It's clearly a set of arguments (separated by ':') to a function, i.e. it's a RPC invocation. The first seems to be the session of congress, 113th and 107th. The second, perhaps the nth item in that collections? The third, a temporary filename, probably where the search result is stored, so you don't have to re-run the search which you hit "back". The last bit, probably a later addition that manages breadcrumb navigation.