What is an XML schema?
An XML schema is a file in which the definition of an XML dataset is recorded. The most commonly used method of defining an XML schema is in an XSD file, short for XML Schema Definition. The XSD file expresses which variables and data types are allowed to be used in the corresponding XML file.
When creating an XML file, the data in the XML file can be forced to be validated according to the definitions of the corresponding XSD file. After this, when the original XML file is being processed, the XML parser first validates whether the data complies with the checks specified in the XSD file. Only once the checks have been approved will the data in the XML source file be processed by the XML parser.