失效连结

失效连结，又称死链，是指超连结在经过一段时间后，不能再连接至原本档案、网页、服务器的现象。出现这种现象的原因有内容移动、管理人删除内容等等。

由于失效连结对资讯传播有着重大影响，所以研究者会以失效连结为题进行研究。该些研究各为连结失效率给出不同的答案。

失效率

研究者已就万维网的连结失效率进行研究。他们的研究范围涵盖引用网上内容的学术文献和数位图书馆馆藏。

一项于2003年发表的研究发现，在一星期内，平均每200条网上连结就会有1条成为失效连结^[1]，半衰期为138周。

另一项于2004年发表的研究则显示，某些网上连结（比如连接至某些档案类型的连结、由学术机构托管的连结）的半衰期可能异于其他连结^[2]。与一般网址相比，在出版物中出现的网址需经过更长时间才会失效。Weblock在2015年的一项研究中，分析了三间开放获取出版社的文集，并从中提取180,000个线上参考来源。最终发现该些连结的半衰期约有14年^[3]，这跟2005年的研究结果大致相符——它发现半数在《D-Lib杂志（英语：D-Lib Magazine）》中被引用的线上来源能够在10年后继续有效^[4]。另有研究显示，于学术文献中引用的线上来源拥有较高的失效机会，不过半衰期则达4年以上^[5]^[6]。《BMC生物信息学（英语：BMC Bioinformatics）》于2013年刊登了一篇研究报告，当中以Web of Science的摘要为研究对象，分析当中近15,000条连结。结果发现该些网页有50%在9.3年后继续有效，整体只有约6成有线上存档^[7]。

一项2002年的研究显示，与其他连结相比，于数位图书馆上出现的连结需较长时间才会失效^[8]。

成因

各种各样的原因都会令超连结失效。网站的管理人决定把网站删除便是一例。其他原因还有管理人把内容移动至新域名、网站所使用的技术过旧、没有更新域名注册信息^[9]、伺服器停止运作^[10]。

防止连结失效

防止连结失效的方法有尽可能使用没太大可能失效的连结、以各种方式保护现有连结免于失效、修复因内容移动或删除而失效的连结。当中最基本的方法就是创造出不会随时间而改变的网址^[11]。

张贴连结者可采取以下方法，以减低连结失效的机会：

不要张贴连接至研究者个人页面的连结^[4]
张贴简洁网址^[12]
张贴固定链接^[11]
尽可能张贴连接至网页的连结^[12]
张贴连接至互联网档案馆^[13]、WebCite^[14]、Archive.is、 Perma.cc^[15]、Amber^[16]等网络档案馆的连结

参见

延伸阅读

Markwell, John; Brooks, David W. Broken Links: The Ephemeral Nature of Educational WWW Hyperlinks. Journal of Science Education and Technology. 2002, 11 (2): 105–108. doi:10.1023/A:1014627511641.
Gomes, Daniel; Silva, Mário J. Modelling Information Persistence on the Web (PDF). Proceedings of the 6th International Conference on Web Engineering. ICWE'06. 2006 [2010-09-14]. （原始内容 (PDF)存档于2011-07-16）.
Dellavalle, Robert P.; Hester, Eric J.; Heilig, Lauren F.; Drake, Amanda L.; Kuntzman, Jeff W.; Graber, Marla; Schilling, Lisa M. Going, Going, Gone: Lost Internet References. Science. 2003, 302 (5646): 787–788 [2021-06-17]. PMID 14593153. doi:10.1126/science.1088234. （原始内容存档于2024-04-17）.
Koehler, Wallace. An Analysis of Web Page and Web Site Constancy and Permanence. Journal of the American Society for Information Science. 1999, 50 (2): 162–180. doi:10.1002/(SICI)1097-4571(1999)50:2<162::AID-ASI7>3.0.CO;2-B.
Sellitto, Carmine. The impact of impermanent Web-located citations: A study of 123 scholarly conference publications (PDF). Journal of the American Society for Information Science and Technology. 2005, 56 (7): 695–703 [2021-06-17]. doi:10.1002/asi.20159. （原始内容存档 (PDF)于2017-09-21）.

参考资料

^ Fetterly, Dennis; Manasse, Mark; Najork, Marc; Wiener, Janet. A large-scale study of the evolution of web pages. 2003 [2010-09-14]. （原始内容存档于2011-07-09）.
^ Koehler, Wallace. A longitudinal study of web pages continued: a consideration of document persistence. Information Research. 2004, 9 (2) [2019-01-31]. （原始内容存档于2017-09-11）.
^ All-Time Weblock Report. 2015 [2016-01-12]. （原始内容存档于2016-03-04）.
^ ^4.0 ^4.1 McCown, Frank; Chan, Sheffan; Nelson, Michael L.; Bollen, Johan. The Availability and Persistence of Web References in D-Lib Magazine (PDF). 2005 [2005-10-12]. （原始内容 (PDF)存档于2012-07-17）.
^ Spinellis, Diomidis. The Decay and Failures of Web References. Communications of the ACM. 2003, 46 (1): 71–77 [2007-09-29]. doi:10.1145/602421.602422. （原始内容存档于2020-07-23）.
^ Steve Lawrence; David M. Pennock; 加里·弗雷克; et al. Persistence of Web References in Scientific Research. 计算机 (杂志). 2001-03, 34 (3): 26–31. CiteSeerX 10.1.1.97.9695  . ISSN 0018-9162. doi:10.1109/2.901164. Wikidata Q21012586 （英语）.
^ Hennessey, Jason; Xijin Ge, Steven. A Cross Disciplinary Study of Link Decay and the Effectiveness of Mitigation Techniques. BMC Bioinformatics. 2013, 14: S5. PMC 3851533  . PMID 24266891. doi:10.1186/1471-2105-14-S14-S5.
^ Nelson, Michael L.; Allen, B. Danette. Object Persistence and Availability in Digital Libraries. D-Lib Magazine. 2002, 8 (1) [2019-09-24]. doi:10.1045/january2002-nelson  . （原始内容存档于2020-07-19）.
^ Kramer-Smyth, Jeanne. Partners for Preservation: Advancing digital preservation through cross-community collaboration. Facet Publishing. 2019: 70 [2021-06-17]. ISBN 9781783303472. （原始内容存档于2021-06-28）.
^ Bespalov, A.; Michel, M. C; Steckler, T. (编). Good Research Practice in Non-Clinical Pharmacology and Biomedicine. Springer Nature. 2020: 284 [2021-06-17]. ISBN 9783030336561. （原始内容存档于2021-06-28）.
^ ^11.0 ^11.1 Berners-Lee, Tim. Cool URIs Don't Change. 1998 [2019-01-31]. （原始内容存档于2000-03-02）.
^ ^12.0 ^12.1 Kille, Leighton Walter. The Growing Problem of Internet "Link Rot" and Best Practices for Media and Online Publishers. Journalist's Resource, Harvard Kennedy School. 2014-11-08 [2015-01-16]. （原始内容存档于2015-01-12）.
^ Internet Archive: Digital Library of Free Books, Movies, Music & Wayback Machine. 2001-03-10 [2013-10-07]. （原始内容存档于1997-01-26）.
^ Eysenbach, Gunther; Trudel, Mathieu. Going, going, still there: Using the WebCite service to permanently archive cited web pages. Journal of Medical Internet Research. 2005, 7 (5): e60. PMC 1550686  . PMID 16403724. doi:10.2196/jmir.7.5.e60.
^ Zittrain, Jonathan; Albert, Kendra; Lessig, Lawrence. Perma: Scoping and Addressing the Problem of Link and Reference Rot in Legal Citations (PDF). Legal Information Management. 2014-06-12, 14 (2): 88–99 [2020-06-10]. doi:10.1017/S1472669614000255. （原始内容存档 (PDF)于2020-11-01）.
^ Harvard University's Berkman Center Releases Amber, a "Mutual Aid" Tool for Bloggers & Website Owners to Help Keep the Web Available | Berkman Center. cyber.law.harvard.edu. [2016-01-28]. （原始内容存档于2016-02-02）.

[Fetterly2003-1] Fetterly, Dennis; Manasse, Mark; Najork, Marc; Wiener, Janet. A large-scale study of the evolution of web pages. 2003 [2010-09-14]. （原始内容存档于2011-07-09）.

[Koehler2004-2] Koehler, Wallace. A longitudinal study of web pages continued: a consideration of document persistence. Information Research. 2004, 9 (2) [2019-01-31]. （原始内容存档于2017-09-11）.

[3] All-Time Weblock Report. 2015 [2016-01-12]. （原始内容存档于2016-03-04）.

[McCown2005-4] 4.0 ^4.1 McCown, Frank; Chan, Sheffan; Nelson, Michael L.; Bollen, Johan. The Availability and Persistence of Web References in D-Lib Magazine (PDF). 2005 [2005-10-12]. （原始内容 (PDF)存档于2012-07-17）.

[Spinellis2003-5] Spinellis, Diomidis. The Decay and Failures of Web References. Communications of the ACM. 2003, 46 (1): 71–77 [2007-09-29]. doi:10.1145/602421.602422. （原始内容存档于2020-07-23）.

[Lawrence2001-6] Steve Lawrence; David M. Pennock; 加里·弗雷克; et al. Persistence of Web References in Scientific Research. 计算机 (杂志). 2001-03, 34 (3): 26–31. CiteSeerX 10.1.1.97.9695  . ISSN 0018-9162. doi:10.1109/2.901164. Wikidata Q21012586 （英语）.

[7] Hennessey, Jason; Xijin Ge, Steven. A Cross Disciplinary Study of Link Decay and the Effectiveness of Mitigation Techniques. BMC Bioinformatics. 2013, 14: S5. PMC 3851533  . PMID 24266891. doi:10.1186/1471-2105-14-S14-S5.

[Nelson2002-8] Nelson, Michael L.; Allen, B. Danette. Object Persistence and Availability in Digital Libraries. D-Lib Magazine. 2002, 8 (1) [2019-09-24]. doi:10.1045/january2002-nelson  . （原始内容存档于2020-07-19）.

[9] Kramer-Smyth, Jeanne. Partners for Preservation: Advancing digital preservation through cross-community collaboration. Facet Publishing. 2019: 70 [2021-06-17]. ISBN 9781783303472. （原始内容存档于2021-06-28）.

[10] Bespalov, A.; Michel, M. C; Steckler, T. (编). Good Research Practice in Non-Clinical Pharmacology and Biomedicine. Springer Nature. 2020: 284 [2021-06-17]. ISBN 9783030336561. （原始内容存档于2021-06-28）.

[Berners-Lee1998-11] 11.0 ^11.1 Berners-Lee, Tim. Cool URIs Don't Change. 1998 [2019-01-31]. （原始内容存档于2000-03-02）.

[Kille2014-12] 12.0 ^12.1 Kille, Leighton Walter. The Growing Problem of Internet "Link Rot" and Best Practices for Media and Online Publishers. Journalist's Resource, Harvard Kennedy School. 2014-11-08 [2015-01-16]. （原始内容存档于2015-01-12）.

[13] Internet Archive: Digital Library of Free Books, Movies, Music & Wayback Machine. 2001-03-10 [2013-10-07]. （原始内容存档于1997-01-26）.

[Eysenbach2005-14] Eysenbach, Gunther; Trudel, Mathieu. Going, going, still there: Using the WebCite service to permanently archive cited web pages. Journal of Medical Internet Research. 2005, 7 (5): e60. PMC 1550686  . PMID 16403724. doi:10.2196/jmir.7.5.e60.

[permacc-15] Zittrain, Jonathan; Albert, Kendra; Lessig, Lawrence. Perma: Scoping and Addressing the Problem of Link and Reference Rot in Legal Citations (PDF). Legal Information Management. 2014-06-12, 14 (2): 88–99 [2020-06-10]. doi:10.1017/S1472669614000255. （原始内容存档 (PDF)于2020-11-01）.

[16] Harvard University's Berkman Center Releases Amber, a "Mutual Aid" Tool for Bloggers & Website Owners to Help Keep the Web Available | Berkman Center. cyber.law.harvard.edu. [2016-01-28]. （原始内容存档于2016-02-02）.

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