Unique identifier for a table so that its content may be cross-referenced
The ID and IDREF attribute values form a primitive reference mechanism for XML. When an @id attribute has been used on a <table> element, that identifier can be referenced by an IDREF-style attribute on a <xref> element, so that the full table can be pointed to. Accordingly, IDs must be unique inside their document (not just within their element type), and the XML parser enforces this.
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.)
| 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. | |