.NET: Difference between SGML and XML

Below are the differences between the XML and SGML:

1. XML is a subset of SGML  or we can say a simplified version of SGML.
2. XML is simpler as compared to SGML.
3. XML documents should be readable with SGML parsers while some SGML might produce errors in    
    XML parsers.
4. A list of SGML declarations have been removed in XML.
5. Some constructs that are allowed in SGML are no longer permitted in XML.
6. Some SGML entities are no longer allowed in XML.
7. Some comment practices in SGML have also been disallowed in XML.