To use Taverna remotely, you need a Taverna Server, which receives workflows for execution, executes them and makes the results available for collection.
You may also implement a simple server on your own by wrapping the Taverna Command Line Tool. A similar thing was done by the Taverna Server and the caGrid Remote Execution plugin.
You also need some sort of a client, which will enable you to submit the workflows for execution to the Server. This could be a Web-based client (such as a portal or a Web app) or a standalone client (such as the remote execution plugin for the Taverna Workbench 1.7.x).
Check out some examples on the portal work (i.e. invoking workflows remotely from a Web page), in particular the NeISS and the MetWare projects.
Taverna can also be used on grids and clouds. Check the FAQ as well.
