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W3C XML Schema is complex and hard to learn, although that is 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. The W3C XML Schema language, in particular, can be quite verbose, while a DTD can be terse and relatively easily editable.
An XML Schema Definition is itself an XML document while a DTD is not. RELAX NG, which is also a part of DSDL, is an ISO international standard. [9] It is more expressive than XSD, [citation needed] while providing a simpler syntax, [citation needed] but commercial software support has been slow in coming.
When the schema is compiled into XMLBean classes (e.g., using Ant), it is very easy to create and manipulate XML data that conforms to the schema definition. The following Java code is a simple example that illustrates how an XML document can be created and validated.
XML schema based: Based on an existing XML schema, classes that correspond to the schema are generated. Class based: Based on a set of classes to be serialized, a corresponding XML schema is generated. Mapping-based: A mapping description, usually itself an XML document, describes how an existing XML schema maps to a set of classes, and vice versa.
The tool "xjc" can be used to convert XML Schema and other schema file types (as of Java 1.6, RELAX NG, XML DTD, and WSDL are supported experimentally) to class representations. [3] Classes are marked up using annotations from javax.xml.bind.annotation.* namespace, for example, @XmlRootElement and @XmlElement.
The oldest schema language for XML is the document type definition (DTD), inherited from SGML. DTDs have the following benefits: DTD support is ubiquitous due to its inclusion in the XML 1.0 standard. DTDs are terse compared to element-based schema languages and consequently present more information in a single screen.
A document type declaration, or DOCTYPE, is an instruction that associates a particular XML or SGML document (for example, a web page) with a document type definition (DTD) (for example, the formal definition of a particular version of HTML 2.0 - 4.0). [1]
This article lists the character entity references that are valid in HTML and XML documents. A character entity reference refers to the content of a named entity. An entity declaration is created in XML, SGML and HTML documents (before HTML5) by using the <!ENTITY name "value"> syntax in a Document type definition (DTD).