The XML support in Internet Explorer is built into the Microsoft XML (MSXML package). This package was called the Microsoft XML Parser until version 4.0, when it was named the Microsoft XML Core Services. Version 4.0 is the version that supports full schemas, also called XML Schema Definition Language (XSD) schemas. Before version 4.0, the MSXML package supported a smaller and different version of XML schemas, which Microsoft calls XML-Data Reduced (XDR) schemas. You can see the support for XML schemas by MSXML version in Table 5-1.
|MSXML||No support for schemas|
|MSXML 2.0||Support for XDR schemas|
|MSXML 2.6||Support for XDR schemas|
|MSXML 3.0||Support ...|