2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/30451XML documents are described by a document type definition (DTD). An XML-grammar is a formal grammar that captures the syntactic features of a DTD. We investigate properties of this family of grammars. We show that every XML-language basically has a unique XML-grammar. We give two characterizations of languages generated by XML-grammars, one is set-theoretic, the other is by a kind of saturation property. We investigate decidability problems and prove that some properties that are undecidable for general context-free languages become decidable for XML-languages. We also characterize those XML-grammars that generate regular XML-languages.24 pagesDiscrete MathematicsComputation and LanguageF.4.2;F.4.3;D.3.1text