What is Domain Model and Conceptual Classes?. Tutorial

Summary

In this educational video, the presenter introduces the concept of domain models, focusing on their role in software design. Using UML class diagram notation, the video explains the difference between conceptual classes and software artifacts, emphasizing that domain models should reflect real-world entities and relationships, not software-specific constructs. The script guides viewers through creating a domain model, illustrating how to define conceptual classes, their attributes, and associations. It also highlights common mistakes, such as confusing attributes with classes, and provides examples to clarify these concepts, aiming to enhance understanding of domain modeling in software development.

Takeaways

• 😀 Domain models are visual representations of conceptual classes, distinct from software classes.
• 📚 The video introduces chapter nine focusing on domain models, starting with an example in Figure 9.1.
• 📊 Figure 9.2 illustrates a partial domain model using UML class diagram notation, highlighting attributes and associations.
• 🔗 Associations in domain models are represented by lines linking classes, indicating relationships between them.
• 🚫 Domain models exclude software artifacts to focus on real-world concepts, such as 'sales database' being a software artifact, not part of the domain model.
• 💡 Conceptual classes are ideas, things, or objects, and are the building blocks of a domain model, representing real-world entities.
• 🎯 The purpose of a domain model is to understand the vocabulary and key concepts of a system, facilitating better system comprehension.
• 🛠️ To create a domain model, one should identify conceptual classes from different categories and represent them with attributes and associations.
• 📝 An important guideline is to differentiate between attributes and classes to avoid common mistakes, ensuring clarity in the model.
• 🔍 The video provides examples and guidelines on how to correctly represent relationships and avoid misrepresenting real-world entities as software artifacts in domain models.

Q & A

What is the main topic of chapter nine in the video?

The main topic of chapter nine in the video is 'Domain Models'.

What is the difference between a domain model and a class diagram?

In a domain model, only attributes are shown, while a class diagram includes both attributes and operations or methods.

What are the lines and links between classes in a domain model called?

The lines and links between classes in a domain model are called associations.

What is a domain model according to the video?

A domain model is a visual representation of conceptual classes, also known as conceptual models.

Why are software artifacts not included in a domain model?

Software artifacts are not included in a domain model because a domain model represents real-world concepts, not software classes or artifacts.

What is a conceptual class?

A conceptual class is an idea, thing, or object that is abstract and not tied to software implementation.

What are the three key elements of a conceptual class mentioned in the video?

The three key elements of a conceptual class are intension, extension, and identification.

Why do we create a domain model?

We create a domain model to understand the vocabulary and key concepts of a system and to get a better understanding of the system.

How can conceptual classes be identified from different categories?

Conceptual classes can be identified from different categories by looking at examples like sales, payments, reservations, and other real-world scenarios.

What is the guideline for creating a domain model?

The guideline for creating a domain model involves identifying conceptual classes, giving them attributes, and creating associations between them using UML class diagram notation.

What is a common mistake when creating a domain model?

A common mistake when creating a domain model is confusing attributes with classes, which should be clearly separated.

Outlines

00:00

📚 Introduction to Domain Models

The video begins with a warm welcome to the YouTube channel and introduces Chapter 9 on Domain Models. The speaker explains that domain models are visual representations of conceptual classes, which are distinct from software classes. An example of a partial domain model is given, depicted using UML class diagram notation. This notation includes attributes and operations or methods, but domain models focus solely on attributes and their associations. The speaker emphasizes that domain models are conceptual and do not include software artifacts, using 'sales database' as an example of something that would not be part of a domain model. The importance of understanding domain models for representing real-world situations is highlighted.

05:06

🌐 Understanding Conceptual Classes

Paragraph 2 delves into the concept of conceptual classes, which are ideas, things, or objects that form the basis of domain models. The speaker clarifies that domain models are graphical representations of real-world concepts and are not related to software artifacts. The paragraph distinguishes between conceptual classes and software classes, using 'gender' and 'age' as examples of attributes that can be part of a domain model. The speaker also discusses the intention behind conceptual classes, explaining that they are defined by their name, phone number, age, and address. The paragraph concludes with an emphasis on the importance of conceptual classes in creating a domain model for a better understanding of the system.

10:07

🛠 Creating a Domain Model

Paragraph 3 discusses the process of creating a domain model, starting with identifying conceptual class categories and their examples, such as 'sale', 'payment', and 'reservation'. The speaker explains that these conceptual classes can act as candidates for inclusion in a domain model. The paragraph also touches on the importance of understanding the vocabulary and key concepts of a domain model for system comprehension. The speaker provides a guideline on how to create a domain model, suggesting that one should start by identifying conceptual classes from different categories and then proceed to draw them using class diagram notation, focusing on attributes and associations.

15:10

🎯 Sketching Domain Models with UML

In Paragraph 4, the speaker demonstrates how to create a domain model using UML class diagram notation. The process involves identifying classes such as 'line item', 'item register', 'ledger', 'cashier', 'customer', 'store', 'product description', and 'product catalog'. The speaker corrects a mistake made in the initial sketch, emphasizing the importance of accurately representing relationships and attributes. The paragraph also discusses the common mistake of confusing attributes with classes, using 'airport' as an example to illustrate the correct approach. The speaker concludes by emphasizing the use of UML for sketching domain models in agile modeling.

20:17

🔍 Correcting Mistakes in Domain Model Attributes

Paragraph 5 addresses common mistakes in domain model creation, particularly the confusion between attributes and classes. The speaker uses the example of 'product description' and 'item' to illustrate how they should be correctly represented in a domain model with a one-to-many relationship. The paragraph also discusses how to improve the representation of a domain model, suggesting that a better approach is to clearly define the relationships and attributes. The speaker provides examples from figures 9.10 and beyond to show how descriptions and relationships should be correctly depicted in a domain model.

Keywords

💡Domain Model

A domain model is a conceptual model that represents the structure and behavior of the problem domain. It is a visual representation of conceptual classes, which are abstract representations of real-world concepts. In the video, the domain model is discussed as a way to understand the vocabulary and key concepts of a system, and it is depicted as a UML class diagram that shows classes, their attributes, and associations without including methods or software artifacts.

💡UML Class Diagram

UML (Unified Modeling Language) class diagrams are a standard way of representing static structure of a system. They show classes, their attributes, operations, and the relationships between objects. In the context of the video, UML class diagrams are used to draw domain models, focusing on attributes and associations, but excluding operations, as the domain model is more concerned with the conceptual structure rather than the implementation details.

💡Conceptual Classes

Conceptual classes are abstract representations of real-world entities or ideas. They form the basis of a domain model and are used to capture the essence of the problem domain without getting into the specifics of software implementation. The video emphasizes that conceptual classes in a domain model represent real-world situations and concepts, such as 'Sale' or 'Customer', and are distinct from software classes.

💡Associations

In UML class diagrams, associations are lines that link classes and represent relationships between them. The video script explains that these lines, or links, are called associations and are a key element in domain models. They show how different conceptual classes are connected, which is crucial for understanding the structure of the domain.

💡Attributes

Attributes in a class diagram are properties or characteristics of a class. The video script mentions that in a domain model, classes have attributes but not operations or methods. Attributes help define the characteristics of conceptual classes, such as 'name', 'phone number', 'age', and 'address' for a 'Customer' class.

💡Software Artifacts

Software artifacts are elements that are part of the software implementation, such as databases, user interfaces, or code. The video script clarifies that domain models should not include software artifacts because they represent the real-world concepts, not the implementation details. For example, a 'Sales Database' is a software artifact and should not be part of a domain model.

💡Conceptual Class

A conceptual class is an abstract representation of an idea, thing, or object in the problem domain. The video script provides examples of conceptual classes, such as 'Sale', 'Payment', and 'Reservation', and explains that these classes are used to build the domain model. Conceptual classes are the building blocks for understanding the domain and are distinct from the actual software classes that might implement them.

💡Multiplicity

Multiplicity in UML class diagrams indicates the number of instances one class can have in relation to another. The video script uses a star symbol to denote multiplicity, showing how many instances of one class are associated with an instance of another class. For example, a 'Product Description' might be associated with many 'Items', indicating a one-to-many relationship.

💡Agile Modeling

Agile Modeling is a set of best practices for modeling and documentation in an agile project. The video script mentions that agile modeling uses UML diagramming notation, which is why UML class diagrams are used to sketch domain models in an agile context. Agile Modeling emphasizes flexibility and adaptability, which is reflected in the iterative and incremental nature of creating domain models.

💡Common Mistake: Attributes vs. Classes

The video script highlights a common mistake of confusing attributes with classes. Attributes are properties of a class, while classes represent entities or concepts. The script provides an example of this mistake, where 'Airport' is incorrectly treated as an attribute instead of a class. The correct approach is to treat 'Airport' as a class with attributes like 'name' and 'destination'.

Highlights

Introduction to chapter nine on domain models.

Definition and discussion of domain models as conceptual models.

Explanation of the difference between domain models and class diagrams, including the inclusion of operations in class diagrams.

Description of associations in domain models as connections between classes.

Emphasis on the importance of remembering that methods are not included in domain model classes.

Clarification that domain models represent real-world concepts, not software artifacts.

Discussion on the exclusion of software-related classes from domain models.

Definition of conceptual classes as ideas, things, or objects.

Explanation of the three aspects of conceptual classes: intension, extension, and conceptual symbols.

Purpose of creating domain models for understanding vocabulary and key concepts of a system.

Guidelines on how to create a domain model using UML class diagram notation.

Common mistake clarification between attributes and classes in domain models.

Example of correctly associating conceptual classes in a domain model.

Discussion on the importance of correctly identifying conceptual classes for domain modeling.

Agile modeling's use of UML diagramming notation for sketching domain models.

Final thoughts on the practical application of domain models in understanding system concepts.

Transcripts

assalamualaikum viewers welcome to our

youtube channel

today the chapter that we are going to

start is chapter number nine that is

domain models

so first we will discuss what is domain

models so let's first discus

example that is 9.1 we say that figure

9.2 shows a partial domain model drawn

with uml class diagram notation

diagram so

diagram you don't know

in domain model we have just attributes

but in class diagram we have attributes

along with operations or methods

fine so again

now you can see this figure figure 9.2

what is happening in this domain model

we are having some of the classes

and there is some association in between

them these

lines and links are actually called

associations

fine we can see these relationships

concepts

so these are the attributes here this

line is

actually called association it is also

told here fine

so these are the things to be noted and

remember that methods are not

included in these classes as these are

conceptual classes

and when we combine all the conceptual

classes we get a domain model

okay so what is a domain model a domain

model is a visual representation of

conceptual classes

or

can also be called conceptual models so

it means if somebody asks you

or if you come across a multiple choice

question like

top secret domain model conceptual model

domain object model yeah analysis object

model be here

okay so you can see figure 9.3 here a

domain model shows

real situation conceptual classes not

software classes

the real situation the conceptual

classes could represent software classes

could represent

[Music]

[Music]

say real world concepts are related some

guests are thinking a real world

situation

a real situation conceptual classes

representation

visualization a graphical representation

has so this is a domain model

next remember 9.4 a domain model does

not show software artifacts or classes

software's related to software artifacts

you can see this in this diagram like we

are going to avoid such

classes first one sales database

what does this mean yex software

artifact it is not a part of domain

model why

is sales database

[Music]

gender and age like that

so this can't be a part of a domain

model as it is a software artifact

next is

it is fine it is perfect but we are

talking about domain model

this is a software class we can't

include it in the domain

[Music]

this is a conceptual class okay okay so

next we are having is

definition what are conceptual classes

conceptual classes

basically conceptual class is an idea

thing or object

simply conceptual class

objective

[Music]

if we talk about intention we said that

it is the definition of conceptual class

a definition they are in the basic

definition

let's take another example

it has name phone number age and address

job attributes some include classmates

there has a concept intention or tia

pass what is the concepts

extension you could example something

like sale one sale to sell three sale

three things that we discussed regarding

conceptual classes concept

symbol intention and extension

making a general

so this is the reason of creating the

main model so that

we can get the understanding of

vocabulary key concepts

and also to get better understanding of

the system let's discuss

an important guideline that is how to

create a domain model

hum of domain model could create

questions

then we discussed why do we create a

domain model and now we are going to

discuss

here so you can see here that from these

conceptual class categories we are

getting some of the examples like

sale payment reservation yes sales line

similarly from other conceptual class

categories we are getting

different examples find

different classes like a place of

transaction your place of service so to

store

transactions at the airport plane see

these all can be our conceptual classes

from these type

[Music]

foreign

scenario here

as conceptual classes they can act as a

candidate

customer also appears check out also

goods services

cashier sale item identifier sale line

item item description price total taxes

payment accounting sales again

commissions inventory

and many more the case 7 i was received

so these all can be what these can be

our

conceptual classes candidate conceptual

classes like

these all can be our candidate

[Music]

sale line item or amount rendered

classes identification one two three

four five six

and all our next job is what

we have to draw conceptual

line item item register ledger cashier

customer store product description and

product catalog

correct list simply domain model created

simply

through class diagram notation okay so

like this you will complete all of the

classes

only attributes after giving

sorry let's correct it after giving

attributes here we are going to make

associations as well

attributes associations create

like this we can give a star here

that indicates multiplicity so this is

what

association is there

same is the case here for monopoly

domain same

value identification then you are going

to make classes

afterwards we can see these are six

classes here

i'm gonna identify here i'm gonna draw

here further we also

let's check them no it's enough you have

my personal six classes he identified

scenario like monopoly game player

piece board square and diet classes

giant modeling sketching a class diagram

we already

read that agile modeling uses uml

diagramming notation

so that is why we use uml class diagram

for sketching agile modeling

okay okay now let's discuss an important

topic that

is guideline a common mistake with

attributes versus classes

common mistake attributes or classes

let's see an example is here

that is discussed

separate

[Music]

then we will come to know about it okay

so airport is

another conceptual class that is having

some separate

attribute like name in the real world

destination airport is not considered a

real world

okay let's see these associations

that is not right this is worse we

should make something

else so this is a better one like a

product description

description and we are having

a conceptual class that whose name is

item

uh attribute has serial number now

they can have a one-to-many relationship

easily the egg product description

against

maximum any many items

so this is a better approach let's see

some particular figures

like figure 9.10 description about other

things

the other things

flight

this is worse but this is better how is

it better

let's see flight is being described

description

you