A need has been identified for a function available-system-properties() to list the property names recognized by the implementation, and the WG agreed in principle to add such a function. Here is the first draft of the specification:

<fos:function name="available-system-properties">
      <fos:signatures>
         <fos:proto name="available-system-properties" return-type="xs:QName*"/>
      </fos:signatures>
      <fos:properties>
         <fos:property>deterministic</fos:property>
         <fos:property>context-independent</fos:property>
         <fos:property>focus-independent</fos:property>
      </fos:properties>
      <fos:summary>
         <p>Returns a list of system property names that are suitable for passing to
            the <function>system-property</function> function, as a (possibly empty) sequence of QNames.</p>
      </fos:summary>
      <fos:rules>
         <p>The function returns a sequence of QNames, being the names of the system properties
            recognized by the processor, in some <termref def="implementation-dependent"
               >implementation-dependent</termref> order.</p>
         <p>The function is <termref def="dt-deterministic">deterministic</termref>: that is, the
            set of available system properties does not vary during the course of a transformation.</p>
      </fos:rules>
      <fos:notes>
         <p>The function returns a list of QNames, containing no duplicates.</p>
         <p>It is intended that the QNames in this list should be suitable for passing to
            <function>system-property</function>.</p>
         
      </fos:notes>
   </fos:function>