Discover the flexibility of Schematron abstract patterns
If you have the basics of an XML format in mind, but know that you will not be able to get everyone at the table to agree to every detail of the schema, consider Schematron abstract patterns. Schematron is probably the most powerful XML schema language available (and it can be much more than just a schema language). Its advanced features, especially abstract patterns, allow for schemata that you can quickly adapt to multiple variants of XML formats. This opens up extraordinary possibilities for XML schema, including the abilities to restrict XML formats and to make them generic and adaptable as well.