What SAXON extension (?) enables my XSLT program to get information about XSD elements?

Hi Folks,

I want to write an XSLT program that traverses the leaf elements of XML instance documents. As the XSLT program visits each element, the program goes to the element declaration in the corresponding XML Schema and collects schema-information about the element, such as minOccurs, maxOccurs, type, default, fixed, and facets (if applicable). I believe that SAXON has an extension (?) which provides access to all sorts of valuable information about the XML Schema. I believe that I used the extension (?) long ago, but I've forgotten what its name is. Would you point me to the thing that I am looking for, please?

/Roger