This package is Saxon's implementation of the JAXP API designed for executing XPath 1.0 expressions directly from a Java application. Saxon extends the interface to handle XPath 2.0, though if the application makes extensive use of XPath 2.0 features, then the s9api interface offers a better fit to the XPath 2.0 data model. The API can be used either in a free-standing Java application (that is, where there is no XSLT stylesheet), or it can be used from within Java extension functions called from XPath expressions within a stylesheet.

The API itself is defined by JAXP 1.3, in interfaces such as `javax.xml.xpath.XPath`.< These interfaces are included in Java Standard Edition from JDK 1.5 onwards.

The interfaces provided by Saxon extend the JAXP 1.3 interfaces in various ways. There are three reasons for this:

- Saxon supports XPath 2.0 rather than 1.0

- The package retains support for some interfaces that were provided before JAXP 1.3 was released. (Most of these extensions have been deprecated for several releases, and most removed in Saxon 9.6).

- There are methods that allow an escape into Saxon's more low-level APIs, needed by anyone doing serious software integration.

For most applications the preferred interface is the s9api {@link net.sf.saxon.s9api.XPathCompiler}