Re: Calling xpa web service
Well that strange ARGUMENTS= thing originates from v8 20 years ago and Magic never really managed to document it. You can find it in some of the samples or documented (well, sort of documented) together with the command line requester (-> http://kb.magicsoftware.com/articles/bl_Reference/Command-Line-Requester-xpa-3x) . Its basically a strange "RPC style" concept invented for the first versions which has been forgotten to be replaced by something decent.
Basically you do already *have* a webservice implemented here and you could even specify an API complying with standards based on it - where the request body is application/x-www-form-urlencoded (https://swagger.io/docs/specification/describing-request-body/) . There just wont be much tools which support this, Swagger f.i. does.
When you do mean "SOAP XML with Systinet" when you refer to webservices. Thats totally legacy and you should just forget about that ;). Also better get rid of Magic broker and use Gigaspaces or different middleware. Thats recommendations based on personal experience with Magic Broker technology .