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         SECTION 8.2                                                 Document-Level Navigation



         A collection dictionary specifies the viewing and organizational characteristics of
         portable collections. If this dictionary is present in a PDF document, the user in-
         terface presents the document as a portable collection. The EmbeddedFiles name
         tree specifies file attachments (see Section 3.10.3, “Embedded File Streams).

         When a PDF 1.7-compliant viewer application first opens a PDF document con-
         taining a collection, it must display the contents of the initial document, along
         with a list of the documents present in the EmbeddedFiles name tree. The docu-
         ment list must include the additional document information specified by the col-
         lection schema. The initial document can be the container PDF or one of the
         embedded documents.

         The page content in the initial document typically contains information that
         helps the viewer understand what is contained in the collection, such as a title
         and an introductory paragraph.

         The file attachments comprising a collection are located in the EmbeddedFiles
         name tree. All attachments in that tree are in the collection; any attachments not
         in that tree are not.

         Table 8.6 describes the entries in a collection dictionary.

                              TABLE 8.6 Entries in a collection dictionary
KEY                        TYPE          VALUE

Type                       name          (Optional) The type of PDF object that this dictionary describes; if
                                         present, must be Collection for a collection dictionary.

Schema                     dictionary    (Optional) A collection schema dictionary (see Table 8.7). If absent,
                                         the PDF viewer application may choose useful defaults that are
                                         known to exist in a file specification dictionary, such as the file
                                         name, file size, and modified date.

D                          byte string   (Optional) A string that identifies an entry in the EmbeddedFiles
                                         name tree, controlling the document that is initially presented in
                                         the user interface. If the D entry is missing or in error, the initial
                                         document is the one that contains the collection dictionary.

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