Identifies which version of the Tag Set, named in the DOCTYPE declaration, was used to make the document under consideration, which therefore should be used to validate this document.
Best Practice: This is a “fixed” attribute (meaning that the value is set via a parameter entity in the DTD; thus, an author or editor cannot change it) that should change every time the Tag Set changes versions or revisions.
| Value | Meaning |
|---|---|
| 0.6 | The document was tagged to version 0.6 of the DTD |
| Restriction: This attribute value may not be changed. | |