Book 2.1

id

Identifier

Definition

Indicates the unique identifier for an associated element, so that the element’s content may be cross-referenced. IDs must be unique inside their document (not just within their element type), and the XML parser enforces this.

Usage

The ID and IDREF attribute values constitute a primitive reference mechanism for XML. For example, when an id attribute has been used on a <glyph-data> element, that identifier can be referenced by an IDREF-style attribute on a <glyph-ref> element, so that the full glyph data can be pointed to and need not be repeated every time the character is used.

Remarks

An identifier string is typically 1-32 characters in length and must start with a letter of the alphabet. (It is an XML rule that identifiers may not start with a digit.)

Authoring Note: At present, not all elements with a id attribute are actually of type ID and can be cross-referenced. To ensure backwards compatibility with prior versions of other DTDs created using the base DTD Suite (i.e., the Journal Publishing DTD and Journal Archiving DTD, versions 1.0, 1.1), the following elements cannot be referenced using the ID/IDREF mechanism:

These elements use a CDATA (data character) attribute type, which does not possess the same cross-reference capability as an ID attribute type found on such elements as <fn>.

Attribute Values

In Elements

<def-list> Definition List; <list> List; <list-item> List Item; <tex-math> Tex Math Equation
Value Meaning
Text, numbers, or special characters Unique identifier for the element within its document. Parsers cannot check uniqueness or matching.
Restriction: This attribute may be specified if the element is used.

In Elements

<overline-start> Overline Start
<underline-start> Underline Start
Value Meaning
An XML identifier (ID) A unique identifier for the element. An XML parser can verify that an IDREF-style attribute pointing to one of these is pointing to a valid ID.
Restriction: This attribute must be specified if the element is used.

In Elements

<abbrev> Abbreviation or Acronym; <ack> Acknowledgments; <address> Address/Contact Information; <aff> Affiliation; <alt-text> Alternate Title Text (For a Figure, Etc.); <app> Appendix; <array> Array (Simple Tabular Array); <author-notes> Author Note Group; <bio> Biography; <book-part> Book Part; <boxed-text> Boxed Text; <caption> Caption of a Figure, Table, Etc.; <chem-struct> Chemical Structure (Display); <chem-struct-wrapper> Chemical Structure Wrapper; <citation> Citation; <col> Table Column (XHTML table model); <colgroup> Table Column Group (XHTML table model); <collab> Collaborative (Group) Author; <collection> Collection; <contrib> Contributor; <corresp> Correspondence Information; <def> Definition List: Definition; <def-item> Definition List: Definition Item; <disp-formula> Formula, Display; <disp-quote> Quote, Displayed; <ext-link> External Link; <fig> Figure; <fig-group> Figure Group; <fn> Footnote; <glossary> Glossary Elements List; <glyph-data> Glyph Data for a Private Character; <graphic> Graphic; <inline-formula> Formula, Inline; <inline-graphic> Graphic, Inline; <inline-supplementary-material> Inline Supplementary Material; <institution> Institution Name: in an Address; <kwd> Keyword; <kwd-group> Keyword Group; <long-desc> Long Description; <map-group> Image Map; <media> Media Object; <mml:math> Math (MathML 2.0 DTD); <named-content> Named Special (Subject) Content; <note> Note in a Reference List; <notes> Notes; <p> Paragraph; <preformat> Preformatted Text; <ref> Reference Item; <related-article> Related Article Information; <sec> Section; <speech> Speech; <statement> Statement, Formal; <supplementary-material> Supplementary Material; <table> Table (XHTML table model); <table-wrap> Table Wrapper; <table-wrap-group> Table Wrapper Group; <target> Target of an Internal Link; <tbody> Table Body (XHTML table model); <td> Table Data Cell (XHTML table model); <term> Definition List: Term; <tfoot> Table Footer (XHTML table model); <th> Table Header Cell (XHTML table model); <thead> Table Header (XHTML table model); <tr> Table Row (XHTML table model); <verse-group> Verse Form for Poetry; <xref> X(cross) Reference
Value Meaning
An XML identifier (ID) A unique identifier for the element. An XML parser can verify that an IDREF-style attribute pointing to one of these is pointing to a valid ID.
Restriction: This attribute may be specified if the element is used.

Book 2.1

Version of 20050930