OLE DB Property Sets and Property Groups

Hi All,

I am writing OLE DB provider for our database engine. I am new to the OLE DB. Currently I am working on framework to support OLE DB properties.

1. The property set is a set of all the prperties that share the same GUID.
2. The Property Group is a set of all the properties that apply to a particular object (or an operation that apply to a particular object).

Given these definitions I am a little confused with the statement -- "Property sets and Property groups can overlap."

beacuse in the 'Propety Set' section of "Appendix C: OLE DB Properties" of the "OLE DB Programmer's Reference" I do not see any such overlapping as there is one to one mapping between Property set GUID and the Property group description. Also, in the "Properties by Property Groups" section there is a single Property set mentioned for each Property Group.

Where does this overlapping apply? If there is no overlapping between sets and groups why there are two sets defined? Can I simply consider Property Set and Property Group same?

Thanks,
Vivek.