module xpath-1.1 {
    namespace "urn:xpath-1.1";
    prefix xp;

    container top {
        leaf identref {
            type mdentityref {
                base:iwo;
                     pattern '[A-Z]+';
                pattern '[A-Z]+';
                   pattern '[A-Z]+';
                    pattern '[A-Z]+';
                pattern '[./key2, 2, 3), 'a') and not(starts-with(./key2, 'a')))";
}