1. A method for parsing a document, the document being in an Extensible Markup Language (XML) format, the method comprising: identifying data via the XML format; defining a tag set including a plurality of tags; defining a tokenizer that produces one token at a time; parsing the XML document via a parser; validating the XML document via a validation engine, the validation engine driving the tokenizer, and the validating being an integral part of the parsing; and permitting the validation engine to be written in a recursive-descent code-driven manner.