Validating xml parser c

Though there are a number of schema languages available, the primary three languages are Document Type Definitions, W3C XML Schema, and RELAX NG.

Each language has its own advantages and disadvantages.

Unlike W3C XML Schema, RELAX NG was designed so that validation and augmentation (adding type information and default values) are separate.

W3C XML Schema has a formal mechanism for attaching a schema to an XML document, while RELAX NG intentionally avoids such mechanisms for security and interoperability reasons.

The W3C XML Schema language in particular can be quite verbose, while a DTD can be terse and relatively easily editable.

Likewise, WXS's formal mechanism for associating a document with a schema can pose a potential security problem.

XSD schemas are conventionally written as XML documents, so familiar editing and transformation tools can be used.

As well as validation, XSD allows XML instances to be annotated with type information (the Post-Schema-Validation Infoset (PSVI)) which is designed to make manipulation of the XML instance easier in application programs.

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DTD-validating parsers are most common, but some support XML Schema or RELAX NG as well.W3C XML Schema is complex and hard to learn, although that's partially because it tries to do more than mere validation (see PSVI).Although being written in XML is an advantage, it is also a disadvantage in some ways.For WXS validators that will follow a URI to an arbitrary online location, there is the potential for reading something malicious from the other side of the stream.W3C XML Schema does not implement most of the DTD ability to provide data elements to a document.DTDs are perhaps the most widely supported schema language for XML.Because DTDs are one of the earliest schema languages for XML, defined before XML even had namespace support, they are widely supported.RELAX NG has no ability to apply default attribute data to an element's list of attributes (i.e., changing the XML info set), while W3C XML Schema does.Again, this design is intentional and is to separate validation and augmentation.There are several different languages available for specifying an XML schema. The primary purpose of a schema language is to specify what the structure of an XML document can be.This means which elements can reside in which other elements, which attributes are and are not legal to have on a particular element, and so forth.

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