Reusing XML Processing Code in non-XML Applications

XML can be considered as a representation of hierarchical data, and the XML-related standards - as methods of processing such data. We describe benefits of XML view on legacy data and its processing, and suggest a method to develop XML tools and make them reusable for different tree-like structures in different programming languages.
Our approach is to use virtual machine technology, in particular, the Scheme programming language. We’re taking the unusual step of using the Scheme syntax itself as a native virtual machine language. Together with the SXML format and Scheme implementations tuning, it gives us the XML virtual machine (XML VM).
Reference implementations are ready for the Python and C languages. We describe a library for XSLT-like transformations of the Python parse trees and a special version of the GNU find utility which supports XPath queries over the file system.

The basis of some applications is hierarchical data structures plus methods of processing the data. Possible examples are compilers, interpreters and text processors. The former two may use abstract syntax trees (ASTs) to represent results of parsing a program and some other trees to deal with code transformations. Text processors may use trees to represent the structure or the formatting properties of a document.
Although the applications are from different domains, the basic operations on trees are the same. For example, getting list of children is a standard functionality for any tree. Some more advanced operations (for example, getting children with filtering) are also common. The problem is that possibly complex code for the advanced operations should be written and being updated for all the tree models, so maintenance become nightmare.
The possible solution for elimination of code duplication is to unify the tree models. As XML is now extremely popular, it’s reasonable to choose XML as an universal representation for trees. For needs of our work, the most fruitful feature of XML is existence of XML-related standards which in fact are design patterns for tree processing. And one of the most useful standards is XPath. In this paper, we give examples of XML and XPath and discuss benefits of seamless use of XML tools in legacy applications.

Read more on: http://uucode.com/texts/genxml/genxml.html