I think when arguing about XML, many people forget its relationship to SGML. Many of the drawbacks in XML are design decisions made in order to maintain backwar

I think when arguing about XML, many people forget its relationship to SGML. Many of the drawbacks in XML are design decisions made in order to maintain backwards compatibility with SGML tools that were in use when XML was devised. In order to simplify parsing (and in order to enable parsing a well formed document without knowing its DTD), XML threw out much of the syntactic sugar that SGML had to offer such as implicitly closed tags. I.e. Many people think that <tr><td>foo<td>bar... is invalid HTML because of missing </td>. In fact, it is perfectly valid because the HTML (SGML-)DTD specifies that a <td>-tag implicitly closes a preceding <td>. Most think it's a browser-hack. It is not. What both XML (and SGML) add over S-EXPR is support for expressing grammers, a well-defined validation mechanism and quite good support for coping with different character encoding.