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The Wayback Machine is a digital archive of the World Wide Web and other information on the Internet created by the Internet Archive, a nonprofit organization, based in San Francisco, California, United States. It was set up by Brewster Kahle and Bruce Gilliat, and is maintained with content from Alexa Internet. The service enables users to see archived versions of web pages across time, which the archive calls a "three dimensional index." Since 1996, they have been archiving cached pages of web sites onto their large cluster of Linux nodes. They revisit sites every few weeks or months and archive a new version if the content has changed. The intent is to capture and archive content that otherwise would be lost whenever a site is changed or closed down. Their grand vision is to archive the entire Internet.〔(【引用サイトリンク】url=http://cachedpages.net/ )〕 The name ''Wayback Machine'' was chosen as a droll reference to a plot device in an animated cartoon series, ''The Rocky and Bullwinkle Show.'' In one of that animated cartoon's component segments, ''Peabody's Improbable History,'' lead characters Mr. Peabody and Sherman routinely used a time machine called the "WABAC machine" (pronounced ''wayback'') to witness, participate in, and, more often than not, alter famous events in history. ==Origins, growth, and storage capabilities== In 1996 Brewster Kahle, with Bruce Gilliat, developed software to crawl and download all publicly accessible World Wide Web pages, the Gopher hierarchy, the Netnews (Usenet) bulletin board system, and downloadable software. The information collected by these "crawlers" does not include all the information available on the Internet, since much of the data is restricted by the publisher or stored in databases that are not accessible. These "crawlers" also respect the robots exclusion standard for websites whose owners opt for them not to appear in search results or be cached. To overcome inconsistencies in partially-cached web sites, Archive-It.org was developed in 2005 by the Internet Archive as a means of allowing institutions and content creators to voluntarily harvest and preserve collections of digital content, and create digital archives. Information had been kept on digital tape for five years, with Kahle occasionally allowing researchers and scientists to tap into the clunky database. When the archive reached its fifth anniversary, it was unveiled and opened to the public in a ceremony at the University of California-Berkeley. Snapshots usually become available more than six months after they are archived or, in some cases, even later; it can take twenty-four months or longer. The frequency of snapshots is variable, so not all tracked web site updates are recorded. Sometimes there are intervals of several weeks or years between snapshots. After August 2008 sites had to be listed on the Open Directory in order to be included. According to Jeff Kaplan of the Internet Archive in November 2010, other sites were still being archived,〔(Archive.org forum thread with response by Jeff Kaplan ), last update November 07, 2010〕 but more recent captures would become visible only after the next major indexing, an infrequent operation. the Wayback Machine contained approximately three petabytes of data and was growing at a rate of 100 terabytes each month; the growth rate reported in 2003 was 12 terabytes/month. The data is stored on PetaBox rack systems manufactured by Capricorn Technologies. In 2009 the Internet Archive migrated its customized storage architecture to Sun Open Storage, and hosts a new data center in a Sun Modular Datacenter on Sun Microsystems' California campus. In 2011 a new, improved version of the Wayback Machine, with an updated interface and fresher index of archived content, was made available for public testing.〔(【引用サイトリンク】url=http://iawebarchiving.wordpress.com/2011/01/24/updated-wayback-machine-in-beta-testing/ )〕 In March 2011 it was said on the Wayback Machine forum that "The Beta of the new Wayback Machine has a more complete and up-to-date index of all crawled materials into 2010, and will continue to be updated regularly. The index driving the classic Wayback Machine only has a little bit of material past 2008, and no further index updates are planned, as it will be phased out this year." In January 2013 the company announced a ground-breaking milestone of 240 billion URLs. In October 2013 the company announced the "Save a Page" feature which allows any Internet user to archive the contents of a URL. This became a threat of abuse by the service for hosting malicious binaries. As of December 2014 the Wayback Machine contained almost nine petabytes of data and was growing at a rate of about 20 terabytes each week.〔(【引用サイトリンク】url=https://archive.org/about/faqs.php )〕 Between October 2013 and March 2015 the website's global Alexa rank changed from 162 to 208. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Wayback Machine」の詳細全文を読む スポンサード リンク
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