Related to the values to describe relationships between VTODO objects, the example shows 2 cases where we put to values in a single element's valule, the relationship type and a time gap: SF+10m and FS+T00.10 2 issues behind this: First it would be better to serialize the relationship type as an XML element value, and the time gap as a sub-element (or an attribute). Second, I am not sure that 10m is a valid iCal duration. This time gap shall be a valid duration.