I think in a way it has, just not in the purist sense that Semantic Web proponents have advocated. Microformats, semantic HTML tags, and non-rendered meta-data

I think in a way it has, just not in the purist sense that Semantic Web proponents have advocated. Microformats, semantic HTML tags, and non-rendered meta-data can be found all over the place. Especially in eCommerce. What hasn't caught on is the formal language of the semantic web. And for that my hypothesis is that it is so formal and so strict that it produces a barrier of entry that is too high for non-academics. RDF has a bit of a leaning curve compared to competing technologies. Furthermore, FOAF (Friend of a Friend) last time I looked at it had a lot of outdated domain specific tags. For example, there is a tag for ICQ (an instant messenger practically no one uses anymore but was very popular in the 90s) but no tags for new technology rather than, say, having generic tags that can be used for any messenger system and using attributes. Summary: - High barrier of entry - Easier to use alternatives - It hasn't really failed, it's just taken a form that is more friendly for day-to-day Edit: Also, if you go the Semantic Web Meetup in Cambridge there are a lot of talks of the medical industry, database industry, and things like that which show it is alive https://www.meetup.com/The-Cambridge-Semantic-Web-Meetup-Group/events/232572089/ https://www.meetup.com/The-Cambridge-Semantic-Web-Meetup-Gro...