1. A system for enabling a business process engine to invoke a web browser as a web service server, the system comprising one or more computers configured to implement: a communication server coupled to a communication network to send information to and receive information from a web browser; a business process engine configured to implement at least one business process comprising a plurality of activities, the business process engine configured to send web service requests in a web service format and to receive web service responses in the web service format; a plurality of page templates predefined in accordance with the activities of the business process; and a servlet configured to: receive, from the business process engine, a particular web service request that is associated with a particular activity of the business process and that is intended for the web browser; determine a particular page template that is associated with the particular activity; cause the particular web service request to be converted, in accordance with the particular page template, from the web service format into a particular web page that is in a web page format that can be processed by the web browser; cause the particular web page to be sent by the communication server to the web browser; receive, via the communication server, a response from the web browser; convert the response into a particular web service response that is in the web service format; and provide the particular web service response to the business process engine as a response to the particular web service request, thereby, enabling the business process engine to invoke the web browser as a web service server.