Editing Cross-cutting concern

{{Short description|Concept in aspect-oriented software development}}
In [[aspect-oriented software development]], '''cross-cutting concerns''' are [[Aspect (computer programming)|aspects]] of a [[computer program|program]] that affect several [[Modular programming|modules]], without the possibility of being [[Encapsulation (computer programming)|encapsulated]] in any of them.
These [[Concern (computer science)|concerns]] often cannot be cleanly [[Modularity (programming)|decomposed]] from the rest of the system in both the design and implementation, and can result in either ''scattering'' ([[code duplication]]), ''tangling'' (significant dependencies between systems), or both.

For instance, if writing an [[application software|application]] for handling [[Electronic health record|medical records]], the indexing of such records is a [[core concern]], while [[Data logging|logging]] a history of changes to the record database or user database, or an authentication system, would be cross-cutting concerns since they interact with more parts of the program.

==Background==
Cross-cutting concerns are parts of a program that rely on or must affect many other parts of the system. They form the basis for the development of [[aspect (computer science)|aspects]].<ref name="Patent 4">{{harvnb|Kiczales et al.|2002|p=4}}</ref> Such cross-cutting concerns do not fit cleanly into [[object-oriented programming]] or [[procedural programming]].<ref name="Seminal 1">{{harvnb|Kiczales|Lamping|Mendhekar|Maeda|1997|p=1}}</ref>

Cross-cutting concerns can be directly responsible for ''tangling'', or system inter-dependencies, within a [[computer program|program]]. Because procedural and [[functional language]] constructs consist entirely of procedure calling, there is no semantic through which two goals (the capability to be implemented and the related cross-cutting concern) can be addressed simultaneously.<ref name="Seminal 6">{{harvnb|Kiczales|Lamping|Mendhekar|Maeda|1997|p=6}}</ref> As a result, the code addressing the cross-cutting concern must be ''scattered'', or duplicated, across the various related locations, resulting in a loss of [[modularity (programming)|modularity]].<ref name="Seminal 1" />

[[Aspect-oriented programming]] aims to [[encapsulation (computer science)|encapsulate]] cross-cutting concerns into [[aspect (computer science)|aspects]] to retain modularity. This allows for the clean isolation and reuse of code addressing the cross-cutting concern.<ref name="Seminal 2">{{harvnb|Kiczales|Lamping|Mendhekar|Maeda|1997|p=2}}</ref> By basing designs on cross-cutting concerns, [[software engineering]] benefits can include modularity and simplified maintenance.<ref name="Li 1">{{harvnb|Li|Krishnamurthi|Fisler|2002|p=1}}</ref>

==Examples==
Examples of concerns that tend to be cross-cutting include:

* [[Business rule]]s
* [[Cache (computing)|Caching]]
* [[Code mobility]]
* [[Data validation]]
* Domain-specific [[Optimization (computer science)|optimizations]]
* [[Environment variables]] and other global configuration settings
* [[Error detection and correction]]
* [[Internationalization and localization]] which includes [[Language localisation]]
* [[Information security]]
* [[Log file|Logging]]
* [[Memory management]]
* [[Observer pattern|Monitoring]]
* [[Persistence (computer science)|Persistence]]
* [[Feature interaction problem|Product features]]
* [[Real-time computing|Real-time constraints]]
* [[Synchronization (computer science)|Synchronization]]
* [[Transaction processing]]
* [[Context-sensitive help]]
* [[Privacy]]
* [[Computer security]]

==See also==
* [[Separation of concerns]]
* [[Aspect-oriented programming]]
* [[Code refactoring]] (restructuring software)
* [[Database normalization]] (minimize needlessly replicated data)
* [[Multiple inheritance]]
* [[Microservices]]
* [[Orthogonalization]] (mathematical normalization)

==References==
{{reflist}}

==Bibliography==
{{sfn whitelist|CITEREFKiczales_et_al.2002}} 
*{{cite journal|last1=Kiczales|first1=Gregor|last2=Lamping|first2=John|last3=Mendhekar|first3=Anurag|last4=Maeda|first4=John|last5=Lopes|first5=Cristina|last6=Longtier|first6=Jean-Marc|last7=Irwin|year=1997|title=Aspect-Oriented Programming|journal=Proceedings of the 11th European Conference on Object-Oriented Programming (ECOOP 1997)|pages=220–242}}
*{{US patent reference|number=6467086|y=2002|m=10|d=15| inventor = Kiczales et al.|title = [[Aspect-oriented programming]]|ref={{sfnref|Kiczales et al.|2002}}}}
*{{cite journal|title=Verifying Cross-Cutting Features as Open Systems|last1=Li|first1=Harry|first2=Shriram|last2=Krishnamurthi|first3=Kathi|last3=Fisler|journal=ACM SIGSOFT Software Engineering Notes|volume=27|issue=6|year=2002|pages=89–98|doi=10.1145/605466.605481|citeseerx=10.1.1.8.9445|s2cid=52835673}}
*{{cite journal|last1=Parnas|first1=David L.|date=December 1972|title=On the Criteria To Be Used in Decomposing Systems into Modules|journal=[[Communications of the ACM]]|volume=15|issue=12|pages=1053–1058|citeseerx = 10.1.1.90.8963|doi=10.1145/361598.361623 |s2cid=53856438}}
*{{cite book|last1=Tarr|first1=Peri|last2=Ossher|first2=Harold|last3=Harrison|first3=William|first4=Stanley M. Jr.|last4=Sutton|chapter=N degrees of separation: Multi-dimensional separation of concerns |year=1999|title=Proceedings of the 1999 International Conference on Software Engineering (IEEE Cat. No.99CB37002)|location=Los Angeles, California, USA|publisher=[[IEEE Computer Society Press]]|pages=107–119|doi=10.1109/ICSE.1999.841000|citeseerx = 10.1.1.89.1641 |isbn=978-1-58113-074-4}}

==Further reading==
*Laddad, R. (2003): AspectJ in Action, Practical Aspect-Oriented Programming, Manning Publications Co.

==External links==
*[https://web.archive.org/web/20150919015041/http://www.aosd.net/wiki/index.php?title=Glossary AOSD.net's] glossary of [[aspect-oriented programming|aspect oriented]] terms (via [https://web.archive.org/web/20150919015041/http://www.aosd.net/wiki/index.php?title=Glossary Internet Archive Wayback Machine]; AOSD.net has become [http://modularity.info/ Modularity]).
*[[AspectJ]] [http://eclipse.org/aspectj/], an Aspect-Oriented extension to the [[Java (programming language)|Java programming language]]
*Bergmans, L., M. Aksit (2001): Composing Multiple Concerns Using Composition Filters, https://web.archive.org/web/20170909131212/http://trese.cs.utwente.nl/ (24 July 2004)
*Berg, K. van den, Conejero, J. and Chitchyan, R. (2005). AOSD Ontology 1.0 ‐ Public Ontology of Aspect‐Orientation. AOSD Europe Network of Excellence, http://eprints.eemcs.utwente.nl/10220/01/BergConChi2005.pdf
*Here is an example of handling a cross-cutting concern: https://web.archive.org/web/20161220151503/https://www.captechconsulting.com/blogs/a-persistence-pattern-using-threadlocal-and-ejb-interceptors

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[[Category:Aspect-oriented software development]]
[[Category:Aspect-oriented programming]]