Tony,
The process flow diagram need not show the data object (inputs or outputs). However, if you consult the BPMN 1-1 Specification at the OMG site, you'll note that the Process Attributes expected include InputSets and OutputSets. Now, most people think that by drawing the diagrams without data objects (these are optional) that they've captured the process. Well these people need to be punished, let them them listen to Celine Dion songs for 10 hours staight.
Download the BPMN 1.1 spec and go to appendix B, there you'll find the description of the InputSET and OutputSET. Here is an extract from p 274.
Zero or more ArtifactInputs MAY be defined for each InputSet. For the
combination of ArtifactInputs and PropertyInputs, there MUST be at least one
item defined for the InputSet. An ArtifactInput is an Artifact, usually a Data
Object. Note that the Artifacts MAY also be displayed on the diagram and MAY
be connected to the activity through an Association--however, it is not required
for them to be displayed. Further details about the definition of an ArtifactInput
can be found in Section B.11.1, “ArtifactInput,” on page 268.
Enterprise Architect from SPARX implement these in the attribute tab. BIZAGI allows you to define these. In my opinion most PROCESSes must have at least ONE input and/or OUTPUT.
Now it can be very frustrating when you ask SMEs and/or Consultants (mostly the latter) "What are the inputs to this process?". And you get blank stares!
The candle is still burning!
All the best.
warm regards,
K