MWI Team Blog

This post is the second post of the One Web series, and tours the two principles and five good practices of the architecture of the Web that yield the core of One Web. It does stay on the theory side, but note it comes with small and handy figures :) Part 3 is now available.

A Web of URIs

The Architecture of the World Wide Web specification defines the Web as an information space in which the items of interest, referred to as resources, are identified by global identifiers called Uniform Resource Identifiers (URI). Hey, where are the links? Links are but a direct consequence of the use of global identifiers: any resource of the Web can link to any other resource, because each resource is precisely identified by its global identifier.

The global identifiers could have taken different forms. They happen to be URIs in practice. All linking mechanisms on the Web use URIs. URIs are identifiers, and should be regarded as such. In particular, they do not carry any information on the resource itself.

Links equal value

The value of the Web lies in its ability to link similar resources together, either through explicit links between the resources, or through implicit links (e.g. two resources targeting the same resource, two resources that match the same keyword search in a search engine). The value of the Web could be defined as the sum of the values of its resources.

The value of the Web is reduced each time a resource escapes or divides the Web. This happens when:

• Resources are identified with global identifiers that are not URIs as it de facto creates another Web and divides the information space into different spaces that cannot inter-communicate.

  Good practice: Identify resources with URIs

• A single URI identifies more than one resource. Resources identified by the URI are hidden from the rest of the world that can only link to the visible URI.

  Good practice: Use distinct URIs to identify distinct resources

  Example
  If we add two resources hidden behind resource A, we cannot tell whether resources B and C link to A or to one of the other resources. The value of A is reduced, say, to 2. The total value of the Web is reduced to 4.
  

• The URI of a resource changes. When a URI changes, links that used the previous URI are broken, reducing the value of the resources that contain the broken links. Cool URIs don't change!

  Good practice: URIs should be persistent

  Example
  When the URI of resource A changes, resources B and C now link to nothing. The value of resource A is reduced to 0. The total value of the Web is reduced to 2.
  

• The type of information carried out by a resource changes. Links to the resource are still valid, but their value is reduced because they now link to a different resource.

  Good practice: Resources should return predictable information

  This good practice does not mean that the content in itself cannot change. The actual content of a resource that returns "breaking news information about strikes in France" is likely to change pretty often, but it should always return "breaking news information about strikes in France".

  Example
  If the URI that used to identify resource A now identifies resource D, resources B and C now link to something by mistake. The value of resource D is simply 0. The total value of the Web is reduced to 2.
  

• Different URIs are used to identify the same resource. In this case, the problem arises because different resources that link to the resource will use different URIs, creating artificial copies of the resource.

  Good practice: Do not use different URIs to identify the same resource

  Example
  If resource A is identified by two different URIs, and resource B links to resource A using the first URI, while resource C uses the second URI, resources B and C now apparently link to two different copies of resource A and are not connected anymore. Their respective value is 0.
  
  Resource A is duplicated. One copy is the target of one link originating from resource B, the other from resource C. Each copy has thus a value of 1. The total value of the Web was reduced from 6 to 2!

One Web is NOT One Version

There is one important message that the One Web vision does not carry: an hypothetical need to return the same version for each and every device. A Web site may use content adaptation, i.e. return different versions of a resource depending on the capabilities of the device and/or the context of the user. In fact, content adaptation is explicitly encouraged to improve the user experience on devices. Exploit devices capabilities is one of the mobile web best practices, and it does fit One Web!

How many versions should there be? 1, 10, 100, 1000? Content authors will certainly want to reduce the number of versions they have to maintain to a bare minimum, to one whenever possible. With a little bit of (hard) work and the possible help of content adaptation tools, it is usually possible to generate all versions from one single source. Could this single source be served to everyone so that we could simply drop the need to adapt the content? In some cases, yes. The Web site of the W3C Mobile Web Initiative for instance does not use content adaptation (but for one or two exceptions that are out of scope of this post) and was designed to work on a majority of devices. One may argue that the content of this Web site is "simple". As of today, it is true that specific versions are required to take advantage of the specificities of various devices. I'll get back to that in the last part of this series. The one thing that I would like to stress out here is that One Web is neutral when it comes to specifying how many versions there should be, provided that the good practices mentioned above are applied, of course!

Fine. Now you know One Web. How does that connect to the real-world?

[On to part 3...]