Translate definición de tipo de documento from Spanish to English

– A set of syntax rules for mark-up tags and their interpretation. Within an HTML (or XML) document, a DTD provides specific information on what tags are used in the document (and in what order those tags should appear), which tags can appear inside other ones, which tags have attributes, and so forth. Originally developed for use with Standard Generalized Markup Language (SGML), DTD defines the relationships between document elements. ¹