THead

Description	Defines the header section of a table, containing cells that label the columns or rows and provide context for the table data.
Namespace	1.7 2.0
Category	block

Attributes

Placement

Specifies how the element is placed relative to surrounding content (e.g., block-level or inline flow).

WritingMode

Defines the direction of text flow (e.g., left-to-right, right-to-left, or vertical).

BackgroundColor

Sets the background color for the element’s content area.

BorderColor

Specifies the color of the border around the element.

BorderStyle

Indicates the style of the border (e.g., solid, dashed, dotted).

BorderThickness

Defines the thickness of the border line in user space units (such as points).

Padding

Determines the space between the element’s border (or boundary) and its inner content.

Color

Applies the primary color (fill or stroke) for the text or graphic content.

BBox

Width

Declares an explicit width for the element in user space units.

Height

Declares an explicit height for the element in user space units.

role

Main indicator of type. This semantic association allows tools to present and support interaction with the object in a manner that is consistent with user expectations about other objects of that type.

Differences

Well tagged PDF:

The 'THead' element in Well-Tagged PDF is used to group header rows in a table, providing a clear separation from the table body.

It should enclose all header rows and be distinctly separated from the body ('TBody') and footer ('TFoot') sections to preserve table semantics.

PDFUA:

In PDF/UA, the 'THead' element enhances accessibility by clearly delineating the header section of a table, which is essential for establishing context.

The header group must be tagged and associated with corresponding data cells, ensuring that assistive technologies can reliably convey the table's structure.