* Infrastructure (schema support - DTD, Schema, RelaxNG; transformation - XSLT) * No obvious document format (What encoding are the strings? How to escape characters? * Only used to describe predefined object types (boolean, strings, arrays, dictionaries * Hard to ensure the integrity of the data without interpreting the data from the interpreter itself (no external validation)

You know this can be done on top when you have demand for this? I prefer a non-bloated protocol format over XML anytime. How often does the DTD not matter at all ? How often is the encoding fixed by convention ? ...

I use schemas (in the form of RelaxNG most of the time) almost every time I deal with XML. Together with schematron you can make very complex lint-like scripts to verify your data. Actually I program in XML with a self created programming language (formulated in XML). This together with RelaxNG and a good XML makes it fun writing XML and absolutely (syntax-)error free.

I could just as similarly ask why the author even mentions XML ?