XSD

XML Schema Definition is a schema language that allow users to define XML structures. It has become a W3C recommendation.

Referencing a XML Schema

When we have an XML document whose structure conforms to a given structure, we may want to reference to the XSD document where that structure is located. This is done with the schemaLocation attribute at the root element. Here is an example of how this works on the SXP Contract Schema:

<?xml version="1.0"?>
<contract xmlns="[http://www.w3schools.com](http://www.w3schools.com)"  
xmlns:xsi="[http://www.w3.org/2001/XMLSchema-instance](http://www.w3.org/2001/XMLSchema-instance)"  
**xsi:schemaLocation**="[urn:oasis:names:tc:eContracts:1:0](urn:oasis:names:tc:eContracts:1:0) SXPContract.xsd">

This attribute has two values, separated by a space. The first value is the namespace to use. The second value is the location of the XML schema to use for that namespace.

The namespace from schemaLocation has to be the same as the one on the XSD document under the attribute targetNamespace. Certainly, on SXPContract.xsd we have:

<?xml version="1.0" encoding="UTF-8"?>
<xs:schema
...
targetNamespace="urn:oasis:names:tc:eContracts:1:0">

More information on this: W3Schools: the schema element