I think everybody should have a greatWonderbra. There's so many ways to enhance them, everybody does it.
Truly ambitious programmers are never satisfied with what they are given and are obsessively driven to enhance what they have. I say "ambitious" rather than "great" because greatness, in my opinion, comes from knowing when it is wiser to work within the system versus when it is best to extend the system. Nevertheless, this chapter is dedicated to extending the system both from the perspective of XSLT needing functionality best implemented in another language and from the perspective of other languages needing XSLT.
Extending XSLT is, by definition, a facility on the fringes of the specification. Extensions decrease the portability of an XSLT stylesheet. This is definitely a hazard when you use extensions provided natively by your XSLT processor or when implementing your own extension. It is true even if you implement your extensions in a highly portable language like Java. The most obvious reason is that some XSLT processors are not written in Java and are thus unlikely ever to support Java-based extensions. However, even if you only want your extensions to work in Java-based XSLT processors, you might still run into trouble because the extension mechanism of XSLT was not fully standardized in Version 1.0. This state of affairs improved in Version 1.1, but 1.1 is no longer an official XSLT release and many processors ...