Questions tagged [entity]
An entity is an object or a set of data that has an identity that persists changes of its attributes. In an object oriented context, it usually refers to long-lived information relevant for the stakeholders of the system.
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Dilema about having a Country, Province, City model separate Aggregate or in the same aggregate
We are porting an old monolith application and we are trying to apply the DDD concepts, we started looking for what we think are the Bounding Contexts of the application.
We have what we thought would ...
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determine correct relations in ERD - Customer Orders use case
The below ERD is taken from a professional architecture reference, however I have a concern in the relation between Customer and Invoice, I believe that relation between Customer to Order , and Order ...
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ER Diagram - How to display relationships between Entities that are a type of another
I face a problem in understanding how this situation can be traduced to an ER diagram.
So I have an entity, let's call it car, and then, there are another entities, that are a type of car. For example,...
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Splitting nested entities keeping invariant within aggregates
I'm currently developing message imap-based module in crm app and i'm trying to connect dots using ddd principals.
I've started with three main entities, all bound under Account Aggregate:
Account - ...
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Clean Architecture, what are objects that does not completely fit as entities?
I'm reading chapter 20, "Business Rules", of clean architecture book, in this chapter Uncle Bob defines entities as:
An Entity is an object within our computer system that embodies a
small ...
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DDD Modeling - Entity with generic and specific data
Suppose I am buying coffee. There are several types of coffee (A1, A2, A3), but sometimes I want to make a reference to all types of coffee (like if I had a coffee "grouped"). Considering ...
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Dealing with business logic on DTOs using a DDD
I have a scenario in which an Entity defines an EntityRepresentation that is created from another end. The EntityRepresentation is a value object that implements some logic that should be performed on ...
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DDD Best way to preserve integrity of entity
I have an entity that contain the status of data (WaitingForData, ReadyForData, DataUsed).
class Batch
{
int Status { get; }
DateTime StartTime { get; }
string Code { get; }
void ...
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When to use entity and when to use DTOs
Hi I am very new to using DTOs, and I am starting to understand it slowly, but there are still some missing puzzles for me.
I understand the use of DTOs in the way of decoupling the persistence data ...
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Modeling a workout schedule using OOP(DDD specifically)
I am just getting into DDD, and I am trying to model a very basic exercise schedule. I have a Schedule and I have a Slot the slot takes 0 - many Exercise entities. The schedule is composed of Slots ...
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Should entities contain information about their amount?
Can I get some thoughts on the entity design?
Let's say I have an entity called Book. Let's say I create a specific instance of that book. It has a title A and an author B. Since there can be multiple ...
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How to change a data model
In my model a user entity has three attributes : ID, name, hasBoyfriend.
I want now to change hasBoyfriend to boyFriendsNames which is an array of names .
The user entity is used by many services.
The ...
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Relationship between entities in different aggregates and size of aggregate
I read a lot about DDD but few thing are still unclear. At this moment I have two dilemma
The size of aggregates. How small could be an aggregate?
For example we have:
class Car {
String colorId
...
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Database Design: Storing price date wise, or date range wise?
I must store prices for various items on multiple dates. The table schema would look like this:
CREATE TABLE date_wise_price (
item_code varchar,
date date,
price numeric(19,4)
)
An ...
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What is proper approach to code first entity relationship design?
I been trying to figure out, what i hoped is a simple problem, but am yet to land with an answer.
How do you go about designing an entity relationship diagram when doing code first development?
The ...
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Entity delete validation in a microservice environment
In a microservice environment there are two services: Service A and Service B.
Service A manages an entity called x which has one to many relationship with service B's entity called y
When a network ...
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How to decide on abstraction level and entity definitions?
I am working on a hobby project of mine where I want to make an application to doing my personal finances. Just for learning. I am trying to adhere and implement best practices and patterns to learn ...
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Can I put domain services inside domain entities?
Say I have a domain entity User:
class User {
constructor (username, email, password) {
this.username = username
this.email = email
this.password = password
}
}
Now, all users need a ...
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Best practice for references in DTOs and entities in Spring
Given the following architecture and frameworks:
Spring Boot Application with Spring Data JPA (Hibernate is used as OR mapper); layered architecture as followed.
REST layer
Service layer
Persistence ...
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Why can't Entities leave the inner layers in the Clean Architecture?
I was reading about the clean architecture, and I don't get this part:
Don't use your Entity objects as data structures to pass around in the outer layers. Make separate data model objects for that.
...
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Need for a domain model in a service in 3 tier architecture?
I am building an API Rest with Spring Boot and I would like to clarify a concept about my architecture, to see if the community can help me.
Imagine that in my database I have a table called Person. ...
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DDD Value Objects and Entity Without ORM Mapping in PHP
First, as I know, Entity in DDD is almost same with Value Object except Entity has identity. Every article I have read say same thing that entity id has ORM mapping with any ORM tool. But I don’t want ...
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Changing entities in Clean Architecture
I'm modeling the "Domain" Layer of "Clean Architecture" for an application that gets its data from an XML file when starts.
The XML file looks like:
<?xml version="1.0" encoding="UTF-8" ?>
<...
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When to model an aggregate's entities as part of a value object?
I've read a lot about Domain Driven Design including books from Eric Evans and Vaughn Vernon. So I am familiar with the concepts Aggregate Root, Entity, and Value Object.
But while I was modeling ...
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Domain vs Entities model? Domain-Driven-Design (DDD)?
In this github, https://github.com/johnph/simple-transaction, under the Transaction.Framework project, there are entities (located at Data/Entities)
AccountSummaryEntity.cs
AccountTransactionEntity
...
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What is optimal number of entity abstraction levels?
Sorry about the vague question, please do suggest different formulations. Anyway here is the kernel of the question:
How many classes representing an entity/resource or whatever you want to call it, ...
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How to prevent concurrency problems when using the repository pattern?
Considering that:
when using the repository pattern you deal with entities - those are the atomic units you persist (regardless of Hibernate or "manually")
when changing an entity you save it as a ...
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Aggregate root being created by multiple other aggregate roots
I know the title is confusing, I didn't how to word it.
I'm studying the Domain Driven Design (DDD) and I'm reading the book "NET Microservices Architecture for Containerized NET Applications" from ...
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Can we have a ternary relationship together with a recursive one in E-R diagrams
I am designing an E-R Diagram for a simple system where there are some users and contests. A user can create a contest or invite other users to the contest who can decide to accept or not.
I am ...
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How to determine aggregates when entities are shared?
So I'm trying to figure out exactly what my aggregates/aggregate roots are in my structure, and can't seem to wrap my head around it.
Database contains the following tables:
SALESGROUP
ID
...
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Depend on DDD Entities or Interfaces?
My understanding is that the dependency inversion principle does not apply to entities, because entities basically are your application - it generally doesn't make sense to swap out a different ...
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What is DDD's concepts mapping to microservice's concepts? [closed]
DDD concepts: Domain, Aggregate, Entity, Value object, Bounded context
Should every aggregate be a single microservice and have a single DB
( since every microservice should have a single specific DB)...
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Do menu option lists (and similar labels) belong in the database?
I am moving in the direction from database-centric design to entity-centric design (say, starting with class definitions instead of starting with a ERD), and am questioning things:
Often in a ...
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Repository pattern usage
I need some advice regarding repository pattern. Let's assume i have UserBal which stands for business logic which uses UserRepositoryDal where all database logic for that entity stands (queries to ...
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Using the same entity for different use cases
Suppose I have a User entity with name and age attributes. A User can own Boxes. A Box has the name and color attributes. Business rules dictate that one User can own at most 5 boxes. So, in this case,...
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Domain models vs entity models vs Hibernate lazy loading
In a new Java project I plan to use an extra layer above Hibernate entities. So there would be a CustomerEntity and CustomerDomain. The reason for that is that the CustomerDomain can contain extra ...
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Modify a property of an aggregate's entity
Suppose I have a house-lending service, like Airbnb. I have a House entity, which can have a name. There's also the Reservation entity, which has a start date, an end date, and a name (which isn't ...
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ER diagram - feasibility of a requirement
I need to model the following requirement in an Entity-Relationship diagram.
"Customers place orders, which contain a list of products with their quantity and prices. A shipment is made when ...
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Is a repository return a graph of entities violating SRP?
I'm working in this scenario
Post entity has many Image entities.
I also have repository to both entities:
PostRepository
ImageRepository
Since this entities are tightly related, when I get a Post ...
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Delete dependent entities
I have a temporary report table which has a foreign key (source_id), e.g. report table:
| id | val1 | val2 | source_id |
| -- | ---- | ---- | --------- |
| 1 | 102 | 0.5 | 1 |
| 2 | 99 |...
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How to set nullable/optional property of database object to NULL in backend?
We are building API which mainly passes database objects back and forth between user and database, so the main flow of information is quite basic:
Table (view) <-- ORM --> C#/Java/etc. Objects &...
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When converting the ER into the class diagram, what happened to the Weak Entities in the ER diagram
I am trying to convert an ER diagram into a class diagram. Below image is showing that part of my ER diagram and which contains a weak entity call 'Parent'. Therefore when we consider the ER diagram, ...
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Business Logic Entities and Data Access Layer Entities
I am thinking on how to structure a project. I wonder if it is a good practice to use different entity classes between the BL and DAL in order to decouple these layers.
I have worked on projects ...
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Updating entity with REST
I'm looking for the "Holy Grail" (best practise) of how to update an entity with REST?
There are three main approaches I've found so far:
Always send full entity, regardless what has been changed ...
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Should entity properties be represented by a value object?
I read somewhere that one should be generous in creating value objects for entity properties that are part of the class API.
So I did that with my project entity/aggregate, but it still looks weird:
...
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PHP: Domain model and aggregates
I am building an app that uses a client and a project entity.
The clients can extend their profile over various screens in their account, like status, settings, etc. These data sets are saved in ...
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Best way to handle environment specif fields in Hibernate
We have one microservice that will be deployed on two different environments(A and B). There are some common fields and also some are specific to the environment.
Example:
SomeEntity for environment ...
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Should i use an abstract class or an interface for my doctrine model?
In Doctrine, assuming I want to implement different types of vehicles. Maybe a car, a plane, a bicycle and so on ... all these vehicles have many different properties but also very common things like ...
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DDD - delegate business rule of domain object to external service
Situation:
I am implementing DDD in my first project and I would like to clarify how to correctly implement strategy pattern (in my case check if API token is active). This is a business rule of ...
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What is the use of DTO instead of Entity?
I am working on RCP application, I'm new to this application.
Spring beans are used to write business logic to save/fetch entities.
But, instead of sending entities directly to client we are ...
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