Indicates the type of element to which a cross reference is pointing (e.g., to a figure, an author note, a bibliographic reference citation, etc.). These values may be used for type-specific processing or validation.
The <xref> element may be used to reference anything that has an Identifier 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 DTDs. This attribute preserves the information from such DTDs concerning the type of element to which the cross-reference is pointing.
| Value | Meaning |
|---|---|
| aff | Affiliation |
| app | Appendix |
| bibr | Bibliographic reference (to a <citation>, <nlm-citation>, or <ref> element) |
| boxed-text | Textbox or sidebar |
| chem | Chemical structure (to a <chem-struct> or <chem-struct-wrapper> element) |
| contrib | Contributor |
| corresp | Corresponding author |
| disp-formula | Display formula |
| fig | Figure (to a <fig> 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 (to a <table-wrap> element) |
| table-fn | Table footnote |
| Restriction: This attribute may be specified if the element is used. | |