Servlet spec, the spec which defines the term Web Application, defines the overall structure of a
Web Application as a hierrachical arrangement of files (and directories), but does not mandate them to be
available in a hierarchical file system per se. See section #10.4 of Servlet 3.0 spec, which mentions
the following:
This specification defines a hierarchical structure used for deployment and
packaging purposes that can exist in an open file system, in an archive file, or in
some other form. It is recommended, but not required, that servlet containers
support this structure as a runtime representation.
A WAB provides such a view of web application which is actually composed of a host OSGi bundle and zero or
more attached fragment bundles.