These tags are similar in concept to the familiar HTML labels that help format text and other data on webpages.

BBC: NEWS | Technology | Yahoo makes semantic search shift

While most websites are currently built using version 4 of the Hyper Text Markup Language (HTML), that code is gradually being superseded by the newer version 5.

BBC: Web code weakness allows data dump on PCs

Where iRex shines isn't in book-formatted text, but in the no-nonsense business and legal documents: Word, HTML and above all, PDFs.

FORBES: E-Books