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Event Storming is a collaborative workshop-based technique used in software development and domain-driven design to quickly explore and model complex business processes. Introduced by Alberto Brandolini in 2013, Event Storming aims to bring together stakeholders from different backgrounds to create a shared understanding of a domain through the identification and mapping of domain events.

The primary purpose of Event Storming is to facilitate rapid learning and knowledge sharing about the business domain. By focusing on domain events—significant occurrences within the domain—participants can uncover the underlying processes, identify bottlenecks, and discover opportunities for improvement. This method helps bridge the gap between business experts and developers, ensuring that the software design aligns closely with business needs.

Event Storming revolves around several core concepts, including domain events, commands, aggregates, and policies. Domain events are noteworthy occurrences within the domain that have business relevance. Commands represent actions that trigger domain events. Aggregates are clusters of domain objects that are treated as a single unit. Policies are business rules or workflows that govern the interactions between events and commands.

There are different types of Event Storming workshops, each tailored to specific objectives and levels of detail. **Big Picture Event Storming** is used to explore the overall domain and identify major processes and events. **Process Level Event Storming** focuses on detailing specific business processes, mapping out events, commands, and aggregates in finer detail. **Design Level Event Storming** delves deeper into the technical aspects, including the design of aggregates, command handlers, and event handlers.

Setting up an Event Storming workshop involves gathering the right participants, preparing materials, and creating a conducive environment for collaboration. Participants typically include domain experts, developers, product owners, and other stakeholders. Materials such as sticky notes, markers, and a large wall or whiteboard are essential for visualizing the events and interactions. The workshop space should encourage open communication and active participation.

An Event Storming session typically begins with identifying and mapping domain events. Participants use sticky notes to write down events and place them on the wall or whiteboard in chronological order. Once the events are mapped, the group identifies commands that trigger these events and aggregates that encapsulate related events and commands. Policies and other relevant elements are added to complete the process map.

Identifying domain events is the first step in an Event Storming workshop. Domain events are significant actions or occurrences that have business relevance and impact. Participants brainstorm and write down these events on sticky notes, which are then placed on the wall in the order they occur. This step helps create a timeline of events and provides a foundation for further exploration.

After identifying domain events, the next step is to map the commands that trigger these events and the aggregates that manage them. Commands represent user actions or system triggers that initiate events. Aggregates are clusters of related entities and value objects that ensure consistency and encapsulate business rules. This step helps define the interactions between different parts of the domain.

Policies, which are business rules or workflows, are added to the map to show how events and commands are governed. External systems that interact with the domain, such as third-party services or external databases, are also identified and included in the map. This comprehensive view helps participants understand the complete landscape of the domain and its dependencies.

Event Storming is highly collaborative, encouraging active participation and discussion among all attendees. As events, commands, and aggregates are mapped, participants ask questions, challenge assumptions, and provide insights based on their expertise. This collaborative exploration helps uncover hidden details, resolve ambiguities, and ensure a shared understanding of the domain.

Event Storming offers several benefits, including rapid discovery of domain knowledge, improved communication among stakeholders, and enhanced alignment between business needs and software design. By involving all relevant parties in the modeling process, Event Storming ensures that the resulting model accurately reflects the domain and addresses real business challenges.

Despite its advantages, Event Storming can present challenges such as ensuring active participation from all attendees, managing the complexity of large domains, and facilitating productive discussions. Overcoming these challenges requires effective facilitation, clear communication, and a focus on achieving the workshop's objectives.

The facilitator plays a crucial role in the success of an Event Storming workshop. The facilitator guides the process, encourages participation, manages time, and helps resolve conflicts. An effective facilitator ensures that the workshop stays on track, that all voices are heard, and that the outcomes are valuable and actionable.

Event Storming is an iterative process, with multiple sessions often needed to refine the domain model. Initial workshops may focus on broad exploration, while subsequent sessions delve deeper into specific processes or technical details. This iterative refinement helps ensure that the model evolves based on new insights and feedback, resulting in a robust and accurate representation of the domain.

Event Storming is closely aligned with Domain-Driven Design (DDD), providing a practical technique for discovering and modeling domain concepts. The insights gained from Event Storming can inform the creation of bounded contexts, aggregates, entities, and value objects within the DDD framework. This integration enhances the overall effectiveness of the design process.

Event Storming has been successfully applied in various industries, including finance, healthcare, e-commerce, and manufacturing. Organizations use Event Storming to model complex domains, redesign business processes, and develop new software systems. Real-world case studies demonstrate the method's versatility and effectiveness in addressing diverse business challenges.

While traditional Event Storming relies on physical materials like sticky notes and whiteboards, digital tools are also available to facilitate remote or hybrid workshops. Tools such as Miro, MURAL, and Lucidchart provide virtual canvases for mapping events and collaborating in real-time. These tools help teams conduct Event Storming sessions regardless of their physical location.

To maximize the benefits of Event Storming, teams should follow best practices such as preparing thoroughly, ensuring diverse participation, focusing on domain events, and maintaining an open and collaborative atmosphere. Regularly reviewing and updating the event map based on new insights and feedback helps keep the model relevant and accurate.

Event Storming is a powerful and flexible technique for rapidly exploring and modeling complex business domains. By fostering collaboration and leveraging visual modeling, Event Storming helps teams uncover domain knowledge, improve communication, and align software design with business needs. Its integration with Domain-Driven Design (DDD) and applicability across various industries make it a valuable tool for modern software development.

• Event Storming official site: https://www.eventstorming.com/
• Alberto Brandolini's book “Introducing EventStorming”: https://leanpub.com/introducing_eventstorming
• Domain-Driven Design (DDD) Community: https://dddcommunity.org/
• Digital collaboration tools: https://miro.com/, https://www.mural.co/, https://www.lucidchart.com/
• Overview of Event Storming: https://martinfowler.com/articles/2014-event-storming.html