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| Web resources that are intended for the whole public, the University of California system, or all of UCSB should be referenced by URIs that do not change. Examples of these global resources include campus maps, visitor resources, UCSB policies pages, major department/division home pages, official UCSB artwork, and the like. |
| When URIs change, old bookmarks and search engine results become obsolete. The information becomes more difficult to find, less prominent, and creates a maintenance burden for all other sites and pages referring to them. |
Instead, create URIs that "don't go away." The following recommendations will make these resources more useful as permanent bookmarks and more easy to access from search engines. Of course, always test your links after making any changes.
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Recommendations for Building a Persistent URI
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- Don't include file extensions that expose or require a media type. Although Web servers have been delivering html files from the beginning, future Web servers may, for example, deliver xml or xhtml files of various versions. Many browsers will attempt to map the file extension (after the last period) to a file type. Then if your framework or technology changes, all the URIs with file extensions will have to change.
Example
Original URL: http://www.department.ucsb.edu/webguide/index.shtml
Persistent URI: http://www.ucsb.edu /webguide
- Don't include anything in your URI that is specific to a programming language or platform, such as .pl, .php, .jsp, servlet, cgi-bin etc. Presentation technologies may change, but the data (or purpose of the data) will not
Example
Original URL: http://www.department.ucsb.edu/archives/index.php
Persistent URI: http://www.department.ucsb.edu/archives
- Do not hint at whether the global resource page is static or dynamically generated. As in item 1, URL parameters passed in dynamically generated pages (i.e, pages whose URIs include a ? and & characters with text) are subject to change.
Example
Original URL: http://www.department.ucsb.edu/cgi-bin/calendar.cgi?month=7&events=all
Persistent URI: http://www.department.ucsb.edu /current-events
- Try to avoid a trailing "/" in your persistent URI so that users never have to consider whether the URL requires it or not.
Example
Original URL: http://www.department.ucsb.edu/faculty/
Persistent URI: http://www.department.ucsb.edu/faculty
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Techniques for Creating Persistent URIs
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Rewrite the URI on the Server
The best solution is to have the URI rewritten on your server. The technique will vary according to
your platform or programming language. The Apache Web server, for example, has powerful features to help
you do this and it can be installed as a proxy in front of many other Web applications.
To illustrate with the example from Item 3 above: when receiving a request for "/current-events",
the server at www.department.ucsb.edu will rewrite the URI to "/cgi- bin/calendar.cgi?month=7&events=all".
Users will only see the persistent form of the URI which they can bookmark, while the server can use the
existing script and rewrite the request to include the current month, etc.
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Maintain a Redirect Page in a Permanent Location
A simpler solution for making a persistent URI is to create a redirect page in a location you know will
not change (set, for example, as the default page in a directory created for the purpose). If the URL of
your global resource page changes, you simply update the redirect page.
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Use Redirects When Long-Lived URLs Change
Finally, consider using a redirect whenever you change the location of a global resource that has been
available at one URL for a long period of time, since that URL will effectively have functioned as a
"persistent link" itself.
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References
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