Outline for Handling XML Documents
In the second phase, the application applies the business logic. This entails
actually processing the input information retrieved from the XML document.
Such processing is considered document centric when the logic handles the docu
ment directly, or object centric when the logic is applied to domain specific
objects to which the retrieved information has been mapped. As a result of this
processing, the application may generate XML output information, which is the
The steps for this third phase, XML output processing, mirror that of XML
input processing. Producing XML output consists of the following steps:
Assemble the document
Assemble the output document from the results of
applying the application's logic.
Transform the document
If necessary, transform the document from the in
ternally supported schema to the appropriate external vertical schemas.
Optionally validate, then serialize, the document
Validating prior to seri
alizing the output document is often considered optional.
It is quite possible that an XML based application may only implement some
of these phases, generally those that apply to its services. For example, some
applications use XML just for configuration purposes, and these applications may
only consume XML documents. Other applications just generate device targeted
content, and these applications may only produce XML documents (Wireless
Markup Language, HTML, SVG, and so forth). E commerce applications, on the
other hand, may both consume and produce XML documents.
There are also applications that specialize in particular operations, such as
those that specialize in transformations, in which case they perform only their
intended operations. For instance, an application's function might be to select and
apply a transformation to a document based on the processing requirements
passed with the document, thus producing one or more new documents. In this
example, the application's logic may consist only of the style sheet selection logic.
Developers implementing applications with a document centric processing
model where the business logic itself handles the documents may find that
document handling is more entangled with the business logic. In particular, the
steps that may intermingle with the business logic are those to disassemble the
consumed documents and assemble the output document. These cases require
careful handling. See Abstracting XML Processing from Application Logic on