Just what it says... a tin without breaklines is not nothing more than a delauny(sp) triangulation you give me any set of 3d points in #,y,x,z whatever and I can create a tin and contour it in minutes. However it won't necessarily be right or worth a damn . There things like scale and national mapping standards that have to be considered for a 'good' dtm
I collect my own topos with a topcon 8005 robot and Carlson survcad and can go from field data to tin and contours within 5minutes of downloading my datacollector.