Visualise coupling between contexts in Big Picture EventStorming

A Big Picture EventStorming is a type of EventStorming where you get business and IT from an organisation into one room to explore the entire line of that business. This way we can find competing goals, ambiguity in the language, communication boundaries between contexts, and most important we share knowledge! We end up with a visual overview of our business architecture and can map our IT systems on or do for instance a value stream mapping. But we can also map and visualise coupling between contexts in Big Picture EventStorming. In this blog post, I will share my insights on how I visualise contexts boundaries in a Big Picture EventStorming.

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EventStorming the perfect wedding

Arranging a wedding is an exciting time to look forward to, but also comes with a lot of stress, especially when planning for it. For most of us, it will be the first time to plan our wedding, and, at least for me, hopefully, also the last. We can, of course, always hire a party planner (sort of like the domain expert on weddings), but getting married is already expensive enough, and for most of us this is not an option. Besides, there is also the family wishes to take in consideration, and might it just be that sometimes our family can also be domain experts. Let’s face it, they already seen there fair share of weddings, and most of them already have experience getting married themselves. We should consider their wishes and especially take advantage of their knowledge. Well, we can, with EventStorming! (and yes, I am the bridezilla of the two).

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Crossing the bounded context, events-first, the REST is not needed

Technical design decision can have a severe impact on companies their communication structure. Conway’s law explains; “Any organization that designs a system (defined more broadly here than just information systems) will inevitably produce a design whose structure is a copy of the organization’s communication structure.” Such is the story also with a microservices architecture. A lot of companies decide to use REST to communicate between bounded contexts and or services. What can happens is that the services in the bounded context now get dependent on each other. The dependency on finishing a service their process will resolve in cascading failures if a service is down. Cascading failures will reflect on the way organizations communicate between teams. Teams now rely on each other before finishing their process. Dependency between teams can severely disrupt the company to respond better to the fast-changing demands of customers; companies get more entangled than before. To combat getting cascading failures, we must follow the communication structure of the business. We can do this by using Event Storming and going events-first.

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Combining Domain Driven Design and Behaviour Driven Development

In my previous post, I discussed why we want to write software with empathy in mind; software that is understandable for peers. For us to create software with empathy in mind, we need to create a shared understanding of the users’ needs; the needs we are trying to satisfy with our software. Practices like Domain Driven Design (DDD) and Behaviour Driven Development (BDD) can help us achieve this. By using Feature Mapping (a technique from BDD) and improving this with Event Storming (a technique from DDD), we can create executable specifications and a model for our business needs at the same time. This way, we can write software and tests that match the shared understanding the business has, which enables us to ship more value faster.

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