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          SECTION 4.10                                                            Optional Content



          Optional Content Properties Dictionary

          The optional OCProperties entry in the document catalog (see Section 3.6.1,
          “Document Catalog”) holds the optional content properties dictionary, which con-
          tains a list of all the optional content groups in the document, as well as informa-
          tion about the default and alternate configurations for optional content. This
          dictionary is required if the file contains any optional content; if it is missing, a
          PDF consumer should ignore any optional content structures in the document.

          This dictionary contains the following entries:

                      TABLE 4.50 Entries in the optional content properties dictionary
KEY           TYPE             VALUE

OCGs          array            (Required) An array of indirect references to all the optional content groups in
                               the document (see Section 4.10.1, “Optional Content Groups”), in any order.
                               Every optional content group must be included in this array.

D             dictionary       (Required) The default viewing optional content configuration dictionary (see
                               “Optional Content Configuration Dictionaries,” below).

Configs       array            (Optional) An array of alternate optional content configuration dictionaries (see
                               “Optional Content Configuration Dictionaries,” below) for PDF processing ap-
                               plications or features.


          Optional Content Configuration Dictionaries

          The D and Configs entries in Table 4.50 are configuration dictionaries, which rep-
          resent different presentations of a document’s optional content groups for use by
          PDF processing applications or features. The D configuration dictionary specifies
          the initial state of the optional content groups when a document is first opened.
          Configs lists other configurations that may be used under particular circumstanc-
          es. The entries in a configuration dictionary are shown in Table 4.51.

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