XML Schema

XML Schema, published as a W3C Recommendation in May 2001, is one of several XML schema. It was the first separate schema language for XML to achieve Recommendation status by the W3C.

Since other XML schema languages such as RELAX NG now exist, it is important to cite this language as either XML Schema or W3C XML Schema, always with the word Schema capitalized. An XML Schema instance is an XML Schema Definition (XSD) and typically has the filename extension .xsd . The language itself is sometimes informally referenced as XSD, even though WXS (W3C XML Schema) is the more appropriate Acronym and initialism.

In its appendix of references, XML Schema acknowledges the influence of and Commerce One, respectively, have both announced that they would support XML Schema for their new developments, so W3C XML Schema should become the only surviving member of this family.

After XML Schema-based validation, it is possible to express an XML document s structure and content in terms of the data model that was implicit during validation. The XML Schema data model includes:

the vocabulary (Element/Attribute names)

the content model (Relationships/Structure)

and data types.

This collection of information is called the PSVI. The PSVI gives a valid XML document its type and facilitates treating the document as an object, using object-oriented programming (OOP) paradigms. This particular OOP approach to XML data access was primarily advocated by Microsoft, a major contributor to the development of XML Schema. Converting an XML document to a Datatype-aware object can be beneficial in some parts of computer software design, but critics contend that it also undermines openness, a key feature of XML, and that it is biased toward compatibility with the datatypes native to Microsoft s favored programming languages. [http://www.biglist.com/lists/xsl-list/archives/200302/msg00821.html]

= Example =

An example of a very simple Schema to describe a country is given below.

An example of an XML document that conforms to this schema is given below.

France 59.7

=External links=

*[http://www.zvon.org/xxl/xmlSchema2001Reference/Output/index.html Zvon XML Schema Reference] *[http://www.w3.org/XML/Schema World Wide Web Consortium XML Schema] *[http://xmlzoo.net/xsd/ XSD tutorial] from XMLzoo *http://www.xml.com/pub/a/2001/12/12/schemacompare.html *[http://www.xmlpatterns.com XMLPatterns.com - Design patterns for developing XML Schema documents] *[http://www.w3schools.com/schema/default.asp W3Schools XML Schema Tutorial] *[http://www.stylusstudio.com/xml_schema_tutorial.html XML Schema Development Tutorial] from Stylus Studio - NB this is more of a tutorial in their own software than in the principles of XML Schema