RELAX Core and TREX are schema languages for XML. RELAX Core was designed in Japan and has recently been approved as an ISO Technical Report (ISO TR 22250-1); TREX was designed by James Clark. RELAX Core and TREX are similar; they are based on tree automata and do not change information sets. On the other hand, there are some significant differences: attributes, unordered content models, namespeces, wild cards, the syntax, and the underlying implementation techniques. At OASIS it wazs decided to unify these two languages and the new language is called RELAX NG. This talk shows how differences between RELAX Core and TREX are resolved in RELAX NG.