Pass object to XML-to-Domain mapping

I'm using a webservice to retrieve a file. I use several (string) arguments of a certain object as an input for the webservice. The object is associated to a FileDocument object. When the file is returned by the webservice, I want to store the file in the FileDocument object that is associated to the object that contains the input parameters for the webservice. I'm not sure how to do this, because the XML-to-Domain mapping normally creates a new 'unassociated' object. I would like to pass a certain FileDocument object to the XML-to-Domain mapping, so the file is stored in the passed FileDocument object, but don't know how to do this. Thanks in advance!
1 answers

In 3.1.1 (and probably in 2.5) you can set a property on the domain-2-xml mapping to accept parameters.

And the result of the web service call can use a microflow to determine an object, so when having 2 system-filedocuments in your mapping that are related and inputting the object it needs to relate to you can write a small microflow that returns this inputted object to the result message to link to it.

This must sound vague... if you have questions let me know.