Here's another semantic search tool for Web application developers: Picky, a "a semantic text search engine for categorized data, such as varchar fields from a database." It's written in Ruby and you can grab the source here.
The developer, Florian Hanke, emphasizes that Picky is not a replacement for for full text search engines like Sphinx and Lucene. It's just for searching small, structured data very quickly.
The features include:
You can find out more on the features page.