The more agreement there is, the better. For example, there are emerging standards for XML DTDs in specific domains. [...] If there is not agreement (e.g., only some Web sites include taxes in the price information), then effort is required to make sure that you have the right concepts at a given Web site. This creates more work in programming, e.g., one may need to create separate Web application modules for each site. This is made easier if the semantics of the terms and concepts at a given Web site are clearly specified (possibly informally). When there is not agreement and if the semantics of the terms are not clearly specified, there will be a lot of guesswork, thus undermining the reliability of applications. [...] Inspired by this analysis we conjecture that the following is a law of the semantic web: “The more agreement there is, the less it is necessary to have machine processable semantics.”