Out of many candidates for XML schema language W3C XML Schema is the only one to introduce PSVI or post-schema validation infoset. PSVI is returned by schema processor analogous to how Infoset is returned by parsers. Infoset is "an abstract data set ... that provides ... definitions to refer to the information in a well-formed XML document"; PSVI works for validated and well-formed XML document. PSVI provides not only information on validation of an XML document but also type information on elements and attributes as well as their default values. And yet even W3C working group does not have use cases!

PSVI inevitably raises many questions:

• Will majority of XML users use it? If so how?
• What is the cost of producing PSVI? Who pays for it?
• Doesn't it change XML as we know it to something different?

Especially PSVI's type system already generates strong objections and dissents like "One typesys to rule them, and in the darkness bind them."

PSVI will affect the future of XML profoundly, or will it?