http://blogs.msdn.com/drnick/archive/2008/08/05/system-types-in-metadata.aspxIt's bad practice to use system types when defining an operation contract. A system type is often a complex composition of primitive types that has no direct analog in other implementations. By using a system type, you bind your service to the particularenCommunityServer 2.1 SP1 (Build: 61025.2)http://blogs.msdn.com/drnick/archive/2008/08/05/system-types-in-metadata.aspx#8836311Wed, 06 Aug 2008 09:47:38 GMT91d46819-8472-40ad-a661-2c78acb4018c:8836311Nicholas Allen's Indigo Blog<p>The address filter mode that we looked at last time solved the problem of funneling all of the messages</p> http://blogs.msdn.com/drnick/archive/2008/08/05/system-types-in-metadata.aspx#8845208Sat, 09 Aug 2008 21:55:51 GMT91d46819-8472-40ad-a661-2c78acb4018c:8845208Tanveer Badar<p>An inaccurate heuristic would be to filter anything residing in a namespace beginning with System., MS. or Microsoft. prefix.</p>