CHAPTER 8
596
Interactive Features
KEY
TYPE
VALUE
P
St
text string
integer
(Optional)
The label prefix for page labels in this range.
(Optional)
The value of the numeric portion for the first page label in the range. Sub-
sequent pages are numbered sequentially from this value, which must be greater than or
equal to 1. Default value: 1.
8.3.2 Articles
Some types of documents may contain sequences of content items that are logi-
cally connected but not physically sequential. For example, a news story may be-
gin on the first page of a newsletter and run over onto one or more
nonconsecutive interior pages. To represent such sequences of physically discon-
tiguous but logically related items, a PDF document may define one or more
arti-
cles (PDF 1.1).
The sequential flow of an article is defined by an
article thread;
the
individual content items that make up the article are called
beads
on the thread.
PDF viewer applications can provide navigation facilities to allow the user to fol-
low a thread from one bead to the next.
The optional
Threads
entry in the document catalog (see Section 3.6.1, “Docu-
thread dictionaries
document’s articles. Each individual bead within a thread is represented by a
bead
dictionary
F
entry points to the first bead in
the thread; the beads are chained together sequentially in a doubly linked list
through their
N
(next) and
V
(previous) entries. In addition, for each page on
which article beads appear, the page object (see “Page Objects” on page 144)
should contain a
B
entry whose value is an array of indirect references to the
beads on the page, in drawing order.
TABLE 8.11 Entries in a thread dictionary
KEY
TYPE
VALUE
Type
name
dictionary
dictionary
(Optional)
The type of PDF object that this dictionary describes; if present, must be
Thread
for a thread dictionary.
(Required; must be an indirect reference)
The first bead in the thread.
(Optional)
A thread information dictionary containing information about the thread,
such as its title, author, and creation date. The contents of this dictionary are similar
to those of the document information dictionary (see Section 10.2.1, “Document In-
F
I