The xslt mediator applies the specified XSLT transformation to the selected element of the current message payload. If the source element is not specified, it defaults to the first child of the soap body. Optionally parameters (XSLT) could be passed into the transformations through the 'property' field. The 'feature' field defines any features which should be explicitly set to the TransformerFactory. The feature 'http://ws.apache.org/ns/synapse/transform/feature/dom' turns on DOM based transformations instead of serializing elements into Byte streams and/or temporary files. Though this would be better in performance than using byte streams, sometimes it may not work for all transformations.
XSLT Mediator
Manage the properties which would be referred from the xslt in transformation (using get-property(prop-name) xpath extension function).
XSLT Mediator - Add Properties
Specify the features to be enabled in the XSLT transformation. Read the introduction paragraph of this guide for an example feature.
XSLT Mediator - Add Features