1. An SGML validation system comprising: an XML validation engine; a translator configured to convert an SGML document to a translated XML document using a p-isomorphic translation; an XML schema against which the XML validation engine validates the translated XML document, the XML schema configured such that errors detected by the validation of the translated XML document correspond to SGML errors in the SGML document; and a report generator configured to generate an error report identifying SGML errors corresponding with errors detected by the validation and linking the identified SGML errors with corresponding locations in the SGML document; wherein the XML validation engine, the translator, and the report generator are embodied as a digital processing device.
5. The SGML validation system as set forth in claim 1 , wherein the XML schema comprises: an exclusion tree schema component, an error detected by validation against the exclusion tree schema component corresponding to an occurrence in the SGML document of a sub-tree that is excluded by an SGML DTD associated with the SGML document.