straintSpec ident=maintitle scheme=isoschematron> <constraint> <s:assert test=tei:fileDesc/tei:titleStmt/tei:title[@type='main']> a main title must be supplied </s:assert> </constraint></constraintSpec>As a further example, Schematron may be used to enforce rules applicable to a TEI document which is going to be rendered into accessible HTML, for example to check that some sort of content is