Categories should be added to http://pkgs.alpinelinux.org/packages for better filters like "terminal" or "desktop", "webserver", ...
If Alpine is ever going to have a useful graphical package manager, this is necessary. I would suggest using the same format that is in *.desktop files and if no desktop file is provided in the package, parse the file list for specific files or directories such as:
To further improve the situation, I would also add a field corresponding to the MimeType entry in the *.desktop file so that the package manager could automatically provide a list of usable applications to install (via wrapper around xdg-open??)
... and the final bonus, the Icon entry ...for obvious reasons in a graphical package manager, but it could also be used for an online distro iso/img builder
For a web-based example that would work over ssh (links), in the console (netsurf-framebuffer) or in X or Wayland (via browser) see: http://hg.slitaz.org/tazpkg/file/