This glossary gathers together some of the more common technical terms used in this book. Most of these terms are defined in the XSLT or XPath specifications, but some of them are borrowed from XML or other standards in the XML family, and one or two have been invented for the purposes of this book. So for each definition, I also tell you where the term comes from.
The definitions in all cases are my own; in some cases, the original specifications have a much more formal definition, but in other cases they are surprisingly vague.
Where a definition contains references to other terms defined in the glossary, these terms are written in italics.
The ancestor axis selects the parent of the context node, its parent, and so on, up to and including the root node. This axis is a reverse axis.
The ancestor-or-self axis selects the context node followed by all the nodes on the ancestor axis. This axis is a reverse axis.
The arity of a function is the number of parameters defined in the function signature; for example, the arity of the function
true() is zero, while the two versions of the
contains() function have arity two and three, respectively.
An atomic value is an item such as an integer, a string, a date, or a boolean. Specifically, it is an instance of the class
xs:anyAtomicType, which includes all simple types (as defined in XML Schema) that are not list types or union types.