There is another category of plugin called the gateway category; this is intended for use as a service. There are two plugins currently shipping in that category: the Google Scholar plugin and the Resolver plugin. The best way to make an export plugin run as a service is to write a simple gateway plugin as a wrapper for it; look at the READMEs and the code in each gateway plugin's directory for more information.
Open Journal Systems Team
Don't miss the First International PKP Scholarly Publishing Conference
July 11 - 13, 2007, Vancouver, BC, Canada