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                                                  183
       SECTION 3.10                                                             File Specifications



KEY    TYPE          VALUE

F      string        (Required if the DOS, Mac, and Unix entries are all absent; amended with the UF entry
                     for PDF 1.7) A file specification string of the form described in Section 3.10.1, “File
                     Specification Strings,” or (if the file system is URL) a uniform resource locator, as de-
                     scribed in Section 3.10.4, “URL Specifications.”
                     Note: It is recommended that the UF entry be used in addition to the F entry. The UF en-
                     try provides cross-platform and cross-language compatibility and the F entry provides
                     backwards compatibility.

UF     text string   (Optional, but recommended if the F entry exists in the dictionary; PDF 1.7) A Unicode
                     text string that provides file specification of the form described in Section 3.10.1, “File
                     Specification Strings.” Note that this is a Unicode text string encoded using PDFDocEn-
                     coding or UTF-16BE with a leading byte-order marker (as defined in Section , “Text
                     String Type”). The F entry should always be included along with this entry for back-
                     wards compatibility reasons.

DOS    byte string   (Optional) A file specification string (see Section 3.10.1, “File Specification Strings”)
                     representing a DOS file name.
                     Note: Beginning with PDF 1.7, use of the F entry and optionally the UF entry is recom-
                     mended in place of the DOS, Mac or Unix entries.

Mac    byte string   (Optional) A file specification string (see Section 3.10.1, “File Specification Strings”)
                     representing a Mac OS file name.
                     Note: Beginning with PDF 1.7, use of the F entry and optionally the UF entry is recom-
                     mended in place of the DOS, Mac or Unix entries.

Unix   byte string   (Optional) A file specification string (see Section 3.10.1, “File Specification Strings”)
                     representing a UNIX file name.
                     Note: Beginning with PDF 1.7, use of the F entry and optionally the UF entry is recom-
                     mended in place of the DOS, Mac or Unix entries.

ID     array         (Optional) An array of two byte strings constituting a file identifier (see Section 10.3,
                     “File Identifiers”) that is also included in the referenced file. The use of this entry im-
                     proves an application’s chances of finding the intended file and allows it to warn the
                     user if the file has changed since the link was made.

V      boolean       (Optional; PDF 1.2) A flag indicating whether the file referenced by the file specifica-
                     tion is volatile (changes frequently with time). If the value is true, applications should
                     never cache a copy of the file. For example, a movie annotation referencing a URL to
                     a live video camera could set this flag to true to notify the application that it should
                     reacquire the movie each time it is played. Default value: false.

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