1. "It always seemed a bit ironic to me that Berners–Lee, who overthrew many of the most cherished tenets of both hypertext theory and SGML [standardised general mark–up language, a precursor to HTML or hypertext mark–up language] with his ‘less is more and worse is better‘ implementation of ideas from both in the world wide web, has been deeply enmeshed in a theoretical exercise rather than just celebrating the bottom–up activity that will ultimately result in the semantic web." Berners–Lee did concede that as with the world wide web, the semantic web should "serve useful stuff". "One of the problems we‘ve actually had with the semantic web, I only recently realised, is we haven‘t been doing that." Not enough useful RDF data has been left online, he explained: "The whole value–add of the web is serendipitous re–use: when you put it out there for one person, and it gets used by who–knows–who.