Over recent years, a tool called EventStorming became one of the go-to techniques for Domain-Driven Design consultants to collaboratively explore complex business domains at customers. Since consultants travel a lot from company to company helping with their questions about approaching software delivery this poses a small 1st world problem; How can we still comfortably travel while still carrying the required equipment to do an EventStorming at the customer (without breaking our back or needing a personal fitness coach). This was exactly the conversation we, Maxime Sanglan-Charlier and Kenny Baas-Schwegler, had during DDD Europe 2019. In this post, Maxime and Kenny will share their quest in finding the perfect EventStorming backpack.(more…)
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.(more…)
While Bruno Boucard, Thomas Pierrain, and I were preparing our DDDEurope 2019 workshop, we discussed how to approach Example Mapping. For the workshop, we were combining EventStorming and Example Mapping to go from problem space to solution space. The way I have been approaching Example Mapping was slightly different then Thomas and Bruno did. Mine followed up more on EventStorming, standing in front of a wall storming examples first with stickies. Bruno and Thomas do it the way that was described byMatt Wynne from cucumber, standing in a group around a table, starting with a user story and one rule written on index cards. So we began to discuss in short what these difference are, and what the trade-off was when we did these. In this post, I will explain the different heuristics on approaching Example Mapping in this post.(more…)
with EventStorming and Example Mapping
This article was published in the leanpub book: Domain-Driven Design: The First 15 Years
People often ask for more concrete guidance on how to explore models, especially in an Agile or Lean setting. The model exploration whirlpool is Eric Evans attempt to capture such advice in writing. It is not a development process, but a process that fits in most development processes. The central theme revolving the process is to keep challenging the model. While the process itself for most is straightforward and easy to understand, there are not many concrete examples to find on how to do such a model exploration whirlpool. Most people when starting to use Domain-driven design (DDD) are looking for these practical examples. In this article, I will tell you my story of how I used the model exploration whirlpool by combining EventStorming, a technique that came from the DDD community, and Example Mapping, a technique from Behaviour Driven Development (BDD) community.(more…)
Moving towards a microservices architecture
We see a lot of companies are moving towards a microservice architecture. The big pitfall of microservices architecture is to focus on the technology, how big the microservice needs to be, how many lines of codes, what entities do we put in a microservice, and using rest as the communication between them. But to succeed we need to focus on the problem space, by crunching domain knowledge and do domain modelling. EventStorming is a perfect fit for domain modelling, and almost all the microservices leaders seem to agree. Even ThoughtWorks finally put EventStorming on ‘adopt’ in their most recent rendition of their technology radar. But EventStorming has grown to be more than just a tool for domain modelling and to be successful and create autonomous teams you need to use EventStorming for more than only domain modelling.
We design, model, and create software to solve a problem for our customer (this can also be a customer from within the same company). Only when we do so, we focus naturally on solving the happy path and want to deliver that value as soon as possible. The only problem here is that we will always come to a point where we get corner cases or business exceptions, and the question starts to arise, what shall we do? Is it worth the effort to invest in building a solution for this, or can we leave this function out of the system because it is not worth it? To answer this question, we want, if possible, feedback from the system to know this. We can quickly get this feedback making it explicit in the form of a Domain Event during our EventStorming and start monitoring it. This way we can leave the options open until we know what to do.
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).
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.
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.
One of the biggest challenges as engineers is to write working software and also keep an extensive documentation. Most engineers hate writing documentation, and after they published documentation on a wiki it will die a lonely death. We want to strive for writing a Living Documentation in an Ubiquitous Language. Practices like Domain Driven Design (DDD) and Behaviour Driven Development (BDD) can help you achieve this. Especially when we start writing code, it is really important for the quality of our software to start with tests describing what your application does. We want to write software with empathy in mind, software that is understandable for peers. While software developers are beginning to use the language of the domain (business language) more in their application code, most tests still contain a lot of technical language.