I'm not sure that I understand.
When I add an XML file to a database, IMatch indexes the file, and even displays the contents of the XML file in the Quick Preview panel, with proper indentation and highlighting.
Neither IMatch nor ExifTool will do any further analysis of the contents of arbitrary text files or anything, if this is what you expect. Every XML file is different and an application has to understand the XML and the data it contains to process it in any further way. Just that a file is in XML format does not mean a thing. It just tells you that the data in the file is in XML format, but not what the data actually means.
I think what you mean is that ExifTool extracts some of the XML data and displays it when used from the command line? This is not how it works when IMatch uses ExifTool and IMatch does not receive any data for XML files. In command line, ExifTool just dumps the individual nodes in the XML file. This data is of no use for IMatch and cannot be mapped into the metadata tag schema IMatch uses to corporate with ExifTool.
And, please, read the board info before you post. This board is for posting tutorials and for giving other users tips. Not for asking questions. I have moved your post to the General Discussions board.