XFA Specification
Chapter 3, Object Models in XFA
Document Object Models
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The XFA DOM is not directly loaded from or written to XML, but some of the DOMs within it are. Within an
XFA application the XFA DOM always exists, even when none of the other DOMs do (for example, at the
start of processing).
The XFA Data DOM
The XFA Data DOM presents an abstract view of the XML data document. In this abstract view the
document contents are represented by two types of nodes, data group nodes and data value nodes. Data
group nodes represent grouping elements. Data value nodes represent non-grouping elements and
attributes.
There are property nodes in the XFA Data DOM. However usually these do not represent elements or
attributes in the XML data document. Rather they hold properties associated with an element or attribute.
For example, each node has a
name
property which holds the start tag of the element or the name of the
attribute. Similarly there is
namespace
property which holds the full namespace of the element or
attribute, regardless of whether it was inherited or declared explicitly. Sometimes a property node does
correspond to a particular attribute but in such cases the attribute is in a reserved namespace and is
treated as out-of-band information. For example, the
xsi:nil
attribute defined by [XML-Schema] in the
namespace
http://www.w3.org/2001/XMLSchema-instance
is
not
represented in the XFA Data
DOM as a data value node. Instead it modifies the
isNull
property of the data value node corresponding
to the element which holds it.
There are a large number of options available to transform the data on its way in from the XML Data DOM
to the XFA Data DOM. In most cases the reverse transform is applied on the way out. Hence scripts which
operate on the XFA Data DOM can be isolated from details of the XML representation. For example, it is
possible to rename particular elements or attributes on the way in. When the data is subsequently written
out to a new XML document the original element tags appear in the new document.
The XFA Data DOM is not directly loaded from or written to XML. However its content is echoed in the XML
Data DOM which is always loaded from and/or written to XML. Unlike most other DOMs, the XFA Data
DOM may operate in record mode. In this mode only global data plus a window of record data is resident
in memory at any moment.
Note:
Throughout this specification when the term Data DOM is used without specifying the XML Data
DOM or the XFA Data DOM, the XFA Data DOM is implied.
The XML Data DOM
The XML Data DOM is a standard XML DOM that is used to hold the content of the XML data document. In
accordance with the W3C XML DOM specification
[XMLDOM2]
attributes, and content. It does not distinguish properties from children nor does it ignore whitespace in
grouping elements. XFA processors do not in general operate directly on the XML Data DOM. Instead they
operate on the XFA Data DOM which presents and manipulates the same data in a more abstract way.
The XML Data DOM is always loaded from and/or written to XML. It has no other purpose. Unlike most
other DOMs, the XML Data DOM may operate in record mode. In this mode only global data plus a window
of record data is resident in memory at any moment.
Note:
Throughout this specification when the term Data DOM is used without specifying the XML Data
DOM or the XFA Data DOM, the XFA Data DOM is implied,
not
the XML Data DOM.