| string | character string |
| normalized string | line breaks are normalized |
| token | whitespace is normalized |
| NMTOKEN | should not contain whitespace (attribute only) |
| NMTOKENS | List of NMTOKENs (attribute only) |
| Name | not starting with a digit |
| NCName | cannot contain colons |
| ID | unique identification in document (attribute only) |
| IDREF | reference to ID field in document (attribute only) |
| IDREFS | list of references to ID fields in document (attribute only) |
| ENTITY | reference to entity (attribute only) |
| ENTITIES | list of references to entities (attribute only) |
| language | language codes |
