| Validity |
|
|
|
|
|
|
|
|
|
|
|
|
| • | A well-formed
document has a tree structure and |
||||||||||
| obeys all the XML
rules. |
|||||||||||
| • | A particular
application may add more rules in |
||||||||||
| either a DTD
(document type definition) or in a |
|||||||||||
| schema. |
|||||||||||
| • | Many specialized
DTDs and schemas have |
||||||||||
| been created to
describe particular areas. |
|||||||||||
| • | These range from
disseminating news bulletins |
||||||||||
| (RSS) to chemical
formulas. |
|||||||||||
| • | DTDs were
developed first, so they are not as |
||||||||||
| comprehensive as
schema. |
|||||||||||