avatech-tier Schema for an AVATecH tier file where each item describes a timespan, with start time and end time. Item times have to be in ascending order and the timespans must not overlap. They can, however, be back to back. Content can be free text, numerical values, text using a controlled vocabulary or similar. Of course all spans must provide values (v) for all columns and the values must be given in the same order as specified in the columns header attribute. production AVATecH hdl:1839/00-SCHM-0000-0000-0013-6 avatech-tier.xsd