In this post I present a methodology for implementing Domain-Driven Design (DDD) using F# and EventStore. The described approach makes use of idiomatic functional constructs, especially where they bring value beyond the traditional object-oriented and procedural paradigms. In this manner, the functional and object-oriented paradigms are contrasted. The natural alignment between functional programming and event sourcing is exploited and implemented with EventStore. Note that this project is a spike and is a work in early stages of progress.

In this post I compare and contrast the use discriminated unions and pattern matching in F# to the object-oriented paradigm, particularly in C#. Additionally, aspects of the object-oriented approach are linked with GoF design patterns, multiple dispatch and the open-closed principle. Ultimately, discriminated unions are shown to address deficiencies in the imperative, object-oriented approach.

Json.NET is a popular JSON serialization library on the .NET Framework. F# contains several types that aren’t supported by Json.NET out of the box because they don’t have direct analogs in C#. To enable support for these types in Json.NET a type provider implementation must be provided for each type. The types addressed in this post are option, list and tuple.

In this post I survey the evolution of various programming paradigms and emphasize the importance of expressing and isolating domain knowledge. Paradigms such as OOP, AOP, DCI, DDD, and Hexagonal are regarded as having a central goal of facilitating the representation of knowledge all while supporting integration with technical components. Finally I introduce a knowledge-driven architecture by Jeff Zhuk.

The notions of abstraction and encapsulation are prevalent throughout the realm of programming and are intimately related. Their differences are subtle indeed and warrant careful examination. Specifically, the differences are most apparent on the basis of intent. Ultimately, encapsulation can be viewed as a structural aspect of abstraction which can be employed without the intent to abstract.