SECTION F.4
1055
Access Strategies
F.4.5 Following an Article Thread
As indicated earlier, the bead dictionaries for any article thread that visits a given
page are located with that page. This enables the bead rectangles to be activated
and proper cursor feedback to be shown.
If the user follows a thread, the viewer application can obtain the object number
from the
N
or
P
entry of the bead dictionary. This identifies a target bead, which
is located with the page to which it belongs. Given this object number, the viewer
application can go to that page, as discussed in Section F.4.3, “Going to Another
F.4.6 Accessing an Updated File
As stated earlier, if a Linearized PDF file subsequently has an incremental update
appended to it, the linearization and hints are no longer valid. Actually, this is not
necessarily true, but the viewer application must do some additional work to val-
idate the information.
When the viewer application sees that the file is longer than the length given in
the linearization parameter dictionary, it must issue an additional transaction to
read everything that was appended. It must then analyze the objects in that up-
date to see whether any of them modify objects that are in the first page or that
are the targets of hints. If so, it must augment its internal data structures as neces-
sary to take the updates into account.
For a PDF file that has received only a small update, this approach may be worth-
while. Accessing the file this way is quicker than accessing it without hints or re-
trieving the entire file before displaying any of it.