WAQL Preprocessor for Java (WAQL-PP)

This page is about the WAQL Preprocessor for Java, an experimental implementation capable of parsing and transforming WAQL queries. The key idea of WAQL is that it provides a convenience syntax for XQuery, which otherwise tends to become complex and hardly comprehensible in bigger scenarios. WAQL queries are transformed into valid XQuery expressions, which are finally executed by a third-party XQuery engine.

The key characteristics of this implementation are that it is very lightweight, safe to use in multi-threaded environments, developed as an open source project and licensed under the Apache License, Version 2.0 which supports collaborative development.


There is some documentation available on how to use this preprocessor, please look through the following list to see if your questions are already covered. In case you are missing something feel free to contact me.

  • For first time visitors the How to use WAQL-PP guide might be a good starting point to get to know the preprocessor and it’s architecture. It contains some common usage examples and a description of the API provided by the library.
  • If you already know the basics and just need a reference the latest online API documentation in the usual Javadoc format is of great use. It is also available as a separate package for offline usage as a download with each release in the download section below.
  • In case you are interested in the preprocessor internals the How to hack on WAQL-PP guide is what you are looking for. It describes the implementation so that you can easily start off with customizing or contributing to the project.


The version waqlpp-0.1 is the latest release of the WAQL preprocessor. Below is a list of all packages available with this release, please see the release notes for more information about this version. You can also download previous versions by visiting the download directory directly.

Package-File: Checksums: Package-Size: Release-Date:
waqlpp-0.1.jar [md5] [sha1] 108 kB 2010-11-11
waqlpp-0.1-doc.zip [md5] [sha1] 32 kB 2010-11-11
waqlpp-0.1-src.zip [md5] [sha1] 871 kB 2010-11-11


The following is a list of interesting references to offsite material about WAQL or WS-Aggregation in general. If you know about related links that are missing from this list, just let me know so I can add them.

  • Primary focus of this project was to establish a preprocessor which can be used as a component in the WS-Aggregation framework developed by the Distributed Systems Group at the Vienna University of Technology.
  • The paper that first introduced WAQL as a specialized query language is WS-Aggregation: Distributed Aggregation of Web Services Data and will appear at the 26th ACM SIGAPP Symposium On Applied Computing (SAC).
  • The specification which this implementation is based on is XQuery 1.0 as recommended by the W3C on the 23rd of January 2007. Extensions specified as part of XQuery 1.1 are not yet incorporated, but might be at some later point.