Is DTD extensible?

Related questions

1. What is the difference between DTD and XML Schema?
2. What is DTD and its types?
3. What is difference between DTD and schema?
4. When should I expect contractions?
5. What is the difference between XML Schema and XML DTD?
6. What is DTD explain with example?
7. What causes Labour to start?
8. What is DTD what is its importance with respect to an XML document?
9. What does DTD stand for in Kra?
10. What is internal DTD?

Tags

1. #document
2. #initial
3. #markup
4. #schema
5. #languages
6. #other
7. #format
8. #definition
9. #widely
10. #language
11. #simple
12. #exist
13. #relax
14. #including
15. #derived
16. #extensible
17. #flexible