Mathias Verraes

Splitting a Domain Across Multiple Bounded Contexts
Article How designing for business opportunities and the rate of change may give you better contexts.

The “It's Just Like...” Heuristic
Article Why feeling that you understand a new idea, is a sign that you didn't.

Simple Models, Scaffolding, Enabling Constraints
Article Simple models are more wrong than complex ones, but they can be useful to detect problems, and to kickstart more suitable models.

Tensions when Designing Evolvable Bounded Contexts
Article Bounded Contexts and their interfaces are governed by fundamental tensions that affect our design

The Legacy Mirror Heuristic
Article Evaluate a novel idea by swapping the old and the new idea in time.

The Wall of Technical Debt
Article A method for making technical debt visible and negotiable.

Eventsourcing: State from Events or Events as State?
Article Comparison of two common interpretations of eventsourcing; and proposing a definition.

Patterns Are Not Defined by Their Implementation
Article Design Patterns express a problem in a context with a reusable solution.

Temporal Modelling
Presentation How reasoning with time helps you model software better than structure.

Emergent Contexts through Refinement
Article Refine a model and its language until opportunities for better Bounded Contexts emerge.

Messaging Patterns: Natural Language Message Names
Article Embed more meaning in messages by using verbs.

Eventsourcing Patterns: Migration Events in a Ghost Context
Article Explicitly conform to the legacy component's model in an eventsourcing migration.

Eventsourcing Patterns: Decision Tracking
Article Store the outcome of a decision to guard against rule changes.

Messaging Patterns: Throttling
Article Only keep one event per time unit from a high frequency stream.

Messaging Patterns: Ephemeral Events
Article An event's lifetime lasts until the next event.

Messaging Patterns: Change Detection Events
Article Listen to a stream of events and produce a new event when a value changes.

DDD and Messaging Architectures
Article An overview of my different series on patterns in distributed systems.

Eventsourcing Patterns: Crypto-Shredding
Article Encrypt sensitive information in an event and delete the key.

Eventsourcing Patterns: Forgettable Payloads
Article Store the sensitive payload of an event in a separate store to control access and removal.

Patterns for Decoupling in Distributed Systems: Segregated Event Layers
Article Explicitly segregate a Bounded Context's events in visibility layers, with their own language.

Patterns for Decoupling in Distributed Systems: Fat Event
Article Add redundant information to a Domain Event to reduce complexity in the consumer.

Patterns for Decoupling in Distributed Systems: Explicit Public Events
Article Mark a small subset of events as public, keep the rest private by default.

Patterns for Decoupling in Distributed Systems: Passage of Time Event
Article Replace cron jobs and scheduled commands, with an agnostic event to indicate the passage of time.

Patterns for Decoupling in Distributed Systems: Summary Event
Article Instead of emitting a stream of Domain Events, emit a single Summary.

Patterns for Decoupling in Distributed Systems: Domain Query
Article Replace Free Queries with Domain Queries to decouple from knowledge of the server's internals.

Patterns for Decoupling in Distributed Systems: Completeness Guarantee
Article Design the set of Domain Events from a producer so that they can be used to rebuild the producer's state.

Design Heuristics
Presentation Distilling your design heuristics using practical examples.

Emergent Boundaries
Presentation

Messages Over Structure
Presentation

On Being Explicit
Presentation Software design stories

Designed Stickiness
Presentation How sticky metaphors can communicate better software models.

Lightning Talks
Presentation Five minute lightning talks, to practice public speaking.

The Repair/Replace Heuristic for Legacy Software
Article How understanding the history of systems aids strategic decisions

Property-based testing
Presentation

Code Reviews and Blame Culture
Article A common belief is that gated reviews lead to blaming individuals. The opposite can be true.

Type Safety and Money
Article All good design is redesign.

Domain-Driven Design workshops
Article

Towards Modelling Processes
Presentation A temporal view of business problems leads to deeper models.

Context Mapping: Life Expectancy
Article When Context Mapping a complex environment, indicate the Life Expectancy of each Bounded Context, as well as its sponsors and other relevant metadata.

Event Storming, Storytelling, Visualisations
Article About telling non-linear stories with stickies, and visualising complications in Event Stormed models.

Form, Command, and Model Validation
Article Make a clear distinction between different layers of validation.

Messaging Flavours
Article Differentiating between informational, interrogatory, and imperative messages, and keeping them nicely separated.

Economy of Tests
Article Migrate test levels to improve the long term sustainability of your test suite.

How Much Testing is Too Much?
Article Run an experiment to learn how much unit tests you actually need.

Let It Crash
Article The Erlang view of the world is that everything is a process and that processes can interact only by exchanging messages.

Higher Order Programming
Article map(divide(__, 2), __) and other excursions into elegant functional programming in PHP

Modelling Heuristics
Presentation Mental tools to help you discover model variations

Domain Events
Article Domain Events allow you to segregate the models of different systems

Object Reorientation
Presentation Introductory talk to programming with objects

“Software design is just theory”
Article Is writing code all day all you need to do to become a better programmer?

Small Uncontrolled Experiments (revisited)
Presentation How to improve when you don't know how to improve

Objects as Contracts for Behaviour
Article Even in the real world, the potential behaviours of an object are essential to that object.

Decoupling the Model from the Framework
Presentation Presentation on Domain-Driven Design, CRUD, Task-based UI's, Commands, Events, ...

Sterile Estimation
Article The Anchoring Bias, well-known to psychologists, prevents you from making quality estimates.

Resolving Feature Envy in the Domain
Article Expressing the Ubiquitous Language helps us to get rid of the Feature Envy code smell.

DRY is about Knowledge
Article Code duplication is not the issue.

Event Storming: on Fake Domains and Happy Paths
Article More Event Storming insights: picking good domains, modelling branches using duplication, and creative visualisation.

Managed Technical Debt (revisited)
Presentation Are you sweeping technical debt under the rug?

Information Overload
Article Learn by finding the differences, not the similarities.

The Cost of Estimation
Article Asking for estimates can cost you more than you think. When you do estimate, take into account time, complexity, and risk.

When to Use Static Methods
Article Static methods? Yes, when they are stateless.

Named Constructors in PHP
Article Don't limit yourself by PHP's single constructor. Use static factory methods.

Why Domain-Driven Design Matters
Presentation Thinking about Systems and Complexity.

A Functional Foundation for CQRS/ES
Article A CQRS architecture can be seen as a set of referentially transparent functions that model decisions and interpretation.

Final Classes: Open for Extension, Closed for Inheritance
Article Composition, strategies, callbacks, plugins, event listeners, ... are all valid ways to extend without inheritance.

Small Uncontrolled Experiments
Article How we made continuous improvement truly continuous, using stickies, a timeline, and few minutes each day.

Practical Event Sourcing
Presentation A step by step guide to building your very first Event Sourced Aggregate.

Religiously RESTful
Article REST: The language of the future, or opium for the masses?

Buzzword-free Bounded Contexts
Article My recent attempt at explaining Bounded Contexts at @DDDBE, was criticised for being too heavy on terminology. Rinse, adjust, repeat.

Domain-Driven Design: Bounded Contexts, Modelling
Presentation Gentle introductions to DDD by the founders of DDD Belgium.

Model Storming Workshop
Presentation Deliberately discover your domain, to get in Modelling Nirvana.

Bandwidth and Context Mapping
Article Context Mapping is about the whitespace between systems, and the bandwidth of the communications.

Build for Failure
Article Admit failure. Build for failure. Live failure.

The Henry Ford Fallacy
Article

Domain-Driven Design is Linguistic
Article Just because two behaviours lead to the same outcome, does not mean they are replaceable.

Related Entities vs Child Entities
Article Making the difference between Related Entities and Child Entities explicit, and choosing your modelling strategy accordingly, will pay off in the long term.

Fighting Bottlenecks with CQRS
Presentation CQRS challenges the assumption that reading and writing are supposed to share the same abstractions.

Value Objects and User Interfaces
Article Separate value objects in your model from concepts that serve the UI.

Pre-merge Code Reviews
Article Rules, benefits, patterns, and anti-patterns for reviewing code before merging it.

Verbs in Class Names
Article Use a verb to build a sentence. There will be no translation to code in your brain. The sentence _is_ the code.

Sensible Interfaces
Article How did we get from 'Program to an interface, not to an implementation' to 'Just slap an interface on there, it's the fashionable thing to do'?

Extract Till You Drop
Presentation If I'm not afraid to refactor messy code in front of a live audience, you shouldn't be afraid to do it in the comfort of your office.

The DDDBE Modellathon
Presentation

Antifragile - Things That Gain from Disorder
Article Robustness only goes so far. Embrace a system's natural antifragility.

Facilitating Event Storming
Article Domain-Driven Design modelling for Agile teams, Brandolini-style.

Switch - How to Change Things When Change Is Hard
Article Switch is a framework for change that aims to operate on the emotional side, the logical side, and the environment.

Systemantics - The Systems Bible
Article The System Kicks Back, Gets In The Way and Opposes Its Own Proper Function. Your own perspective becomes distorted by being In The System.

Managed Technical Debt
Article We should make a distinction between Managed and Unmanaged Technical Debt.

Unbreakable Domain Models
Presentation

Decoupling (Symfony2) Forms from Entities
Article Avoid tight coupling between your forms and your Entities by using the Command pattern as an intermediate.

CRUD is an antipattern
Article CRUD doesn't express behaviour. Avoid setters, and use expressive, encapsulated operations instead.

Casting Value Objects to strings
Article Cast Value Objects to strings that can be parsed back into the Value Object.

Using Contextual Code Formatting for Readability
Article Format code to draw attention to what's important.

How to read more books
Article An ever-growing list of tips that help me read more books.

Javascript Dependency Injection with partial functions
Article

Code Folder Structure
Article

Coping with Change in Software Development
Article Change is not your enemy, it's your job.

Lazy Loading in PHP with Closures
Article

Ubiquitous Language
Article

Beautiful code
Article

Representing Money in PHP, Fowler-style
Article

Random thoughts on using Git
Article

Accessing private properties from other instances
Article

Keep your controllers thin with Doctrine2
Article

Interface discovery with PHPUnit’s Mock objects
Article