Example for Checkpoint
13.2 - Provide metadata to add semantic information to pages and sites.

One of the major issues of the World Wide Web as it exists today is that it is really hard to automate any tasks that one has to perform on the web. So far, the web is mainly built as a forum for human interaction; because most web documents are written for human consumption, the only available form of searching on the web (for example) is to simply match words or sentences contained in documents. Anyone who has used a web search service like AltaVista or HotBot knows that typing in a few keywords and receiving a couple of thousand "hits" is not necessarily very useful. A lot of manual "weeding" of information has to happen after that; it may also happen that the keywords for which you are searching are not prominent in the relevant document itself.

A possible solution for the search problem - and for the general issue of letting automated "agents" roam the web performing useful tasks - is to provide a mechanism that allows a more precise description of things on the web. This, in turn, could elevate the status of the web from machine-readable to something we might call machine-understandable.

Metadata is "data about data" or specifically in our current context "data describing web resources." The distinction between "data" and "metadata" is not an absolute one; it is a distinction created primarily by a particular application ("one application's metadata is another application's data").

From: Introduction to RDF Metadata - W3C NOTE 1997-11-13
http://www.w3.org/TR/NOTE-rdf-simple-intro

To Checkpoints for Guideline 13.