MSXML6 SDK documentation online

MSXML6 SDK documentation is online now. In fact it's "multi-version" documentation, which covers MSXML3 through MSXML6.

So, what's new in MSXML6? Looks like it's security tightening, XML Schema support improvements and removals:

What's New in MSXML 6.0
MSXML 6.0 shipped with SQL Server 2005. It also shipped as a Web release. The following is a high-level summary of features that were introduced with MSXML 6.0.

• Security
  
  A number of enhancements have been made to MSXML 6.0 to eliminate security threats. Additionally, some features that are insecure, such as DTDs and inline schemas, have been turned off by default. For more information, see MSXML Security Overview.
  
• XDR Schema Support Removed
  
  XML Data Reduced (XDR) schema support has been removed. For more information, see Removal of XDR Schema Support.
  
• Improvements in XSD Standards Compliance
  
  MSXML 6.0 has improved XSD schema standards compliance. For more information, see Improvements in XSD Standards Compliance.
  
• Improvements in Schema Cache Behavior
  
  MSXML 6.0 has changed the behavior of the XSD schema cache. The new version is less ambiguous when there are name collisions. For more information, see Improvements in Schema Cache Behavior.
  
• XML Digital Signature Removed
  
  MSXML 6.0 removed support for XML digital signatures. For more information, see XML Digital Signatures.
  
• Other Changes in MSXML 6.0
  
  There are a number of other changes in MSXML 6.0. A few of the changes may require modifications to applications. For more information, see Changes in MSXML 6.0.

It's a pity support for the XML Digital Signature was removed. It was implemented for Office and most likely Microsoft doesn't want a burden of supporting it for all MSXML users. Another sad fact is an obvious fork of MSXML - MSXML5 is actually "MSXML 5.0 for Microsoft Office Applications", not available as a separate download. That was probably not a good idea.