XFA Specification
Chapter 19, Data Description Specification
Data Description Element Reference
754
xsi
On output null nodes are represented by empty elements with the attribute
xsi:nil
equal to
true, as defined in XML Schema [XMLSchema]. On input any element (empty or not) with
xsi:nil="true"
is mapped to a null node, while empty elements that do not have
xsi:nil="true"
are mapped to regular nodes with values of the empty string.
Note:
This applies only to elements. Attributes with the value of empty string are governed by the
dd:reqAttrs
attribute.
dd:reqAttrs Attribute
This attribute lists the names of mandatory attributes for the element. The names in the list are separated
by white space. The order of the names is not significant. Each name in the list must match the name
(including namespace) of an attribute on the element. If an attribute name in the list has no namespace
prefix it is imputed to inherit the namespace of the element, just as it does when used in the instance
document.
On input an attribute with the value of empty string is treated the same way as any other attribute. On
output, when an attribute is mandatory but the attribute is not present in the DOM, the XFA application
generates an attribute with the value of the empty string. By contrast when the attribute is not mandatory
and it is not present in the DOM it is omitted from the XML document.
For example, the following fragment declares that in the “shirt” element the attributes “color” and “size”
are mandatory, but “supplier” is optional. All of the attributes inherit the namespace of their element.
<t:shirt color="" supplier="" size="" dd:reqattrs="size color"/>
The following example declares two mandatory attributes. The element is in the default namespace. One
of its mandatory attributes is also in the default namespace, but the other is in a different namespace.
<animal name="" vet:species=""
dd:reqattrs="name vet:species"/>