An instance document is valid if and only if it conforms to the rules of the XML schema. An XML schema document contains rules describing the structure of an input XML document, called an instance document. An XML schema is an XML document written in the XML Schema language. The XML Schema language, also known as XML Schema Definition, was created by the W3C to use XML syntax to describe the content and the structure of XML documents.
Most processors can enable or disable validation mode, but they must still process entity definitions and other constructs of DTDs.Ĭoncepts involving validation using XML schemas are introduced. Depending on its implementation, a validating parser may:Įither stop processing when it encounters an error, or continue.Įither report warnings and errors as they occur or in summary form at the end of processing.
Using XDK, you can write an application that includes a validating XML parser that is, a program that parses and validates XML documents against a DTD. Thus, applications that handle XML documents can assume that the data matches the definition. Validation is the process by which you verify an XML document against its associated DTD, ensuring that the structure, use of elements, and use of attributes are consistent with the definitions in the DTD. You can declare a DTD in an XML document itself or in a separate file from the XML document. DTDs can also specify whether attributes are optional or mandatory.Įntities that are legal in your XML documents.Īn XML DTD is not itself written in XML, but is a context-independent grammar for defining the structure of an XML document. DTDs can define whether a subelement is optional or mandatory and whether it can occur only once or multiple times.Īttributes of XML elements. The content model of an XML element, that is, whether the element contains only data or has a set of subelements that defines its structure. Which elements can be in your XML documents. XML DTDs are a subset of those available in SGML and provide a mechanism for declaring constraints on XML markup. Document type definition (DTDs) were originally developed for SGML.
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