The basis idea is that if you have an XProc step declared as

1 |<p:declare-step type="test:example" xmlns:test="http://test">
  |  <p:input port="source" content-types="xml" sequence="true" primary="true"/>
  |  <p:input port="second" content-types="json" sequence="false" />
  |  <p:option name="option1" as="xs:string*" />
5 |  <p:option name="option2" as="xs:boolean" />
  |  <p:output port="result" />
  |</p:declare-step>

it can be called as an XPath function like

1 |test:example(
  |   ($doc1, $doc2),       (:value sequence for port 'source':)
  |   map{'key' : 'value'}, (:single value for port 'second':)
  |   map{xs:QName('option1') : ('String-1', 'String-2'),
5 |       xs:QName('option2') : true()})

Every input port in the XProc step creates one argument of the XPath function in numeric order. If the step has options, the last function argument is a map where the keys are xs:QNames representing the option name. The function's result is always a map with xs:NCNames as keys representing the names of the step's output ports. The function's name is equal to the step's type-declaration (not it's name!). The correlation between the input port's declaration and the function signature is as follows:

Which steps are visible as functions depends on the pipeline: If the pipeline has a p:declare-step root element, the declared step is available as a function provided it has a type attribute. If the root element is a p:library all steps declared in this library having a type attribute are available via function call. Also all steps from imports directly to that library are available. The visibility attribute currently is ignored (for now) so you can call steps marked as “private” as functions too.

To use XProc steps from a pipeline or library in the XPath context of XSLT or XQuery, you have to use a Saxon startup hook provided by class com.xml_project.morganaxproc3.saxon13connector.RegisterXProcStepsAsFunctions with -init on the command line interface. You need to have MorganaXProc-IIIee.jar or MorganaXProc-IIIhe.jar on the classpath starting Saxon. Additionally all relevant jar-files from MorganaXProc's library folder have to be on the classpath. (see details in Configuration). At least you need to have MorganaXProc-IIIee_lib/Saxon13Connector.jar on your classpath to make the function call work.

Additionally you have to use the following Java properties to make it work:

The following example might help to clarify the necessary configuration (for Linux/MacOS). An adaption for Windows is pretty straight forward:

   |MORGANA_HOME=$(dirname $CURRENT_SCRIPT)./vanilla-III/MorganaXProc-IIIee-1.8.11
   |MORGANA_PATH=$MORGANA_HOME/MorganaXProc-IIIee.jar
   |MORGANA_LIB=$MORGANA_HOME/MorganaXProc-IIIee_lib/*
   | 
   |SAXON_PATH=/users/berndzen/documents/software/JavaKlassen/SaxonHE13-0J/saxon-he-13.0.jar
   | 
   |CLASSPATH=$SAXON_PATH:$MORGANA_PATH:$MORGANA_LIB:$MORGANA_HOME/MorganaXProc-IIIee_lib/Saxon13Connector.jar
   | 
   |java -Dcom.xml_project.morganaxproc.config=morgana-config.xml \ 
   |  -Dcom.xml_project.morganaxproc.pipeline=pipeline.xpl \
   |  -Dcom.xml_project.morganaxproc.statics=statics-defs.xml \ 
   |  -cp $CLASSPATH net.sf.saxon.Transform -s:source.xml -xsl:stylesheet.xsl \ 
   |  -init:com.xml_project.morganaxproc3.saxon13connector.RegisterXProcStepsAsFunctions 

In stylesheet stylesheet.xsl all the steps declared in pipeline.xpl are available as functions in all XPath expressions.