The data sheet document is specific to a tag and must therefore be related to that tag by reusing an existing relationship between the document and your document or by creating a new relationship.
The relationship definition name must be stamped on the property SPFRelToDatasheetObj on the interface ISPFDatasheetDocumentRevision. The relationship definition is automatically added if you use the method based on the client API called CreatedClassObjAndRelForDatasheet. The value of argument 4 is stamped on the property.
The relationship definition is prefixed with +/- to indicate the direction.
This property is used when navigating to the tag to generate the data sheet to be stored as a snapshot.