Typical electronic business applications need to make queries about products and services made available by sellers and service providers through the Web. Unfortunately, it can be a very time consuming task to discover information as simple as those, since every site has its own metaphore. The so-called search engines can facilitate such task because a client provides some keywords and obtain a list of Uniform Resource Locators (URL) that point to the target sites, but it does not prevent from interacting with each site. We propose and define a novel kind of service for the Web: the semantic search engine. Differently from traditional search engines, a semantic search engine stores semantic information about Web resources and is able to solve complex queries, considering as well the context where the Web resource is targeted. We show, through examples, how a semantic search engine may be employed in order to permit clients obtain information about commercial products and services, as well as about sellers and service providers which can be hierarchically organized. Semantic search engines may seriously contribute to the development of electronic business applications since it is based on strong theory and widely accepted standards.