rooms by a number
• Tourists may book, cancel or update schedules in their tour
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UML Class diagrams
• Classes
• Relationships
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UML Class diagrams
• The loosest form of relationship. A class in some way depends on another.
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• A class “uses” another class in some way. When undirected, it is not yet clear in what
direction dependency occurs.
• Refines association by indicating which class has knowledge of the other
UML Class diagrams
• A class contains another class (e.g. a course contains students). Note that the diamond it
at the end with the containing class.
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• Like aggregation, but the contained class is integral to the containing class. The contained
class cannot exist outside of the container (e.g. the leg of a chair)
UML Diagram Types
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Examples
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Representing classes in UML
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Representing classes in UML
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Representing classes in UML
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Representing Association in UML
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Representing Association in UML
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Representing Association in UML
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Attributes vs. Classes
• The most common confusion – should it be an attribute or a class?
• when creating a domain model is to represent something as an
attribute when it should have been a conceptual class.
• If a concept is not representable by a number or a string, most likely it
is a class.
• For example: a lab mark (attribute) vs a student (class)
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Attributes vs. Classes
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(From https://homepages.fhv.at/thjo/lecturenotes/sysan/domain-modeling.html#attributes-vs.-classes)
What wrong with the following?
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A Possible solution
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References
• A very detailed description of UML
• https://www.uml-diagrams.org/
• Books that go into detail on Domain Driven Design
• Domain-Driven Design: Tackling Complexity in the Heart of Software by Eric Evans.
• Domain Modeling Made Functional: Tackle Software Complexity with Domain-Driven
Design and F# by Scott Wlaschin.
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https://www.uml-diagrams.org/