Whether or not you completely understand the XTAB language ...
You have looked over the XTAB documentation and realize that XTAB is essentially an ad hoc query/cross-tabulation report tool for flat files.
You realize that XTAB, being based on Perl, is essentially free.
You have looked at the "TRY IT" page and realize the XTAB program is running on a web server against a flat file on that server.
Any organization with access to a web server
... that supports Perl
... ... and has the ability to place flat files on that server
... ... ... may open those files to query processing by field (the public and/or selected) users
... ... ... ... via a web browser.
Query users could be required to sign-on, monitored, charged, etc ...
No 5 million dollar Oracle database, with sophisticated 3rd party query tools, and the associated technical and maintenance support is required.
While not perfect for ALL applications, it could be beneficial for MANY applications.
An economical and seamless solution to a wide range of todays information distribution challenges.