Typing in Transformations

Of all the new features in XSLT 2.0, the ones that have caused the most contention — and worry — amongst existing XSLT authors are those involving typing: strong typing, static typing, and validation against schemas. These features have been introduced due to two general requirements: the requirement to align with W3C XML Schema, which entails using XML Schema's type system and validation methods; and the requirement to support analysis of queries prior to their execution and warn authors of potential problems with them. When XSLT authors express their concern about these changes, they are generally assured that, at the end of the day, if they don't want to use the new type-related features that XPath 2.0 brings, they can always ignore them by using processors that are not schema aware and do not carry out static type checking. In this paper, I'll look at the extent to which this assurance is true: to what extent is it possible to ignore the new typing features in XPath 2.0? If they can't be ignored, what are the kinds of changes that XSLT authors will have to get used to? And most importantly, do these changes offer users any real benefits?