Abu Obeida and Mike Champion from Microsoft announced recently the below articles. I recommend this reading for those of you who need to write interoperable web services. Of course not each article is relevant for each interop scenario so guess what? I've read them for you so you can decide which ones are relevant for you.
Christian Weyer and Buddhike de Silva have listed most types you might ever want to use with web services and verified their interoperability status. This is a must read for every public facing web service developer.
One thing that I am missing here though is the Axis2 java stack which is very popular. Also I'm confused by the check on WebSphere - as an application server you can use various stacks on it so I'm not sure which one was used. I assume Wcf was used on the .Net side (".Net 4" is specified) and I'm very curious if the data contract was able to cope with all scenarios or was xml serialization required in some cases. Generally data contract are optimized to enforce "best practice" which is sometimes counterproductive for interoperability.
The conclusion is very promising - good interoperability exists in almost all scenarios. One important reminder is the lack of interoperability with Hashtable and some of the generic types.
Jesus Rodriguez wrote a great article on ws-security interop between Wcf and Oracle WebLogic. Naturally the article dives into the ws-security details and is very technical. It proves that X.509 message security is a good option for interoperability. While jesus shows how to achieve federation interoperability via SAML and WS-Trust, it is clear that there is still a way to go here as a holder-of-key scenario is still not possible. I have not tested it myself but hopefully bearer tokens should also work well with these parties. The article does not mention it as it deals with message security while bearer tokens are a mix of message and transport.
Jesus adds another good one and this time on interoperability between Wcf and WebSphere. The username and x.509 scenarios work pretty well. The article mentions that WS-Trust interoperability is possible, but does not give the details, so I'm not sure if it is a mistake in the upload or if it really required some tweaks which were out of scope. Either way this is yet another proof that there is still a way to go with federation interoperability. Such security scheme will be very popular in the cloud era so hopefully all vendors will keep investing in it. As it stands now Wcf+Wif have great support for the related scenarios so I'll report on any news from the other vendors.
As a side note, While MTOM interoperability is possible here, I have seen in the past a few gotchas so hopefully a future paper will cover that up (I'll try to write about it myself actually).
A rich set of scenarios are working in this case, including security and MTOM. It is a little disappointing that a basic scenario like custom headers only partially pass, but NetWeaver is an opinionated framework that expose its users only what is relevant for them.
The combination of Metro and Wcf shows off the richest set of working interoperability scenarios. This is not surprising considering the fact that one of the goals of WSIT (Metro's security stack) is interoperability with Wcf.
To conclude, all articles are very interesting and show that interoperability is a reality.