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PDF20 Spec 14 Page Piece
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14.5 Page-piece dictionaries A page-piece dictionary (PDF 1.3) may be used to hold private PDF processor data. The data may be associated with a page or form XObject by means of the optional PieceInfo entry in the page object (see "Table 31 — Entries in a page object") or form dictionary (see "Table 93 — Additional entries specific to a Type 1 form dictionary"). Beginning with PDF 1.4, private data may also be associated with the PDF document by means of the PieceInfo entry in the document catalog dictionary (see "Table 29 — Entries in the catalog dictionary"). NOTE
PDF writers can use this dictionary as a place to store private data in connection with that document, page, or form. Such private data can convey information meaningful to the PDF processor that produces it (such as information on object grouping for a graphics editor or the layer information used by Adobe Photoshop®) but can be ignored by general-purpose PDF processors.
As "Table 350 — Entries in a page-piece dictionary" shows, a page-piece dictionary may contain any number of entries, each keyed by the name of a distinct PDF processor or of a well-known data type recognised by a family of PDF processors. The value associated with each key shall be a data dictionary containing the private data that shall be used by the PDF processor. The Private entry may have a value of any data type, but typically it is a dictionary containing all of the private data needed by the PDF processor other than the actual content of the document, page, or form. Table 350 — Entries in a page-piece dictionary Key
Type
any valid second-class name dictionary
© ISO 2020 – All rights reserved
Value A data dictionary (see "Table 351 — Entries in a data dictionary").
719
ISO 32000-2:2020(E)
Table 351 — Entries in a data dictionary Key
Type
Value
LastModified
date
(Required) The date and time when the contents of the document, page, or form were most recently modified by this PDF processor.
Private
(any)
(Optional) Any private data appropriate to the PDF processor, typically in the form of a dictionary.
The LastModified entry indicates when a PDF processor last altered the content of the document, page or form. If the page-piece dictionary contains several data dictionaries, their modification dates can be compared with those in the corresponding entry of the page object or form dictionary (see "Table 31 — Entries in a page object" and "Table 93 — Additional entries specific to a Type 1 form dictionary"), or the ModDate entry of the document information dictionary (see "Table 349 — Entries in the document information dictionary"), to ascertain whether the data dictionary corresponds to the current content of the document, page or form. Because some platforms may use only an approximate value for the date and time or may not deal correctly with differing time zones, modification dates shall be compared only for equality and not for sequential ordering.
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