Database Research Group (CIS)

Document Type

Conference Paper

Date of this Version

May 2001


Postprint version. Copyright ACM, 2001. This is the author's version of the work. It is posted here by permission of ACM for your personal use. Not for redistribution. The definitive version was published in Proceedings of the Fourth International Workshop on the Web and Databases (WebDB 2001), May 2001, pages 37-42.


ubQL is a distributed query language for programming large-scale distributed query systems such as resource sharing systems. The language is obtained by adding a small set of mobile process primitives (communication channels, migration operators, etc.) on top of any additional query language. Queries are encapsulated into processes and can migrate between sites thus enabling cooperation. An important methodological device is the separation of the installation (including migration) of query processes from the distributed execution of the queries.

In this paper, we give an overview of ubQL, show how to encode widely used distributed query patterns such as chaining, recruiting, query/data/hybrid shipping, etc., and evaluate some language based rewrite strategies for the installation of ubQL queries that use only partial and distributed knowledge of execution costs.



Date Posted: 07 June 2007

This document has been peer reviewed.