ILIAS Developers: SOAP Plugin

Hi,

I'm trying to create a SOAP plugin for the SOAP plugin slot and am running into issues with the input params.  I've setup the soap example method "getObjectTitleByRef" from this page https://docu.ilias.de/goto_docu_wiki_wpage_4573_1357.html and can get that working.  However, if I add an additional parameter, like a usr_id,  and then pass it in my SOAP client I get a SoapFault exception saying "Request is missing at least one of the following parameters: sid, ref_id, usr_id".  Are there any specific steps when adding new input params?

Thanks,

Chris