If XML is just a subset of SGML, can I use....

<script type="text/javascript" src="http://pagead2.googlesyndication.com/pagead/show_ads.js"> </script> If XML is just a subset of SGML, can I use XML files directly with existing SGML tools? Yes, provided you use up-to-date SGML software which knows about the WebSGML Adaptations to ISO 8879 (the features needed to support XML, such as the variant form for EMPTY elements; some aspects of the SGML Declaration such as NAMECASE GENERAL NO; multiple attribute token list declarations, etc). An alternative is to use an SGML DTD to let you create a fully-normalised SGML file, but one which does not use empty elements; and then remove the DocType Declaration so it becomes a well-formed DTDless XML file. Most SGML tools now handle XML files well, and provide an option switch between the two standards. (see the pointers in the question on software).