Type of element that is the target of the cross-reference (for example, “figure”, “author-note”, “bibliographic-reference”). The values may be used for type-specific processing or validation.
The <xref> element may be used to reference anything that has an @id attribute. This single element takes the place of the many named types of references (such as figure references, table references, and footnote references) that are common in many journal tag sets. This attribute preserves the information from such tag sets concerning the type of element to which the cross-reference is pointing.
| Value | Meaning |
|---|---|
| aff | Affiliation. |
| app | Appendix. |
| author-notes | Author notes. |
| bibr | Bibliographic reference (typically to a <ref> element, but it may point to a <element-citation> or <mixed-citation> if there are multiple citations inside the <ref> element). |
| boxed-text | Textbox or sidebar. |
| chem | Chemical structure (to a <chem-struct> or <chem-struct-wrap> element). |
| contrib | Contributor. |
| corresp | Corresponding author. |
| disp-formula | Display formula. |
| fig | Figure or group of figures (to a <fig> or <fig-group> element). |
| fn | Footnote. |
| kwd | Keyword. |
| list | List or list item (to a <list> or <list-item> element; also, possibly to a <def-list> or <def-item> element). |
| other | None of the items listed. |
| plate | Plate. |
| scheme | Scheme. |
| sec | Section. |
| statement | Statement. |
| supplementary-material | Supplementary information. |
| table | Table or group of tables (to a <table-wrap> or <table-wrap-group> element). |
| table-fn | Table footnote. |
| Restriction: | |