Validating xml parser requires
All XML documents must be well-formed, but it is not required that a document be valid unless the XML parser is "validating", in which case the document is also checked for conformance with its associated schema.DTD-validating parsers are most common, but some support XML Schema or RELAX NG as well.An XML schema is a description of a type of XML document, typically expressed in terms of constraints on the structure and content of documents of that type, above and beyond the basic syntactical constraints imposed by XML itself.These constraints are generally expressed using some combination of grammatical rules governing the order of elements, Boolean predicates that the content must satisfy, data types governing the content of elements and attributes, and more specialized rules such as uniqueness and referential integrity constraints.It is a product of the W3C XML Activity, details of which can be found at The English version of this specification is the only normative version. A list of current W3C Recommendations and other technical documents can be found at
This document has been reviewed by W3C Members and other interested parties and has been endorsed by the Director as a W3C Recommendation.
A date like: "" will, in some countries, be interpreted as 3. Think of the following situation: you order 5 gross of laser printers, instead of 5 laser printers.
With XML Schemas, most of these errors can be caught by your validating software.
There are languages developed specifically to express XML schemas.
The Document Type Definition (DTD) language, which is native to the XML specification, is a schema language that is of relatively limited capability, but that also has other uses in XML aside from the expression of schemas.
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Then, we’ll spend some time starting the project we’ll develop through the course of this book: building an XML-powered content management system.