Validating and non validating parser difference
In this tip, I show you how to do that using the SAX API.Because SAX is event driven, you'll want to be notified of, and react to, any errors that occur during validation. XMLReader Factory; public class Validate XML class My Error Handler implements Error Handler as it brings things to a crashing halt when any problems arise.It does not consult the document type definition which describes the source, but carries out simple checks, such as ensuring that each tag is associated with its end tag.Apart from the built-in DTD support in parsers, lxml currently supports three schema languages: DTD, Relax NG and XML Schema.All three provide identical APIs in lxml, represented by validator classes with the obvious names.lxml also provides support for ISO-Schematron, based on the pure-XSLT skeleton implementation of Schematron: There is also basic support for The parser in lxml can do on-the-fly validation of a document against a DTD or an XML schema.
If you want to validate an XML document against a DTD that is not referenced by the document itself, you can use the keyword argument to parse from a file.In XML parsers, validation is usually turned off by default because many XML authors are not writing constraints; leaving it off helps to avoid lengthy processing in production environments.To turn on validation, you must request it explicitly.The key to giving meaning to an XML document -- and the crux of validation -- lies in the set of constraints that governs that document, and in ensuring that those constraints are followed.
As an example, the element elements are allowed (as in a lengthy novel with hundreds of pages).while DOM gave us facility of tree structure which we can obtain from an XML document after parsing it with SAX parser.