Transformation-by-Example for XML

xml is a language for describing markup languages for structured data. A growing number of applications that process xml documents are transformers, i.e., programs that convert documents between xml languages. Unfortunately, the current proposals for transformers are complex general-purpose languages, which will be unappealing as the xml user base broadens and thus decreases in technical sophistication. We have designed and implemented xt3d, a highly declarative xml specification language. It demands little more from users than a knowledge of the expected input and desired output. We illustrate the power of xt3d with several examples, including one reminiscent of polytypic programming that greatly simplifies the import of xml values into general-purpose languages. 1 XML and Transformations xml [3] is a simplified version of the markup description language sgml. Because of xml’s syntactic simplicity, it is easy to implement rudimentary xml processors and embed them in a variety of devices. As a result, a wide variety of applications are adopting xml as a data representation standard. Declarative programming languages must therefore provide support for xml. They can do better; as this paper demonstrates, ideas from declarative programming can strongly enhance the toolkit that supports xml. Syntactically, xml has a structure similar to other sgml-style markup languages such as html. The difference between xml and a language like html is that xml really represents a family of languages. Concretely, xml provides two levels of specification: – An xml element defines a tree-structured representation of terms. This representation is rich enough to express a wide variety of data. A sample element, which might represent information about music albums, is A043CD BD34LP