Sentence:  There are close relationships between these items. For example, a syntax rule presented by text, and its corresponding concept illustrated by a cartoon have a close relation. Therefore, a function is needed to support the reference operation freely between closely related items. A <WSD>hyperstructure</WSD> is used to achieve this function. 
Meaning of the word marked with <WSD> tags:  A set of documents interlinked by hyperlinks, along with the links between documents.