# What is Saxon?

The Saxon package is a collection of tools for processing XML documents. The main components are:

- An XSLT 2.0 processor, which can be used from the command line, or invoked from an application, using a supplied API. This can also be used to run XSLT 1.0 stylesheets.

- An XPath 2.0 processor accessible to applications via a supplied API.

- An XQuery 1.0 processor that can be used from the command line, or invoked from an application by use of a supplied API.

- An XML Schema 1.0 processor. This can be used on its own to validate a schema for correctness, or to validate a source document against the definitions in a schema. It is also used to support the schema-aware functionality of the XSLT and XQuery processors. Like the other tools, it can be run from the command line, or invoked from an application.

- As well as providing full implementations of the stable specifications listed above, Saxon also has a track record of early implementation of forthcoming standards. Saxon 9.3 offers a complete implementation of XQuery Updates and a near-complete implementation of XML Schema 1.1, both of which are in the final stages of standardization. It also implements many features from the forthcoming XSLT 3.0, XQuery 3.0, and XPath 3.0 working drafts which are still at an earlier stage of development.

- On the Java platform, when using XSLT, XPath, or XML schema validation, Saxon offers a choice of APIs. If you need portability across different vendor's tools, you can use the JAXP API for XSLT, XPath, and XML Schema processing, and the XQJ interface for XQuery. On the other hand, if you want a more integrated and complete API offering access to all Saxon's facilities, the s9api interface is recommended. You can also dive down deeper into the Saxon internals if you need to: there has been no particular attempt to make interfaces private, and all public interfaces are documented in the JavaDoc. Clearly, the deeper you go, the greater the risk of interfaces changing in future releases.

- On the .NET platform, Saxon offers an API that enables close integration with other services available from .NET, notably the XML-related classes in the `System.Xml` namespace. It isn't possible to use Saxon as a transparent plug-in replacement for the `System.Xml.Xsl` processor, because the API for the Microsoft engine using concrete classes rather than abstract interfaces. However, it is possible to use it as a functional replacement with minor changes to your application code.

Full details of Saxon's conformance to the specifications are provided in the Conformance section.

In addition, Saxon provides an extensive library of extensions, all implemented in conformance with the XSLT and XQuery Recommendations to ensure that portable stylesheets and queries can be written. These include the EXSLT extension libraries common, sets, math, and dates-and-times. Many of these extensions were pioneered in Saxon and have since become available in other products.

These extension functions are in general accessible from XQuery and XPath as well as XSLT, except where they depend on stylesheet information. Many extensions are available in Saxon-PE only, and some only in Saxon-EE.

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