The relationships linking the realizations of the ITRS is of utmost importance. They are based on transformation parameters (called Helmert parameters). They can be used to compare data or results expressed in two different ITRS realizations.
Transformation Parameters between ITRF2014 and previous solutions
Transformation Parameters between ITRF2008 and previous solutions
Transformation Parameters between ITRF2005 and ITRF2000
Transformation Parameters between ITRF2000 and previous solutions
ITRS and WGS84