Big Ball of Mud

A Big Ball of Mud is a haphazardly structured, sprawling, sloppy, duct-tape-and-baling-wire, spaghetti-code jungle. These systems show unmistakable signs of unregulated growth and repeated, expedient repair. Information is shared promiscuously among distant elements of the system, often to the point where nearly all the important information becomes global or duplicated. The overall structure of the system may never have been well defined.

Unfortunately, this architecture anti-pattern occurs quite commonly in the real world. Few designers intend to create one, but many projects inadvertently manage to create a mess because of lack of governance around code quality and structure.

For example, Neal worked with a client project whose structure appears here:

The client (whose name is withheld for obvious reasons) created a Java-based web application as quickly as possible over several years. The technical visualization shows their architectural coupling: each dot on the perimeter of the circle represents a class, and each line represents connections between the classes, where bolder lines indicate stronger connections. In this code base, any change to a class makes it difficult to predict rippling side effects to other classes, making change a terrifying affair.