Table 340 – Standard structure types for illustration elements

Structure Type

Description

Figure

(Figure) An item of graphical content. Its placement may be specified with the Placement layout attribute (see “General Layout Attributes” in 14.8.5.4, “Layout Attributes” ).

Formula

(Formula) A mathematical formula.

This structure type is useful only for identifying an entire content element as a formula. No standard structure types are defined for identifying individual components within the formula. From a formatting standpoint, the formula shall be treated similarly to a figure (structure type Figure).

Form

(Form) A widget annotation representing an interactive form field (see 12.7, “Interactive Forms” ). If the element contains a Role attribute, it may contain content items that represent the value of the (non-interactive) form field. If the element omits a Role attribute (see Ta b l e 348 ), it shall have only one child: an object reference (see 14.7.4.3, “PDF Objects as Content Items” ) identifying the widget annotation. The annotations’ appearance stream (see 12.5.5, “Appearance Streams” ) shall describe the appearance of the form element.