Chapter 4, Exchanging Data Between an External Application
and a Basic XFA Form
XFA Specification
Basic Data Binding to Produce the XFA Form DOM
155
being added to the Form DOM are not associated with any nodes in the Data DOM. By contrast if there is
no data description then the new structure in the Form DOM is based purely on the Template DOM.
Note:
The presence of a data description does not by itself guarantee that the Data DOM will conform to
the data description at the end of the data binding process. To ensure conformance after binding,
the data must start off conforming to, or being a subset of, the data description. In addition the
structure of merge-able nodes in the template must correspond to the data description or to a
super set of it. However these restrictions are not imposed or enforced by the data binding process.
It does not check for conformance and has no problem dealing with non-conforming data or
indeed with the absence of a data description.
Optionally, after all other processing on a record is complete, the data binding process may adjust the Data
DOM to make it exactly parallel the structure of the Form DOM. This forces the data into a shape imposed
by the template and the data description. Use of this option precludes round-tripping.
Data binding is also known as
merging
because it can be thought of as merging the data (and possibly
data description) with the template.
A variant known as an
empty merge
does not use data from the Data DOM. In this case, the Form DOM is
created based on the template and the data description. Optionally, default data matching the Form DOM
may be inserted into the Data DOM.
Conventions
Many drawings in this section depict relationships between nodes in tree graphs. Nodes are depicted
using different shapes and shadings, as shown in the following figure.
nam e
non-transparent subform
transparent subform
nam e
Form &
Template
DOMs
subform set
nam e
instance manager
Data
DOM
nam e
data group
nam e
“va lu e
”
data value
nam e
“va lu e
”
nam e
“va lu e
”
exclusion group
field
Key to node symbols