IT:AD:Patterns:Reference Downward Only [Notes]

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# IT:AD:Patterns:Reference Downward Only #



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Software Circular Dependencies between modules are problematic due to the tight coupling of the mutually dependent modules which renders the separate re-use and testability of a single module impossible.

Circular Dependencies may also cause memory leaks by preventing certain very primitive automatic garbage collectors (those that use reference counting) from deallocating unused objects.


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## Recipe ##

After applying the recommendated [[IT/AD/Patterns/Minimal Dependency Cardinality/]] pattern -- to minimize circular dependencies -- the same guidelines apply to [[IT//AD/Development/Patterns/DDD/]] based applications as older architecture patterns: 

    Assembllies must reference Assemblies in the same or lower layers -- never higher layers.


## Resources ##

* [http://en.wikipedia.org/wiki/Circular_dependency](http://en.wikipedia.org/wiki/Circular_dependency)