A posting from Dare Obasanjo (Microsoft) announces the release of MSXML 4 SP 1 (Microsoft XML Core Services). This version 40SP1 (14-March-2002) release "offers a number of new features and improvements over the MSXML 3.0, including support for the XML Schema language and substantially faster parser and XSLT engine. MSXML 4.0 SP1 is a complete replacement for MSXML 4.0 RTM and provides a number of bug fixes. It cannot replace MSXML 3.0, because some obsolete and non-conformant features are no longer supported. MSXML 4.0 installs side by side with MSXML 3.0 and earlier, without any interference." MSXML 4 SP 1 is available for Windows 95 & 98, NT 4.0 & 2000, Windows Me, and Win XP.

Comment from Rick Jelliffe on XML-DEV: "We use MSXML 4 in our free Schematron Validator utility. We have had thousands of downloads and only a handful of comments about suspected validation problems with XML Schemas. As negative as I am about [...], I cannot be positive enough about MSXML 4: the XSLT is great, the transcoding works nice and strictly, and the Schema implementation seems good, at least for conservatively written schemas. Last year, it seemed that when there was a difference between what Spy allowed and what MSXML 4 allowed, MSXML usually seemed to be correct. But Spy has been improving, and the most recent comments we had from a user concerning a difference was pretty tricky... I second the call for MS to release a list of what bugs have been fixed, and indeed a list of known bugs. HP was famous for making its bug lists public, and since validation is used for contracts and for systems acceptence, it is very important for people to know the particular limitations of their tools. In the particular case of schema tools, a bug does not become critical to fix when a large-enough number of people complain about it, it is critical fix all bugs."

System/Installation: available for Windows 95 & 98, NT 4.0 & 2000, Windows Me, Win XP. Requires Windows Installer 2.0. "MSXML 4.0 install over MSXML 4.0 Beta 1 (April 2001 release) is not supported. If you do that directly it will affect a number of applications, including Visual Studio.Net. That means that if you had the April technology preview of MSXML 4.0 (Beta 1), you will also have to unregister existing msxml4.dll, uninstall/remove it, and reregister MSXML 3.0 (xmlinst.exe is very useful in this case). When you have completed these steps, you can proceed with the installation of MSXML 4.0 RTM. Upgrade from beta 4.0 releases to RTM and later is not supported. You have to uninstall all technology preview releases from your computer prior to installing the MSXML 4.0 RTM version. You might have to delete msxml4*.dll files in your system (system32) directory manually."