Tag Tree Root
The Tag Tree has a root, called Tags. It is always the first tag in the Tag Tree.
The top-level tag is, Document, and is nested under the root, Tags.
The second level tag, nested under Document, is Part.
All other tags nest under the Part tag.
While there can be more than one Part tag, each Part tag must nest under the Document tag and each Part tag must be at the same nest level.
Do not nest a Part tag within a Part tag. Validation software considers nesting of Part tags to be a structural error.
Other Tags
Div and Sect tags must nest under a Part tag.
Tag Tree organization is recommended rather than having one long tree by using Div and Sect tags.
The Div tag is an abbreviation of, Division, and represents a major story line of a document.
The Sect (Section) tag also represents a major story and is the more commonly used tag. Frequently, an Sect tag is used for the tags of each page of a document or can match to each numbered section of a document.
Organizing tags by page or section assists when troubleshooting issues with tagging. Tag Tree order issues can occur when the Reading order is not the same as the tag order. When the Reading order is changed to match the logical order of the content on a page, the Tag Tree order will frequently need adjustment to be put back in logical order.
Note: Assistive Technology, such as Screen Reader software, uses the Tag Tree to determine reading order.