I have shared my org's salesforce partner wsdl to an external system. I send a request to them using SOAP callout and in the request I send the ID of a parent Sobject.
Now the external system makes an inbound call to update some records in Salesforce using partner WSDL. They only have the parent ID with them using which they will call the update service. Is it possible for the external system to use this parent ID and update the child records of the parent ? If Not is there a way to do this?