A partial implementation of the W3C's XML Pipeline Language (XProc) . Choosing to implement an XProc processor in XSLT means there are some features that it will not be possible to support in pure XSLT, hence the name 'half-pipe'. On the flip-side though, using XSLT to compile an 'executable' XSLT transform that will carry-out the steps defined in the XML pipeline definition allows you to work on the same level as both the pipeline definition and the XML data it is processing.

Using XSLT requires a transformation engine, and in this case half-pipe uses Saxon 9. There are some useful extensions provided by Saxon that make implementation easier than it would otherwise be.