To start a conversation on the initiator's side, the initiator's back‐end system invokes the pub.estd.chem:processDocument service. To start a conversation on the fulfiller's side, a service invoked by the initiator's Send to Seller step sends the PO (in Chem eStandards format) to the pub.estd.chem:receive service. Both the pub.estd.chem:processDocument and pub.estd.chem:receive services invoke wm.tn.doc:recognize to recognize document by matching it against the TN XML document types. On each side, a BizDocEnvelope is created. Both the pub.estd.chem:processDocument and pub.estd.chem:receive services send the BizDocEnvelope to the Process Engine.

On each side, the Process Engine checks to see if a ConversationID exists for the conversation. If no ConversationID exists, the webMethods Chem eStandards Module creates a ConversationID. Then the Process Engine creates a new instance of the process model and assigns the ConversationID to the process model. The Process Engine executes the conversation based on the steps defined in the process model.