失效链接

失效链接，又称死链，是指超链接在经过一段时间后，不能再连接至原本文件、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。

由于失效链接对信息传播有着重大影响，所以研究者会以失效链接为题进行研究。该些研究各为链接失效率给出不同的答案。

失效率

研究者已就万维网的链接失效率进行研究。他们的研究范围涵盖引用网上内容的学术文献和数字图书馆馆藏。

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

另一项于2004年发表的研究则显示，某些网上链接（比如连接至某些文件类型的链接、由学术机构托管的链接）的半衰期可能异于其他链接^[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个在线参考来源。最终发现该些链接的半衰期约有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》中被引用的在线来源能够在10年后继续有效^[4]。另有研究显示，于学术文献中引用的在线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》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条链接。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成有在线存档^[7]。

一项2002年的研究显示，与其他链接相比，于数字图书馆上出现的链接需较长时间才会失效^[8]。

成因

各种各样的原因都会令超链接失效。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]、服务器停止运作^[10]。

防止链接失效

防止链接失效的方法有尽可能使用没太大可能失效的链接、以各种方式保护现有链接免于失效、修复因内容移动或删除而失效的链接。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]。

张贴链接者可采取以下方法，以减低链接失效的机会：

不要张贴连接至研究者个人页面的链接^[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链接^[12]
张贴连接至互联网档案馆^[13]、WebCite^[14]、Archive.is、 Perma.cc^[15]、Amber^[16]等网络档案馆的链接

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].
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. PMID 14593153. doi:10.1126/science.1088234.
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.

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].
↑ Koehler, Wallace. A longitudinal study of web pages continued: a consideration of document persistence. Information Research. 2004, 9 (2) [2019-01-31].
↑ All-Time Weblock Report. 2015 [2016-01-12].
↑ ^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].
↑ 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.
↑ 警告：模板链接：{{Cite Q}}模板已经停止使用。本来源对应的Wikidata数据项目为： Q21012586
↑ 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 .
↑ Kramer-Smyth, Jeanne. Partners for Preservation: Advancing digital preservation through cross-community collaboration. Facet Publishing. 2019: 70. ISBN 9781783303472.
↑ Bespalov, A.; Michel, M. C; Steckler, T. (编). Good Research Practice in Non-Clinical Pharmacology and Biomedicine. Springer Nature. 2020: 284. ISBN 9783030336561.
↑ ^11.0 ^11.1 Berners-Lee, Tim. Cool URIs Don't Change. 1998 [2019-01-31].
↑ ^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].
↑ Internet Archive: Digital Library of Free Books, Movies, Music & Wayback Machine. 2001-03-10. 缺少或|url=为空 (帮助);
↑ 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.
↑ 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].

[Fetterly2003-1] Fetterly, Dennis; Manasse, Mark; Najork, Marc; Wiener, Janet. A large-scale study of the evolution of web pages. 2003 [2010-09-14].

[Koehler2004-2] Koehler, Wallace. A longitudinal study of web pages continued: a consideration of document persistence. Information Research. 2004, 9 (2) [2019-01-31].

[3] All-Time Weblock Report. 2015 [2016-01-12].

[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].

[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.

[Lawrence2001-6] 警告：模板链接：{{Cite Q}}模板已经停止使用。本来源对应的Wikidata数据项目为： Q21012586

[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 .

[9] Kramer-Smyth, Jeanne. Partners for Preservation: Advancing digital preservation through cross-community collaboration. Facet Publishing. 2019: 70. ISBN 9781783303472.

[10] Bespalov, A.; Michel, M. C; Steckler, T. (编). Good Research Practice in Non-Clinical Pharmacology and Biomedicine. Springer Nature. 2020: 284. ISBN 9783030336561.

[Berners-Lee1998-11] 11.0 ^11.1 Berners-Lee, Tim. Cool URIs Don't Change. 1998 [2019-01-31].

[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].

[13] Internet Archive: Digital Library of Free Books, Movies, Music & Wayback Machine. 2001-03-10. 缺少或|url=为空 (帮助);

[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.

[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].

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