OPML File Type on Macs
I was fixing a bug in OmniOutliner where it wouldn’t open a file with an uppercase .OPML suffix. I did some digging, and the fix was to register the app as handling the com.apple.news.opml file type.
[…]
OPML — Outline Processor Markup Language — was invented in 2000 by Dave Winer at UserLand Software. It’s not Apple’s format, and the correct file type is org.opml.opml.
I seem to recall a similar issue with a non-standard UTI for Markdown.
Non-standard UTIs are a real pain in the (La)TeX world, since there are multiple definitions out there, and Launch Services doesn't resolve conflicts in a way that users can understand or debug. The fact that Apple is a chokepoint for public.* UTIs and others just makes it worse; Apple has made it pretty clear that they don't care. Want to work with a .img remote sensing file? Too bad: Apple says that's com.apple.disk-image-ndif. I wrote a whitepaper for the MacTeX working group a few years ago with a proposal for unified UTIs, but it never went anywhere. https://github.com/amaxwell/mactex_uti/blob/master/mactex_uti.pdf