Uniform Type Identifier Information & Uniform Type Identifier Links at HealthHaven.com

A Uniform Type Identifier (UTI) is a string defined by Apple Inc. that uniquely identifies the type of a class of items. Added in Apple's Mac OS X 10.4 operating system, UTIs are used to identify the type of files and folders, clipboard data, bundles, aliases and symlinks, and streaming data. Mac OS X's desktop search technology, Spotlight, uses UTIs to categorize documents. One of the primary design goals of UTIs was to eliminate the ambiguities and problems associated with inferring a file's content from its MIME type, filename extension, or type or creator code.^[1]

UTIs use a reverse-DNS structure. UTIs support multiple inheritance, allowing multimedia files to be identified as more than just a single type (as in MIME), but as all the types the files are. An identifier can inherit from public.audio, public.video, public.text, public.image, etc. UTIs are stored as Core Foundation strings. Allowable characters are A-Z, a-z, 0-9, "-", ".", and all Unicode characters above U+007F.^[1]

The public.* domain is only editable by Apple and contains the base data types used by all UTIs.

Identifier	Conforms to	Comment
public.item		base class in the physical hierarchy
public.content		base class for all document content
public.data	public.item	base class for all files, byte streams, pasteboard, etc.
public.image	public.data, public.content	base class for all images

UTIs are even used to identify other file type identifiers:

Identifier	Conforms to	Comment
public.filename-extension	public.case-insensitive-text	Filename extension.
public.mime-type	public.case-insensitive-text	MIME type.
com.apple.ostype	public.text	Four-character code (type OSType).
com.apple.nspboard-type	public.text	NSPasteboard type.

Dynamic UTIs can be created as needed by applications; these have the prefix dyn. and take the form of "a UTI-compatible wrapper around an otherwise unknown filename extension, MIME type, OSType, and so on."^[1]

[edit] Third party UTIs

Apple provides a large collection of system-declared Uniform Type Identifiers. Third-party applications can add UTIs to the database maintained by Mac OS X by "exporting" UTIs declared within the application package. Because new UTIs can be declared to "conform to" existing system UTIs, and declarations can associate the new UTIs with file extensions, an exported declaration alone can provide the operating system with enough information to enable new functionality, such as enabling Quick Look for new file types.

[edit] Looking up a UTI

To get the UTI of a given file, use the mdls (meta data list, part of Spotlight) command in the Terminal.

[edit] References

^ ^a ^b ^c "Uniform Type Identifiers Overview". Apple Developer Connection Reference Library. Apple. 2007-10-29. http://developer.apple.com/documentation/Carbon/Conceptual/understanding_utis. Retrieved 2007-12-08.

"Introduction to Uniform Type Identifiers", Apple Developer Documentation

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[adc-0] "Uniform Type Identifiers Overview". Apple Developer Connection Reference Library. Apple. 2007-10-29. http://developer.apple.com/documentation/Carbon/Conceptual/understanding_utis. Retrieved 2007-12-08.

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