Daniel Fötsch, Uni Leipzig: Operator hierarchy concept for XML transformation
Daniel reviews transformation methods for XML. You can do it on the plain text level with regular expressions etc, with APIs like DOM and SAX, with specialized languages like XSLT, STX, XUL and XUpdate. He talks about this last category.
The idea behind “operator hierarchies” is to create low-level transformation files automatically from high-level transformation files. You can write transformations on a higher level of abstraction, which makes the transformation file shorter and more readable and maintainable. Then it’s transformed through an “operator file”, and expanded into a low-level transformation file. In fact, you can have several levels of this operator expansion, starting with domain-specific operators, then generic operators, then low-level operators.
So you could have something like this:
.(much XML)
<isif condition="...">
... (XML) ...
<iselse/>
... (XML) ...
</isif>
(more XML)
And this could be expanded to a much longer XSLT fragment.
Mostly it’s about avoiding repetition in XSLT files by factoring out common code.