http://citeseer.ist.psu.edu/gifford91semantic.html

@Thrax: The subdirectories contain links to the files that match both the tag of the current directory and the tag of each subdirectory. That is, they contain the two-tag matches. The subdirectories of those subdirectories are the three-tag matches, and so forth. tag(1) makes the subdirectories based on the set of tags on each file; adding a tag can create additional directories, while deleting a tag may cause the removal of directories (if that was the last use of the tag). Don’t rename the tag directories! This operation needs to be added to tag(1) to be safe: the tag sets of each file with the given tag (to be renamed) need to be updated as well.

— Stephen

I can see it would be handy with pipes, like %tag print_me|lpr And I guess renaming a tag would be easy when browsing the tag directory. I hear Flickr has introduced ‘for:person’ tags. Seems like a slippery slope to complexity.

@Marty: you’re right that a filesystem implementation, where the directories can be synthesized as needed, can avoid some of the combinatorial problems, but it opens the system to a different type of resource exhaustion, as an antagonist can open deep paths and exhaust kernel memory. This moves the denial of service from per-filesystem to system wide. Ultimately, I think a cap on the depth of the link set is needed by any implementation.

@Travis and Alex: I’m a bit ignorant about WinFS’s capabilities, but standardized user and application metadata conventions sound like the right direction for making categorization a meaningful addition to an operating system’s programming model. The XTend demos show that there’s a benefit to representing such attributes in file browsers, and not just via a command line interface.

— Stephen

That page links to 2 flash demos. http://www.base4.net/xtend/interface.htm http://www.base4.net/xtend/search.htm

The second demo is especially relevant. XTend allowed you to filter a file system by relationship. One type of relationship I supported was from File to Tag (or what I called Concepts, note: this was before ‘Tagging’ became so hot). So this allowed you to filter the filesystem by tag or tags.

I would love to hear your thoughts on XTend, even though I am no longer working on it.

It’s a shame it won’t be ready for Longhorn and will instead be an add-on.

Hopefully WinFS will finally allow Windows NTFS to have unix style soft/hard links as “shortcuts” are a half arsed at best (even tried to open a shortcut in your text editor or mp3 player?).

You might be able to eliminate your combinatorial explosion of tag subdirectories by using a virtual filesystem (http://lwn.net/Articles/13325/). Such an approach would come at the cost of platform-specificity, but since you’re using symlinks already, I suspect that’s acceptable.

Nice work!

• Marty