This software component is a small Java module used to analyze a set of dependencies between things and determine "layers" of the dependency. Basically, the dependency tree can be imagined as a directed graph.
Layers work like this:
- Items that depend on no other things can be imagined as layer 0.
- Items that depend on only items from layer 0 make up layer 1.
- Items that depend on things from layer 1 (plus, possibly, items from layer 0) make up layer 2.
- And so forth...
In an ideal world, layers a non-cyclic, but many networks of dependencies fail to be non-cyclic. This code can still layerize cyclic graphs using a mathematical algorithm called the Greedy Cycle-Removal Algorithm.
This code has been open-sourced since 2008, but hasn't really been in a place that's easy to find.
Originally, this code was written to help analyze Java package dependencies. It was inspired by Edwin Hautus' paper on static package analysis (and the PASTA tool). I was a big fan of PASTA's approach to package visualization, but felt that the tool was limited in the way it handled subpackages. This dependency code was written as a first piece of an alternative package dependency analysis tool.
Subsequently, this code was used in other domains, including the processing of HL7 assets (including, for example, analyzing dependencies between HL7 MIF files and graphing the relationships between different HL7 message parts).