Glossary

A

  • ACL - See Anti Corruption Layer.
  • Aggregate - A cluster of associated objects that are treated as a unit for the purpose of data changes. External references are restricted to one member of the Aggregate, designated as the root. A set of consistency rules applies within the Aggregate’s boundaries.
  • Aggregate root - Gatekeeper object for the aggregate. All access to the objects within the aggregate must occur through the aggregate root; external entities are only permitted to hold a reference to the aggregate root.
  • Anti Corruption Layer - Anti-corruption Layers help protect against corruption in the domain model when the system interacts with other systems or bounded contexts. The Anti-corruption Layer translates to and from the other system’s models. It is often implemented using the Facade and/or Adapter design pattern.
  • Analysis pattern - A group of concepts that represents a common construction in business modeling. It may be relevant to only 1 domain or may span many domains (resource fowler 1997, p. 8)
  • Application Layer - Manage transactions, coordinates application activities, creates and accesses domain objects.
  • Application Service - Used by external consumers to talk to your system. If consumers need access to CRUD operations, they would be exposed via a application service. Application Services will typically use both Domain Services and Repositories to deal with external requests.
  • Assertion - A statement of the correct state of a program at some point, independent of how it does it. Typically a Assertion specifies the result of an operation or the required input for and operation.

B

  • BC - See Bounded Context.
  • Bounded Context - A division of a larger system that has its own ubiquitous language and domain model. Bounding contexts gives team members a clear and shared understanding of what has to be consistent and what can be developed independently.

C

  • Client - A program element that is calling the element under design, using its capabilities.
  • Cohesion - Logical agreement and dependence.
  • Command - An operation that causes some change to the system (for example, setting a variable).
  • Context - The setting in which a word or statement appears that determines its meaning.
  • Context Map - A representation of the Bounded Contexts involved in a project and the actual relationships between them and their models.
  • Core Domain - The distinctive part of the model, central to the user’s goals, that differentiates the application and makes it valuable.

D

  • Data Transfer Object - A Data Transfer Object (DTO) is a data container which is used to transport data between layers and tiers. It mainly contains of attributes. DTOs are anemic in general and do not contain any business logic.
  • DDD - See Domain Driven Design.
  • Declarative Design - A form of programming in which a precise description of properties actually controls the software.
  • Domain Driven Design - Domain Driven Design is not a technology or a methodology. DDD provides a structure of practices and terminology for making design decissions that focus and accelerate software projects dealing with complicated domains.
  • Domain Layer - Contains the state and behavior of the domain.
  • Domain Service - Encapsulates business logic that doesn’t naturally fit within a domain object, and are NOT typical CRUD operations, those would belong to a Repository.
  • DTO - See Data Transfer Object.

E

  • Entities - Entities are characterized by having an identity that’s not tied to their attribute values. All attributes in an entity can change and it’s still the same entity. Conversely, two entities might be equivalent in all their attributes, but will still be distinct.
  • Event - An event represents something that took place in the domain. Since an event represents something in the past, it can be considered as a fact and used to take decisions in other parts of the system.

I

  • Infrastructural Layer - Supports all other layers, includes implementation of repositories, adapters, frameworks, etc.
  • Infrastructure Services - Used to abstract technical concerns (e.g. MSMQ, email provider, etc)

M

  • Model - A useful approximation to the problem at hand.
  • Modifier - See Command.

R

  • ** Root entity** - See aggregate root.

S

  • Saga - In essence, sagas listen for events and dispatch commands. A saga spans more than one messages and manages a process.

U

  • Ubiquitous Language - A language structured around the domain model and used by all team members to connect all activities of the team with the software. The idea is to avoid translations because they blunt communication and makes knowledge crunching anemic.
  • User Interface Layer - Accepts user commands and presents information back to the user.

V

  • Value Object - Value objects have no seperate identity; they are defined solely by their attribute values. Though we are typically talking of objects when referring to value types, native types are actually a good example of value types. It is common to make value types immutable.