Fixed typographical errors pointed out by Bill Cleveland.

Added fileVersion element to fileHeader element, so each version of a particular DAVEfunc model can be uniquely identified. Format of the version identifier is undefined.

Added an email attribute to the author element. The Extensible Name Service (xns) standard does not appear to be catching on as rapidly as hoped, so a static e-mail link will have to do for now, at least until the replacement XRI technology is more widely adopted.

Added a mandatory varID attribute to both independentVarPts and dependentVarPts so these can be associated with an input and output signal name (variableDef), respectively.

Added an optional extraDocRef element to the modificationRecord element so more than one document can be associated with each modification event. If only one document needs to be referenced, use of the optional refID in the modificationRecord itself will suffice.