Bigtop is a language for describing the data of a web application.
Usually this data will be stored in a relational database. Once you
have a description of your data, you can generate a web application
from it. This includes all the pieces you need like: the sql
statements ready for feeding to your database command line tool, the
httpd.conf you need to Include in the httpd.conf on your system, the
modules that will handle the web requests, the models that make the
database tables look like classes, etc.

If you need to alter the data model in the future, you can change your
original description to match the new reality, then regenerate the
application without fear of losing hand written code (though you may
have to modify some of it to reflect the new reality).