Today, most developers prefer to store information in databases. But plain filesystems were used for years, and are still used, to store information, commonly in files of heterogeneous formats that are organized in directory trees.
This approach is a very flexible and natural way to create hierarchical organized structures of documents.
We can devise a formal notation to describe a filesystem tree structure, similar to a grammar, assuming that filenames can be considered terminal symbols, and directory names non-terminal symbols. This specification would allow to derive correct language sentences (combination of terminal symbols) and to associate semantic actions, that can produce arbitrary side effects, to each valid sentence, just as we do in common parser generation tools. These specifications can be used to systematically process files in directory trees, and the final result depends on the semantic actions associated with each production rule.
In this paper we revamped an old idea of using a domain specific language to implement these specifications similar to context free grammars. And introduce some examples of applications that can be built using this approach
