Metadata
Amiga could save metadata into hunks, as the hunk structure could be easily adapted to support this feature, but the hunk format of executables was abandoned in favour of ELF and there is no central authority (as the dismissed Commodore) which could implement this feature as one of the Amiga standards.
Amiga saves some metadata into sidecar files known as ".info" (so called from the name of their extension suffix).
".info" files are created any time a project (datafile) is saved on disk. Example: When user saves a file called "MyProject" there will be created two files on disk called "MyProject" and MyProject.info".
Into the "MyProject" file are saved real data of the project file, while in "MyProject.info" file there will be stored the icon, and the information regarding the software which originated the file, so any time the project icon is invoked by clicking on it with mouse, there will be opened the parent software (users can change any time this information, allowing other programs to believe they created the project file rather than the original software which physically created it).
Into AmigaOS does not exist Application Binding as in other systems like MacOS.
Into the ".info" file are stored also some particular characteristics of the project file and the user comments.
".info" files do not appear on the Workbench Screen (Workbench is the default Amiga Desktop GUI). On the desktop screen it appears only the icon of the project file taken out of the "info file". In fact the icon is the virtual medium that connects the project itself and the metadata stored into ".info".
When the user clicks on the icon with left button of the mouse, the project ".info" calls the program which originated it. When the user clicks on the icon with the right button, then a dialog box will appear, allowing the user to interact with metadata contained into ".info file".
The ".info" files are copied or moved together with their associated project file, by moving the icon with the mouse, and can be viewed as standalone file through command line interfaces of Amiga such as AmigaShell, or using third party filemanagers or directory listers like Directory Opus or DiskMaster.
If the ".info" file represents an executable program, then into the ".info" are stored information about the stack of RAM buffers that could be reserved to the executable file (exp: 4096 or 8192 or 16384 or more bytes of RAM) and even the arguments that could be invoked by using a command line interface. For example into Amiga it is usual that a program could open its own graphic user interface screen independent from the desktop screen. By invoking arguments such as "Screen=800x600" and "Depth=8" into the info file dialog box, the user can save these informations into the associated ".info file" and then AmigaOS will open any time the productivity software into its own screen sized 800×600 with 8 bits of colour depth (equal to 256 colors).
The same behaviour is obtained by invoking the productivity software into a command line interface by typing "nameofproductivitysoftware /screen800x600 /depth8".
This method of storing arguments associated with software into preference informations contained in ".info" files allows the Amiga users to use either command line interfaces or GUI graphical interfaces at the same time obtaining same results.
The user has also the choice of deleting ".info" files, but then he will renounce the benefits of having an icon representing the project file on the desktop, and will renounce to all the metadata contained into it.
Read more about this topic: Amiga Hunk