Anticorruption Layer

The anticorruption layer relationship refers to a design pattern in which an intermediate layer is created between two bounded contexts to facilitate communication between them. The anticorruption layer acts as a bridge between two different domains and ensures that each bounded context can maintain its own language and terminology without being affected by the other.

The anticorruption layer provides a translation layer that maps the data between the two contexts, and enforces the boundaries between them. It acts as a filter to ensure that the corrupting influence of one context does not affect the other. This relationship is useful when there is a need to integrate with legacy systems or external systems that use different terminologies, technologies or data structures.

The goal of the anticorruption layer relationship is to protect the integrity and autonomy of each bounded context while still allowing them to work together effectively.

Implications

The anti-corruption layer relationship between bounded contexts has the following pros and cons:

Pros

  • Allows for the integration of legacy systems with modern systems using a translation layer, without affecting the domain model of the new system.
  • Helps to ensure that domain model integrity is preserved in the new system by isolating any legacy systems that may not conform to the new system’s domain model.
  • Encourages the development of a clean separation of concerns between the new and legacy systems.

Cons

  • Requires additional development effort to build and maintain the anticorruption layer.
  • Can add complexity to the overall system architecture.
  • Can introduce additional points of failure in the system if the anticorruption layer is not implemented correctly.

Overall, the use of an anticorruption layer can be a valuable tool for integrating legacy systems with modern systems in a way that preserves domain model integrity and encourages separation of concerns, but it does require careful consideration of the additional development effort and potential complexity it may introduce.

Example

Let’s say we have two bounded contexts: a legacy system that handles customer information, and a new modern system that needs to use that customer information. The legacy system uses its own database schema and naming conventions that are incompatible with the modern system’s. We can introduce an anticorruption layer between the two contexts to translate the data from the legacy system into a format that the modern system can use.

The anticorruption layer would be responsible for:

  • Understanding the legacy system’s data model and how it differs from the modern system’s
  • Translating the data from the legacy system’s format into the modern system’s format
  • Exposing a clean and consistent interface to the modern system that shields it from the complexities of the legacy system

When does it work?

The anticorruption layer relationship is effective in the following scenarios:

  1. When multiple bounded contexts have their own domain models and languages and need to communicate with each other. In this case, the anticorruption layer acts as a bridge between the two contexts, translating the domain model and language of one context to the other.
  2. When a bounded context needs to interact with a legacy system that has a different domain model and language. In this case, the anticorruption layer can be used to translate the domain model and language of the legacy system to the bounded context’s domain model and language.
  3. When a bounded context needs to interact with an external system or API that has a different domain model and language. In this case, the anticorruption layer can be used to translate the domain model and language of the external system to the bounded context’s domain model and language.

Overall, the anticorruption layer relationship is effective when there is a need to decouple different bounded contexts or systems that have their own domain models and languages, and to prevent the contamination of a bounded context’s domain model by the domain model of another context or system.

When does it not work?

The anticorruption layer relationship between bounded contexts is a powerful tool for keeping bounded contexts independent, but it does come with some tradeoffs. One major tradeoff is the added complexity and overhead of implementing and maintaining the anticorruption layer. Additionally, if the anticorruption layer is not designed correctly or if it is not kept up-to-date with changes in the bounded contexts it is protecting, it can become a bottleneck or a source of bugs.

The anticorruption layer relationship works most effectively when there is a clear need for it and when it is designed and implemented correctly. It is particularly useful in cases where there are legacy systems or external systems with their own data models that need to be integrated with a new system built using DDD. In such cases, an anticorruption layer can be used to translate between the different data models and ensure that the new system is not contaminated by the old system’s design.