The Future

2.6 The Future

URLs are a powerful tool. Their design allows them to name all existing objects and easily encompass new formats. They provide a uniform naming mechanism that can be shared between Internet protocols.

However, they are not perfect. URLs are really addresses, not true names. This means that a URL tells you where something is located, for the moment. It provides you with the name of a specific server on a specific port, where you can find the resource. The downfall of this scheme is that if the resource is moved, the URL is no longer valid. And at that point, it provides no way to locate the object.

What would be ideal is if you had the real name of an object, which you could use to look up that object regardless of its location. As with a person, given the name of the resource and a few other facts, you could track down that resource, regardless of where it moved.

The Internet Engineering Task Force (IETF) has been working on a new standard, uniform resource names (URNs), for some time now, to address just this issue. URNs provide a stable name for an object, regardless of where that object moves (either inside a web server or across web servers).

Persistent uniform resource locators (PURLs) are an example of how URN functionality can be achieved using URLs. The concept is to introduce another level of indirection in looking up a resource, using an intermediary resource locator server that catalogues and tracks the actual URL of a resource. A client can request a persistent URL from the locator, which can then respond with a resource that redirects the client to the actual and current URL for the resource (see Figure 2-6). For more information on PURLs, visit http://purl.oclc.org.

Figure 2-6. PURLs use a resource locator server to name the current location of a resource

figs/http_0206.gif

2.6.1 If Not Now, When?

The ideas behind URNs have been around for some time. Indeed, if you look at the publication dates for some of their specifications, you might ask yourself why they have yet to be adopted.

The change from URLs to URNs is an enormous task. Standardization is a slow process, often for good reason. Support for URNs will require many changesconsensus from the standards bodies, modifications to various HTTP applications, etc. A tremendous amount of critical mass is required to make such changes, and unfortunately (or perhaps fortunately), there is so much momentum behind URLs that it will be some time before all the stars align to make such a conversion possible.

Throughout the explosive growth of the Web, Internet userseveryone from computer scientists to the average Internet userhave been taught to use URLs. While they suffer from clumsy syntax (for the novice) and persistence problems, people have learned how to use them and how to deal with their drawbacks. URLs have some limitations, but they're not the web development community's most pressing problem.

Currently, and for the foreseeable future, URLs are the way to name resources on the Internet. They are everywhere, and they have proven to be a very important part of the Web's success. It will be a while before any other naming scheme unseats URLs. However, URLs do have their limitations, and it is likely that new standards (possibly URNs) will emerge and be deployed to address some of these limitations.

 



HTTP. The Definitive Guide
HTTP: The Definitive Guide
ISBN: 1565925092
EAN: 2147483647
Year: 2001
Pages: 294

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