In Domain-Driven Design (DDD), the partnership relationship is a type of relationship between bounded contexts. In this relationship, two or more bounded contexts collaborate in a way that they have a shared understanding of each other’s models and how they interoperate. The goal of this partnership is to provide a complete and comprehensive solution to the domain problem that the system is solving.

In a partnership relationship, the bounded contexts are not completely independent of each other, but they still maintain some level of autonomy and independence. The collaboration between them is based on a shared domain model, which is agreed upon by all the participants in the partnership. This model acts as a lingua franca that allows the different teams to communicate effectively and build solutions that work well together.

The partnership relationship is useful when the bounded contexts need to share data or collaborate to provide a complete solution to the domain problem. This relationship is typically established between bounded contexts that are closely related and have a significant impact on each other’s behavior.

Implications

Partnership relationships between bounded contexts can have both advantages and disadvantages:

Pros

• Partnership relationships can facilitate communication and collaboration between teams working on different bounded contexts.
• They can help to align the ubiquitous language and ensure that the various models are consistent and complementary.
• They can enable the creation of more cohesive, end-to-end solutions that span multiple bounded contexts.
• They can provide opportunities for cross-context reuse of services or components.

Cons

• Partnership relationships can create dependencies between teams and bounded contexts, which can make it more difficult to evolve the system as a whole.
• They can introduce additional communication and coordination overhead.
• They can make it more challenging to maintain the autonomy and independence of the bounded contexts.
• They can increase the complexity of the overall system and make it harder to reason about.

Example

Let’s say we have a bounded context for an e-commerce platform, which includes a Shopping Cart aggregate that handles all the logic related to adding items to the cart, updating quantities, and processing orders. Another bounded context in the system is a Payment Processing service that is responsible for handling payments.

In this scenario, we can establish a partnership relationship between the Shopping Cart and Payment Processing contexts. This means that when an order is submitted in the Shopping Cart context, the Payment Processing context is notified and can begin processing the payment. If the payment is successful, the Shopping Cart context is notified so it can complete the order, but if the payment fails, the Shopping Cart context can take compensating actions to cancel the order.

This partnership relationship allows the two bounded contexts to work together to accomplish a common goal, while still maintaining their own independent logic and data structures. The downside of this approach is that it can add complexity and dependencies between the contexts, so it should be used judiciously and only when necessary.

When does it work?

For a partnership relationship between bounded contexts to work effectively, the following conditions need to be true:

1. Shared domain language: Both bounded contexts should agree on the language and terminology used to describe domain concepts and activities.
2. Strong collaboration: Effective collaboration between the teams responsible for each bounded context is essential. There should be clear communication and frequent interaction to ensure alignment of goals and activities.
3. Clear boundaries: The boundaries of each bounded context should be well-defined to avoid overlap and confusion.
4. Explicit context map: The relationship between the bounded contexts should be explicitly documented, including the interactions between the teams responsible for each bounded context and the rules governing those interactions.
5. Consistency and stability: The interface between the bounded contexts should be stable and consistent over time to avoid disruptions to the relationship.
6. Mutual benefit: Both bounded contexts should derive mutual benefit from the partnership. This could include sharing of data or functionality, or more efficient delivery of business value.

When does it not work?

Partnership relationships may not work in the following scenarios:

1. Lack of trust: In a partnership relationship, each bounded context should trust the other to fulfill their responsibilities. If there is a lack of trust, it can lead to conflicts and misunderstandings.
2. Misaligned goals: If the goals of the bounded contexts are not aligned, it can lead to conflicts and disagreements. For example, if one bounded context is focused on optimizing for speed, while the other is focused on data consistency, there can be conflicts.
3. Communication issues: Partnership relationships require effective communication and collaboration between the teams. If there are communication issues or cultural differences between the teams, it can lead to misunderstandings and conflicts.
4. Unequal contributions: In a partnership relationship, both bounded contexts should contribute equally to the overall goal. If one bounded context is doing all the heavy lifting while the other is not contributing enough, it can lead to resentment and conflicts.
5. Changes in business requirements: If there are changes in business requirements, it can impact the partnership relationship. For example, if the goals or requirements of one bounded context change, it can impact the other bounded context as well. This can lead to conflicts and disagreements if the two bounded contexts are not able to adapt to the changes effectively.