Sentence:  In contrast, most data in the <WSD>deep Web</WSD> are structured data records stored in  backend database systems and there are usually no hyperlinks among these  data records. Due to the existence of extensive links among Web pages in the  surface ... 
Meaning of the word marked with <WSD> tags:  The portion of the (World Wide Web) that is not indexed by conventional (search engines). (from 2001)