Uniform Type Identifier
From Wikipedia, the free encyclopedia
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.[1] 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 time, filename extension, or type or creator code.[1][2]
UTIs use a reverse-DNS structure. UTIs support multiple inheritance, allowing multimedia files to be identified as not as single type (as in MIME), but as all the types it is; an identifier can inherit from public.audio, public.video, public.text, public.image, etc.[1] UTIs are stored as Core Foundation strings; allowable characters are A–Z, a–z, 0–9, "-", ".", and all Unicode characters above U+007F.[2]
The public.* domain is only editable by Apple and contains the base data types used by all UTIs.[1]
| 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:[1]
| 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."[2]
[edit] References
- ^ a b c d e Siracusa, John (2005-04-28). File types revisited. Operating System Reviews: Mac OS X 10.4 Tiger. Ars Technica. Retrieved on 2007-12-08.
- ^ a b c Uniform Type Identifiers Overview. Apple Developer Connection Reference Library. Apple (2007-10-29). Retrieved on 2007-12-08.
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