When validating a map using the BizTalk Mapper the only output is an Xsl file (the compiled map) and an extensionobjects xml file.
The extensionobjects xml file contains references to external .Net assemblies that are called from within the map. If you’re are not using any scripting functoids that reference external assemblies this file is empty.
In the output window of Visual Studio there should be 2 hyperlinks – the first for the Xsl file and second for the extnsionobjects file.