On the other hand, AppleScript provides a way to set “default application” in the “System Events” dictionary, so there’s no missing programmatic capability. Content developers can just use an AppleScript system service that saves the file with the current application as default.

While this generally makes sense, it is not without its drawbacks. For example, I have an application called LaTeX-iT. I do not know the reverse DNS name for this application. Instead, I have to go to my Preferences directory and obtain a listing for files matching *[Ll]a[Tt]e[Xx]* just to find the preference file. If the application name were first, I could just scroll down the total list to the “L” section and would have a pretty easy time finding things.

For the record: the name is fr.club.ktd.LaTeXiT.

“UTIs provide a standardized way for defining data anywhere in the system, one that transcends the Type/Creator Code’s limited concept of a single app that creates given file types.”

Which clarifies the subject of distinguishing between file formats / types.

I thought (this part of) walter’s nutshell explained it well enough …

“All the application has to do is declare a new type to be an extension of the common format, and register itself as the handler for that custom type. Any files it creates can list themselves as the specialized type. If the document is an HTML document, any program can declare a type like com.company.program.html to extend public.html, and then handle that specialized type.”

But then walter later clarifies:

“However, there should be a way to declare a file as a special instance of a more generic type that does not depend on extensions.”

Is this not what happens in a UTI, as per the flow chart?

http://images.appleinsider.com/uti092209.3.png

Better explained than I, going off half cocked (feature, not bug :-)

http://www.roughlydrafted.com/2009/09/07/inside-mac-os-x-snow-leopard-malware-protection/#comment-20674

It seems to me the best way to do this is what Siracusa mentions: define an extended attribute to store the UTI.

Extensions are useful, which is something old-time Mac OS guys don’t always understand: when you aren’t using a graphical interface to present a pretty icon describing the file type, the extension is a quick indicator. However, there should be a way to declare a file as a special instance of a more generic type that does not depend on extensions.

Most old time Mac OS users who use and like the file creator feature of the previous versions of Mac OS/OS X aren’t going to be happy with needing a new file name extension for existing file types in order to do what they used to do with creator codes.

While there is a solution, in order to make it work in the current version of Snow Leopard, the developer has to define a new file extension. That means that file.html is now file.bbedit-html. Read the article from Ars Technica. It explains this in detail.

From http://arstechnica.com/staff/fatbits/2009/09/metadata-madness.ars:
“Given a file on disk, Mac OS X provides a way to get a UTI representation of that file’s type. This may lead you to believe that, like the classic Mac OS type codes, there is a storage location somewhere in the file system for the UTI of each file. This is not the case. Instead, Mac OS X derives the UTI from other information, primarily—and tragically—from the file name extension.”

The article implies that you can use a standard extension like .jpg and have an application override the default application for .jpg when a file is saved. This simply isn’t true in Snow Leopard. Dan acknowledges that in his follow up.

“So no, UTI isn’t a drop in replacement for Creators that does exactly the same thing, because doing exactly the same thing is not the desired behavior (from Apple’s perspective).”

I agree. The old behavior is confusing and inconsistent to most users. Some few old-time Mac OS users are going to have to find a simple change to their work flow such as drag and drop of files on an open application or using a control-click Open With to open files in a different application from the default. This is better than the existing system where you never really know which application is going to open for a particular file without using Open With.

Any application that wants to retain the old behavior is going to have to define its own extension. Instead of file.html it will be file.bbedit-html. When done editing/authoring, export the file to use the standard extension.

It seems like apple is the only *company* that puts in the effort to rethink things like this. Some companies have *people* or *departments* that work on these things, but in the end, the companies tend to worship the status quo and are typically afraid to break any eggs, even as they claim to want to make omelets. Apple is unique in that they consistently quest for innovative approaches to genuinely enhance usability or make something better. Gotta love it (even if it seems temporarily annoying.)

To summarize: “I didn’t read the article carefully.”