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       SECTION 10.6                                                             Logical Structure



       A structure element dictionary can include one or more marked-content se-
       quences as content items by referring to them in its K entry (see Table 10.10). This
       reference can have two forms:

       • A dictionary object called a marked-content reference. Table 10.11 shows the
         contents of this type of dictionary, which specifies the marked-content identifi-
         er, as well other information identifying the stream in which the sequence is
         contained. Example 10.8 illustrates the use of a marked-content reference to the
         marked-content sequence shown in Example 10.7.
       • An integer that specifies the marked-content identifier. This can be done in the
         common case where the marked-content sequence is contained in the content
         stream of the page that is specified in the Pg entry of the structure element dic-
         tionary. Example 10.9 shows a structure element that has three children: a
         marked-content sequence specified by a marked-content identifier, as well as
         two other structure elements.

       Example 10.8

         1 0 obj                              % Structure element
            << /Type /StructElem
                /S /P                         % Structure type
                /P …                          % Parent in structure hierarchy
                /K << /Type /MCR
                      /Pg 2 0 R               % Page containing marked-content sequence
                      /MCID 0                 % Marked-content identifier
                   >>
            >>
         endobj


                   TABLE 10.11 Entries in a marked-content reference dictionary
KEY        TYPE           VALUE

Type       name           (Required) The type of PDF object that this dictionary describes; must be MCR
                          for a marked-content reference.

Pg         dictionary     (Optional; must be an indirect reference) The page object representing the page
                          on which the graphics objects in the marked-content sequence are rendered.
                          This entry overrides any Pg entry in the structure element containing the
                          marked-content reference; it is required if the structure element has no such en-
                          try.

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