Using identifiers allows specific elements to be distinguished within a digital book. These IDs must be unique within the document to ensure proper structure and behavior.

Objectives

• Prevent rendering and display issues.
• Ensure reliable access to specific identified elements.

Implementation

• Assign unique IDs to elements in the HTML code and ensure that no identifier is reused within the same page.

Control

• Check the source code of the EPUB Content Document to verify that no HTML identifier is used more than once.