Hei Dawn.
As it relates to DFD template style, the spreadsheet that I shared uses a Threat Analysis Methodology that I am comfortable with. It is based on the Microsoft TAM but also
consistent with the ISF approach.
Here is an example with the various charting symbols for a diagraming data flow in a use case. The template I included in the spreadsheet includes another symbol for an interface/connector
because in web service design these are very much used constructs and often under control of either a third-party or 1st party.
Frank/