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Editor's Note: References to scholar.cc.emory.edu and shemesh.scholar.emory.edu in this article are outdated. See more recent TC Notes for updated information.
One of the problems with Web publishing is the fact that many Web pages seem to be here today, gone tomorrow. Sometimes authors decide to remove their pages from the server, but in other instances, the page is still there, but its URL (Web address) has changed. URLs can change for a variety of reasons: a page is incorporated into different set of Web pages, an Internet service provider changes its basic URL, a set of pages is moved from one Internet site to another more or less intact.
Persistent URLs (PURLs) were designed to alleviate the problem of the missing Web page. Once a PURL is assigned, it never changes, regardless of whether the Web page in question changes its name or moves to an entirely different site. PURLs are actually entries in a database on a PURL server site. Each PURL is associated in the database with a URL, and the maintainer of a specific PURL is responsible for ensuring that the PURL table is updated properly if a URL changes. For more information on PURLs, see the PURL Home Page.
To ensure that interested people will always be able to find TC articles, reviews, and other Web pages, regardless of the vicissitudes of life on the Web, TC now has a new Web address: http://purl.org/TC, a Persistent URL. This address points to the TC home page, but all other TC pages may also be accessed using the PURL rather than the old addresses (http://scholar.cc.emory.edu../TC.html or http://shemesh.scholar.emory.edu../TC.html).
Many people have asked, and probably more have wondered, why TC has two different addresses, one with scholar in the URL and the other containing shemesh. Since its inception, TC has resided on the server that runs TELA, the Scholars Press World Wide Web site. The computer that hosted TELA was originally housed on the main campus of Emory University, in the same building as the computer center, and it was assigned the address scholar.cc.emory.edu. At the beginning of 1997, TELA was transferred to a new, bigger computer at Scholars Press, on the edge of the Emory campus, because the Press had recently been connected by fiber optic cable to the Internet. The computer containing TELA was now in a different subnet of the Emory University domain, scholar.emory.edu (rather than cc.emory.edu), so it was assigned a new address: shemesh.scholar.emory.edu. The old address scholar.cc.emory.edu was retained as an alias, so both addresses work for all pages on the TELA site, including the TC pages. The PURL address http://purl.org/TC is associated with the "real" machine address http://shemesh.scholar.emory.edu../TC.html rather than the scholar alias. No one can guarantee that the current URL associated with TC will remain the same in perpetuity, but users who use the new PURL address will not have to worry about changing URLs. TC will always be available at http://purl.org/TC.