XFA Specification
Chapter 15, Template Specification
Guide to the Template Specification
420
Regular Properties
Regular properties can be added to the element without regard to other properties in the element. The
element descriptions in this specification use the term
Property
to identify such regular properties.
In the case of elements, occurrence constraints must be honored.
One-of Properties
There are occasions where an element supports mutually-exclusive properties. For unstructured
properties, an attribute enumeration represents the mutually-exclusive values, and these are not
distinguished from regular properties. However, for structured properties, the entire structures are likely
mutually-exclusive.
The element descriptions in this specification use the term
One-of property
to identify mutually-exclusive,
structured properties. The element must hold at most one of the allowed one-of property child elements.
In the
fill
element example at the beginning of this chapter, the
linear
,
pattern
,
radial
,
solid
and
stipple
elements are mutually-exclusive, having been identified as One-of properties.
Property Defaults
The processing application must supply defaults for properties omitted from an element, using the
following guidelines:
●
Regular properties. The processing application must provide the default values indicated in the
element descriptions in this specification.
One-of properties. The processing application must provide one of the properties as a default. That is,
the absence of any one-of child elements implies the application must provide a default.
●
Children
Elements in the Children category don't represent properties at all. They represent tangible objects that
often have the capability to contain each other and often are indeed called “containers”. Examples of such
children include the
field
and
subform
elements. A
subform
element has a variety of attributes and
child elements that represent the properties of the
subform
itself. Additionally, the
subform
may
enclose a number of child elements that express children of the subform, such as fields, draws, or other
subforms.
The distinction between child elements that are (structured) properties and those that are “true” children
is intentional. While all properties could be expressed as attributes, the attribute proliferation required to
describe a deep structure would be overwhelming. Property child elements tend to be singly occurring, or
occurring in known numbers (e.g., four edges in a border).
Element Occurrence
Singly Occurring Elements
Elements that are defined as singly occurring
[0..1]
are permitted to be defined only once within the scope
of the enclosing element. Unless stated otherwise all elements are singly occurring. Singly occurring
elements usually each represent a property of the enclosing element, rather than an object aggregated by