PlanetPress Suite offers a SOAP server API Reference allowing jobs to be submitted from third party application using the SOAP protocol. Remember that SOAP stands for Simple Object Access Protocol.
While there are multiple possibilities for solutions using a SOAP server implementation, the SOAP Server API Reference is specifically for submitting jobs from a SOAP client. It implements five methods that will allow SOAP clients to submit jobs and get information from PlanetPress Workflow executing them. Note that PlanetPress Workflow already come with a SOAP client plugin, which can be used as an input, action or output; this task was renamed SOAP Legacy Client.
Since the SOAP Server API Reference is primarily targeted at programmers or systems engineers, it is rather technical.