OpenEdge Development: Working with XML - Product ...

Developing with XML in OpenEdge
Developing XML-enabled ABL applications with DOM
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The Document Object Model (DOM) is the original application programming interface (API)
for XML documents, as defined by the W3C. It continues to be the W3C recommendation for
XML parsing.
You use the DOM API to build a hierarchical tree structure that persists in memory and
represents your entire XML document. With this API, you can call the parser to build such a
tree for you in memory from an XML document. The DOM tree is then available for you to
easily manipulate using standard tree-traversal logic. For example, an XML document may
represent a list of address changes generated from a self-service Web site. Your application
might need to load the XML document into a DOM tree, perform some logical validation on the
data, and only then use the data to update customer address records in your database.
You could also use the API to programmatically build a DOM tree in memory and then write
that tree out as an XML document. For example, you may need to generate a list of customer
address changes for a business partner.
DOM advantages
The general advantages of DOM include:
• Data persists in memory
• You can go forwards and backwards in the tree (random access)
• You can make changes directly to the tree in memory
DOM limits
The general limits of DOM include:
• The entire document must be parsed before the tree is available to the application.
• You cannot load a subset of the document.
• Because the whole tree must exist in memory, it may not be suitable for handling very
large XML documents.
• A single error in the XML file may prevent the document from being loaded. This limit
makes DOM less attractive for use cases where XML is being retrieved in a stream rather
than as a static document.