Cross Cutting Concern

A cross-cutting concern is some software concern (synchronization, logging, memory allocation, NetworkTransparency?, UI preferences) that is for the most part outside of (and orthogonal to) the ProblemDomain a software component/module is concerned with, but important nonetheless. Many different techniques have been developed to deal with these--some good, some bad, some UgLy.

Techniques include:

TemplateMetaprogramming, augmented with PolicyObject?s (such as StandardTemplateLibrary allocators)
MetaObjectProtocols, in particular things like before functions, after functions, etc.
Decorators (both DecoratorPattern and the language feature in Java), delegation in general.
TemplateMethodPattern (i.e. use of HookMethods)
RPC tools
Many of the CreationalPatterns can be used to allow variation of some cross-cutting concern at runtime.
MultipleInheritance and MixIns
ContextObject or ExplicitManagementOfImplicitContext

A programming paradigm dealing with this stuff is AspectOrientedProgramming.

A few bad techniques for dealing with CrossCuttingConcerns? include:

GrandCentralStation (aggregating lots of independent domain functionality into a BigBallOfMud just so the CrossCuttingConcern(s) can be dealt with in one place).

CategoryComplexity, CategoryInfoPackaging CategoryAspectOrientation