The invocation sequence of services is shown for each process or sub-process in a sequence diagram describing the interaction between the services involved. It will be an orchestration of services if there is an organization that controls its, or a choreography if it involves more than one organization in a collaborative process with pre-defined communication with other parties.This insight is provided by a sequence diagram showing all the services, or various sequence diagrams showing different subsets of services corresponding to different sub-processes in the business process.    

Example of a sequence diagram showing an interaction of services for the sub-process "Loan Authorization" from a "Grant Loan" business process of a bank: