Taverna Workbench 2.x has a GUI interface for Preferences (File > Preferences > HTTP Proxy), where various properties can be customised. HTTP proxy is one of them.
In Taverna Workbench 1.7.x, you can specify using a HTTP proxy by modifying your mygrid.properties and uncommenting and completing the lines referring to http.proxyhost and http.proxyPort. The mygrid.properties can be found in the conf/ directory of the Taverna startup directory. In an environment where Taverna is shared between users then this may be customised by an individual by copying and modifying the mygrid.properties in conf/ directory in the Taverna home directory.
If you require authentication you will also need to uncomment and modify the lines referring to http.proxyUser and http.proxyPassword.
If there are hosts that you wish to use that do not require using a proxy then you can add a similar line that declares http.nonProxyHosts.
This is documented in full in the Taverna manual – Proxy configuration.
