A file with .adb extension is a database file created with Alpha Five (now known as Alpha Anywhere). It contains the filenames of all tables and sets that are members of the project workspace. In addition, it contains the names of all the libraries that are incorporated in the workspace. Alpha Anywhere is an IDE used to develop web applications. In addition to ADB files, an Alpha Anywhere’s workspace may contain many files that starts table’s or set’s name, but have different file extensions.
ADB File Format - More Information
The internal file format information of .adb files is not available for developer’s reference.