Short Running Title: Wcl: a Co-ordination Language for Geographically Distributed Agents Wcl: a Co-ordination Language for Geographically Distributed Agents A. Rowstron, Wcl: a Co-ordination Language for Geographically Distributed Agents

In this paper a tuple space based co-ordination language, and a run-time system which supports it is described. The co-ordination language is called WCL, and it is designed to support agent co-ordination over the Internet between agents which are geographically distributed. WCL uses tuple spaces as used in Linda. WCL provides a richer set of primitives that traditional tuple space based systems, and provides asynchronous and synchronous tuple space access, bulk tuple primitives, and streaming primitives which, as a whole, provide a complete framework more suited to co-ordination over the Internet compared with the Linda primitives. The primitives emphasise e ciency and location transparency (of data and agents) and this is exploited in the current run-time system used to support WCL. The run-time system is described in the papers and is distributed and uses the location transparency and dynamic analysis of tuple space usage to migrate tuple spaces around the distributed system. Some initial experimental results are given which demonstrate the performance gains of using the tuple space migration. The paper motivates the inclusion of many of the primitives, and demonstrates how a well designed set of primitives provides performance and e ciency. The JavaSpace primitives are used as an example of how the choice of primitives can detrimentally e ect the e ciency of the language, and exclude required co-ordination constructs. ii A. Rowstron, WCL: A Co-ordination Language for Geographically Distributed Agents 1