Marcus Ilgner

Domain-Driven Development and GenAI

Sun, 21 Sep 2025 12:44:00 +0200

Increased utility of Domain-Driven Development in the context of GenAI Link to heading

These days it sometimes seems like “AI” is the only topic being thrown around in software development circles. Personally I’m mostly ambivalent on the topic but tend to rarely use it: a big - if not the most important - part of software development is asking questions, which is something that LLMs are notoriously bad at. That’s largely because their modus operandi and tuning is aimed to produce good-sounding answers instead of questions. So it tends to funnel output into specific directions - something which can easily be exacerbated through imprudent prompts or subliminal tendencies in their training data.

Hibernate Initialisation without XML

Tue, 21 Feb 2023 17:16:00 +0200

Hibernate Initialisation without XML Link to heading

While working on some R&D last weekend, I was surprised when every introduction to Hibernate started with creating a persistence.xml file.

Ultimately this is probably because many developers implicitly assume that ones JPA persistence unit will ultimately be managed by an application server. But for small containerised applications without application server, having multiple mechanisms to configure the application - i.e. persistence.xml and whatever native mechanism one prefers - is extremely unwieldy. As an example, I have seen some really convoluted approaches for referencing environment variables to pull in database credentials.

5 things I learned from 18 months with OPC UA

Sun, 04 Dec 2022 13:32:00 +0200

5 Things I learned from 18 months with OPC UA Link to heading

Although it feels like a much longer time, it was in May 2021 that I joined the team at RE:. Now, 18 months later, it feels like a good time for a recap. I’ll start with one of the most prominent topics that I encountered: OPC UA. This job is my first within the context of mechanical engineering and while I have worked with many different technologies and built a large variety of systems over the past two decades, this was a novel experience (and also part of the reasons why I decided to join). Overall it is probably fair to say that software development in this industry works differently from “regular”, or “digital-only” software.

The Importance of Clean Code for Agile Teams

Thu, 07 Jul 2022 19:56:00 +0200

The Importance of Clean Code for Agile Teams Link to heading

Most everyone who works in software development will know the situation where you have written some code that manages to somehow solve a current problem - but when looking at it the next day (or showing it to another person), it turns out that there are a couple of design issues with it.

Now the question automatically arises: should we merge it or give it a bit of love and clean it up?

Becoming a better developer

Thu, 09 Jun 2022 22:05:00 +0200

Programming isn’t software development Link to heading

While it might be obvious to many or most people, it nonetheless needs to be said sometimes. But before getting to the interesting part about how to move from programming to software development and how to become better at that, let’s start with an example of what I’m talking about. To illustrate the underlying concept, let’s use a completely ludicrous, over-the-top example 🤪

Let's talk about Pet Projects

Wed, 18 May 2022 21:00:00 +0200

Let’s talk about pet projects Link to heading

In many years reviewing job applications from software developers, one topic has come up as surprisingly controversial time and again: pet projects, i.e. projects that developers work on on their own time. So let’s have a look and see what the fuzz is all about.

From the employers perspective Link to heading

First, let’s look at it from the employers perspective. A colleague of mine once succinctly put it like this: “You wouldn’t expect a slater to tile a roof in their free time, would you?”. And there’s a lot of truth to that.

Rails Value Objects

Wed, 04 May 2022 01:06:00 +0200

Value Objects in Rails Link to heading

While writing yesterdays post about the usage of Hash vs class, I couldn’t help but think of another powerful tool that helps us to build a well-defined model of our problem domain in the programming language of our choice: the value object.

To understand the value of value objects (scnr), let’s take an example: 42. “What is 42?”, you might be tempted to ask - and rightfully so. In Ruby it might be an instance of Integer, other languages may have cause to use a more restrictive definition like u8 or i16. But still - that doesn’t help us to understand what 42 might mean.

Idiomatic Coding: Ruby Hash (& Python Dict)

Tue, 03 May 2022 08:48:10 +0200

Idiomatic Ruby: `Hash` vs `class` Link to heading

It is no secret that I’m a big fan of typed languages. To me, an expressive type system really helps to convey the mental model of the application to the developers maintaining the code base.

As such, I am often dismayed when reading code from untyped interpreted languages. Sure, there are classes in Javascript, Ruby and Python. But very often I find that they’re eschewed in favour of just bundling a list of attributes together in an untyped Object, Hash or Dict respectively.

Projects

Tue, 03 May 2022 08:45:35 +0200

Here’s a short excerpt from my past and current (public) projects:

SR6 Character Sheet: when our gaming group switched to online play during the COVID-19 pandemic, I built a digital character sheet for Shadowrun 6
Keedrop: easily & securely send passwords. It doesn’t replace GPG, but at least you won’t have to send them in plaintext over chat or email.
k290-fnkeyctl: when I got myself annoyed with the way that my Logitech keyboard handled its function keys, I reverse-engineered a small application to switch the behaviour on Linux.
SQLite3-WinRT, metro-driver and Win8-Cucumber.js: working at doo (nowadays called Scanbot), we pioneered development on the then new Windows 8 platform and wrote a SQLite3 adapter as well as tooling for automated testing of our application.
Compoker is a small complexity poker app which was my first project written in Rust. It was only meant to teach me a bit of Rust and learn some Svelte along the way. It’s probably going to remain a bit of a Rust learning playground for me.
ActiveActivity is my most recent project. When working in a Rails project at work, I noticed that there’s no built-in facility to orchestrate continuously-running activities in Rails - so I built it. Still in alpha stage.

Wikis aren't meant for software documentation

Thu, 20 May 2021 20:39:10 +0200

Wikis aren’t meant for software documentation Link to heading

“Documentation is a love letter that you write to your future self.” – Damian Conway

Although there are many arguments being made to rationalize our laziness and avoid writing proper documentation, there is no doubt in my mind that good software documentation is a great tool to improve the development lifecycle of long-running projects.

If you know your project is going to be scrapped in 2 months time, feel free to stop reading here and enjoy a good book or a walk outside. ☀️ But if it’s any more than that, you should make your live and the lives of your co-workers easier by documenting your software. Even projects with a originally limited lifetime have been known to live long past their best- before date.

Imprint

Mon, 05 Apr 2021 14:45:59 +0200

Impressum Link to heading

Angaben gemäß § 5 TMG; verantwortlich für den Inhalt nach § 55 Abs. 2 RStV:

Marcus Ilgner
Kölner Str. 98
53840 Troisdorf
Deutschland

Kontakt Link to heading

Fax: 02241 1695662
E-Mail: [email protected]" >[email protected]

Haftungsausschluss: Link to heading

Haftung für Links Link to heading

Dieses Angebot enthält Links zu externen Webseiten Dritter, auf deren Inhalte ich keinen Einfluss habe. Deshalb kann ich für diese fremden Inhalte auch keine Gewähr übernehmen. Für die Inhalte der verlinkten Seiten ist stets der jeweilige Anbieter oder Betreiber der Seiten verantwortlich. Die verlinkten Seiten wurden zum Zeitpunkt der Verlinkung auf mögliche Rechtsverstöße überprüft. Rechtswidrige Inhalte waren zum Zeitpunkt der Verlinkung nicht erkennbar. Eine permanente inhaltliche Kontrolle der verlinkten Seiten ist jedoch ohne konkrete Anhaltspunkte einer Rechtsverletzung nicht zumutbar. Bei Bekanntwerden von Rechtsverletzungen werde ich derartige Links umgehend entfernen.

Deploy a Vert.x app with an embedded SPA

Mon, 05 Apr 2021 13:31:04 +0200

Deploy a Vert.x application with an embedded SPA Link to heading

As a developer I have come to enjoy the versatility and power of the Vert.x platform. And although it contains many utilities for server-side rendering, called Vert.x Web, there are situations where you might want to use a single-page application (SPA) instead.

Concrete reasons for and against SPAs are best kept separate from this. One thing, however, that makes SPAs cumbersome for small teams is having to deploy them separately from the API they will talk to, so having a setup that allows for deploying everything in one go.

About me

Sat, 26 Oct 2019 16:19:45 +0200

Born 1982, I spent my teenage years witnessing and exploring the rise of the internet. Since, I have been able to gather professional experience in a number of technologies: everything from network security and setting up Sendmail-based mail servers 📨, doing computer games development in C++ and DirectX 🎮, via Java business software 💼 up to web applications with Ruby On Rails 💎 and real-time data processing applications with Vert.x ✈️.