Questions tagged [entity]

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4
votes
2answers
477 views

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 ...
3
votes
4answers
349 views

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, ...
6
votes
1answer
214 views

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 ...
1
vote
1answer
108 views

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 ...
2
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1answer
49 views

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 ...
0
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1answer
94 views

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 ...
1
vote
1answer
106 views

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 ...
-3
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2answers
263 views

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)...
0
votes
1answer
58 views

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 ...
4
votes
2answers
286 views

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 ...
0
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1answer
71 views

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,...
2
votes
2answers
285 views

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 ...
0
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1answer
167 views

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 ...
2
votes
2answers
86 views

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 ...
4
votes
3answers
181 views

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 ...
0
votes
1answer
60 views

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 |...
1
vote
1answer
96 views

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 &...
1
vote
2answers
319 views

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, ...
3
votes
3answers
3k views

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 ...
-1
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1answer
291 views

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 ...
0
votes
1answer
205 views

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: ...
1
vote
1answer
274 views

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 ...
0
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1answer
59 views

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 ...
0
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2answers
943 views

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 ...
3
votes
2answers
704 views

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 ...
17
votes
1answer
23k views

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 ...
4
votes
1answer
382 views

DDD: How to work with entity variations?

Let's say I have an Entity that represents an employee: Employee First name Last name Birthdate Hair color Eye color Gender .... (and so on) Now, imagine I have a website ...
4
votes
1answer
7k views

Data Objects for each layer(DTO vs Entity vs Response objects)

Let's say I'm building a Customer web application(in Spring Boot 2), which also exposes rest end points. I'm modeling my application into 3 layers. a) UI - CustomerDTO b) REST - ...
1
vote
1answer
267 views

Imposing conditional entity relations

While working on an application, I am facing an issue. And I am not sure how to solve this. For explanation I have managed to come up with a simple example below: Consider a Grocery Store ...
5
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5answers
1k views

Why is the ampersand (&) a HTML Entity?

I understand the rationale behind why most of the HTML character Entities were created, but I don't understand the purpose behind the ampersand HTML entity. &amp; contains more bits than a & ...
0
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1answer
1k views

What is the best practice for API endpoints for an entity?

I don't know if the title is reflecting the question correctly, but I can explain more than write a good title. If I have a database that has (employees, departments, orders, etc...), and have ...
3
votes
1answer
1k views

Is it normal for a Domain Model not to have an ID?

After reading the book; I understood the following: 1) Entities should implement equality and compare by ID. 2) Value Objects should implement equality and compare by all properties in the class. I ...
2
votes
2answers
79 views

Sql: Pre inserting relational entities vs the “lazy creation” of the entities

I have the following entities in my database (it's simplified): Student (id) StudentCourse (id, student_id, course_id) Course (id) Lesson (id) LessonCourse (id, lesson_id, course_id) ...
4
votes
1answer
6k views

Shall the Database in a sequence diagram be represented as actor or boundary?

I'm designing a system made of a web application and database. I use the <<Entity>> - <<Control>> - <<Boundary>> stereotypes in my UML diagram. In the following ...
-2
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1answer
151 views

Filling in background information in terms of DDD

Recently, I asked about my difficulties in finding the boundaries of aggregates here and I recently reinterpreted it and rid it of business features and now it sounds like this: In many sources, ...
10
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2answers
2k views

How to design the aggregate boundaries?

I would like to write an application something like ecommerce. And you know that in similar applications products could have different properties and features. To simulate such an opportunity I've ...
4
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1answer
670 views

DDD - Domain Modelling association between aggregates

I have a bit of a mental block when trying to model my scenario whilst practicing DDD. The problem appears to be around 2 entities you would consider to be aggregate roots. I feel these aggregate ...
1
vote
1answer
1k views

Service layer with DTO

I'm refactoring my desing to use a service layer - however I'm confused about how you would pass arguments, when it's only allowed to update certain fields of the entity. For instance I have some ...
0
votes
4answers
391 views

The Open/Closed Principle, how does it work for adding entities?

I'm not even sure how to ask this, but here goes: Let's say I have a Web application that incorporates Teachers, Courses and Students in such a way that I can do things like this (pseudocode): ...
2
votes
4answers
3k views

ASP.NET Projects using too much .NET Boilerplate Libraries / Code

I am very puzzled with the obsession that many people seem to have with using Microsoft frameworks. I have seen several tutorials and projects (both open and closed source) that seem to utilize all of ...
0
votes
1answer
3k views

How to represent and validate website URLs for a JPA entity

I have an application that will allow the user to enter and store (in a DB) a website URL for a company. The only requirement (as of now) beyond entry of the website URL is to validate that the URL is ...
1
vote
2answers
848 views

How to really decide whether an entity is weak or not

This is the ER diagram example from the Wikipedia. Here they have marked the Orders entity as a strong entity. As I understand a weak entity is an entity which cannot exist without a corresponding ...
-1
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4answers
95 views

Is there a term for an entity that represents another known missing entity?

I am working on a project where I am importing data from 3rd party sources. Often certain data is missing (usually older data), which is detectable from the data that I do have. Obviously I cannot ...
1
vote
2answers
101 views

Dealing with entities customization

I suppose every project that is considered as huge and diversed into a lot of parts (admin side, widgets, API, website with a lot of stuff and management) can finally encounter that it is actually ...
0
votes
1answer
930 views

Should I extend an entity object with a separate class?

I have a simple entity class in my C# application that I would like to add additional properties to for use in the app. These properties will not be persisted to the database. In the past, I was ...
5
votes
2answers
921 views

A more data oriented design approach to Entity Component System

I'm creating my first c++ game engine project (for learning purposes) and in it I've attempted to implement an entity/component system utilizing some data oriented design principles while also not ...
10
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2answers
4k views

How to create new aggregate root in CQRS?

How should we create new aggregate roots in cqrs architecture? In this example I want to create new aggregate root AR2 that holds reference to first one AR1. I'm creating AR2 using AR1 method as ...
4
votes
2answers
1k views

is it bad practice that controller call domain objects(entities) direclty instead of service?

is it bad practice that controller call the methods of domain objects directly instead of service? to explain more: I figure out that in good design controllers call service and service use Domain ...
2
votes
1answer
548 views

Configuring entity behavior DDD

In one of the products I work with we have an aggregation root with a lot of domain logic, and now I have a requirement to make one small piece of behavior configurable. To give an example, let's say ...
5
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1answer
280 views

Should I retrieve related entities from the parent entity or the service layer?

Let's say I have a three tier application structure, with Presentation, Service and Data layers. The data layer is managed by an ORM and has two models/entities, Show and Episode, with a one-to-many ...