Chapter 4 XML Processing

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fragment, and so forth from the incoming XML document and then pass these

individual fragments to the appropriate business process stages in an appropriate

format (DOM tree, Java object, serialized XML, and so forth) expected by the

receiver.

While it is complementary to most of the mapping design strategies presented

in  Mapping Design Strategies  on page 143, this technique is best compared

against the flexible mapping design strategy. (See  Flexible Mapping  on

page 148.) Flexible mapping advocates a decentralized mapping approach: Com 

ponents or stages in a workflow each handle the complete incoming document,

but each stage only processes the appropriate part of the document. Fragmenting

an incoming document can be viewed as a centralized implementation of the flex 

ible mapping design. Fragmenting an incoming document, by suppressing redun 

dant parsing of the incoming document and limiting the exchanges between stages

to the strictly relevant data, improves performance over a straightforward imple 

mentation of flexible mapping. However, it loses some flexibility because the

workflow dispatching logic is required to specifically know about (and therefore

depend on) the document fragments and formats expected by the different stages.

Fragmenting a document has the following benefits:

  It avoids extra processing and exchange of superfluous information throughout 

the workflow.

  It maximizes privacy because it limits sending sensitive information through 

the workflow.

  It centralizes some of the XML processing tasks of the workflow and therefore 

simplifies the overall implementation of the workflow.

  It provides greater flexibility to workflow error handling since each stage han 

dles only business logic related errors while the workflow dispatching logic 

handles document parsing and validation errors.

4.3.7 Abstracting XML Processing from Application Logic

As mentioned earlier, the developer of an XML based application and more specifi 

cally of a Web service application, may have to explicitly handle XML in the fol 

lowing layers of the application:

  In the interaction layer of a Web service in order to apply some pre  or post 

processing, such as XML validation and transformation to the exchanged doc