xmlhack: XML Pipeline Definition Language introduced as Note

The W3C has released XML Pipeline Definition Language, which describes "the processing relationships between XML resources" as a Note.

Pipelining has been a popular term lately in XML discussions, with initiatives like XPipe and DSDL building models for how to pass XML between different kinds of processing. The Note focuses on particular set of issues managed by a single controller:

"A pipeline document specifies the inputs and outputs to XML processes and a pipeline controller uses this document to figure out the chain of processing that must be executed in order to get a particular result."

The syntax of the pipeline language owes a good deal to tools like make and Ant. The Process Classification section defines categories of processing that can be controlled: constructive, augmenting, inspection, extraction, and packaging.

Pipeline definitions might prove to be useful in conjunction with RDDL providing more detail than RDDL about how different parts interact. In some ways this specification is similar to XML Processing Description Language (XPDL), a long-obsolete proposal written by the author of this article. RDDL and this Note represent different pieces of the problem XPDL tried to solve (and assume the initial XML parse is complete), and each solves their piece more completely than did XPDL.

In some ways this may represent the return of the banished SGML declaration, but the use cases and example suggest that this may be quite reasonable.