SECTION 4.10
365
Optional Content
KEY
TYPE
VALUE
Intent
name or array
(Optional)
A single intent name or an array containing any combination of
names. PDF 1.5 defines two names,
View
and
Design
, that indicate the intended
use of the graphics in the group. Future versions may define others. A process-
ing application can choose to use only groups that have a specific intent and ig-
nore others.
Default value:
View
. See “Intent” on page 368 for more information.
Usage
dictionary
(Optional)
A
usage dictionary
describing the nature of the content controlled by
the group. It may be used by features that automatically control the state of the
group based on outside factors. See “Usage and Usage Application Dictionaries”
In its simplest form, each dictionary contains a
Type
entry and a
Name
for pre-
sentation in a user interface. It may also have an
Intent
entry that describes its in-
tended use (see “Intent” on page 368) and a
Usage
entry that describes the nature
of its content (see “Usage and Usage Application Dictionaries” on page 380).
Individual content elements in a document specify the optional content group or
groups that affect their visibility (see Section 4.10.2, “Making Graphical Content
tent group is said to belong to that group.
A group is assigned a state, which is either
ON
or
OFF
. States are not themselves
part of the PDF document but can be set programmatically or through the viewer
user interface to change the visibility of content. When a document is first
opened, the groups’ states are initialized based on the document’s default config-
uration dictionary (see “Optional Content Configuration Dictionaries” on page
In the typical case, content belonging to a group is visible when the group is
ON
and invisible when it is
OFF
. In more complex cases, content can belong to multi-
ple groups, which may have conflicting states. These cases are described by the
use of optional content membership dictionaries, described in the next section.
Optional Content Membership Dictionaries
As mentioned above, content typically belongs to a single optional content group
and is visible when the group is
ON
and invisible when it is
OFF
. To express more
complex visibility policies, content should declare itself not to belong directly to