Four Strategies for Dealing with Legacy Systems

Posted on: 08-25-2011

Presentation by Eric Evans at the DDD-NYC meetup in August 2011, recorded and edited by Alex Hung.

We say that effectively applying the tactical techniques of domain-driven design (DDD) requires a clean, bounded context. This can be a daunting requirement when your work is dominated by legacy systems. These systems are often tangled, and even when they are orderly they are usually not suited to DDD. This presentation describes four strategies for getting started with DDD when you have a big commitment to legacy systems.

These strategies were also described in a white paper in 2013.

Note: The short video Modeling for a Purpose within Bounded Contexts, from the same meeting, gives a quick introduction to the concepts used in these strategies, in particular, “bounded context”.

Start watching » (Total running time: 1 hour)

Video in segments:

Part 1: Why legacy replacement is a bad strategy – and what’s the alternative? (12:42)

Part 2: Strategy 1, Bubble Context (7:23)

Part 3: Strategy 2, Autonomous Bubble (7:41)

Part 4: Strategy 3, Make Legacy Assets Accessible as Open Host Services in Published Language (11:08)

Part 5: Strategy 4, Event Streams, Conclusion (19:17)

Categories: Library, Strategic Design Tags: Eric Evans