As part of GXA, Microsoft has defines a SOAP Extension specification called WS-Routing which does provides a mechanism to specify a message path in a SOAP header. But keep in mind that you may not need to specify the complete message path in your SOAP message. Your intermediaries may be smart enough (and in fact it may be there purpose) to figure out where to forward the message to. For example, an intermediary might do content-based routing of messages.
Obviously the architecture supports intermediaries. But perhaps you meant to ask whether or not any SOAP implementations support intermediaries? I don't think very many of the various SOAP implementations support the WS-Routing specification. I believe that Microsoft's and IBM's advanced WSTK tools provide support for WS-Routing. They both support the IBM/MSFT/Verisign WS-Security specification, which relies on WS-Routing. (The forthcoming standard OASIS WSS specification will not rely on WS-Routing, though, since it isn't a standard.)
But as I said, you don't need to specify the message path in your message. Almost all of the Web services management products are implemented as intermediaries, including products by Actional, AmberPoint, Blue Titan, Confluent, Digital Evolution, Flamenco, Grand Central, Infravio, Kenamea, Mindreef, Primordial, Reactivity, Talking Blocks, Vordel, WestBridge, and WestGlobal. When using these products, generally you target your SOAP message to the intermediary, and the intermediary determines where to send the message next.
This was first published in November 2002