Krzysztof Janowicz (the person behind (Semantic) Similarity-Blog) is working on Sim-DL – Semantic Similarity Measurement Theory for the Description Logic ALCNR. In my eyes the notion of similarity is a good thing for search on the Semantic Web:

Currently, there is a lot of work going on in the development of query languages for the Semantic Web, see SPARQL for example. With these query languages you specify a query and an interpreter will return you those parts of an RDF graph exactly matching your query. This is a different search paradigm that we are used from search engines like Google. There, you enter a query and you will get results similar to that query, with the documents ranked highest that are most similar to it. Ranking by relevance is something not possible in SPARQL, as every results returned is equally relevant.