One of the problems I was dealing with recently was about how to build a communication medium between two systems running on two different platform,as an example imagine you have an online sales system, accounting systems and critical financial information are kept in an Oracle on a Solaris server with its all related management resources, On the other side you have the website running on MS IIS on a Windows 2000 or NT server,this can also be Apache on Linux/Windows, anyway the only data which is needed to be transferred between two systems are Purchase information and transactions,which you can call it generally business data.so the question is is there a secure/efficient/standard way to do so? I found the answer XML Messaging Protocols are best suited for this purpose specially SOAP with its very simple structure. After I read about that carefully I realized that no security issues were considered in SOAP implementation so I searched again and found this good article.
SOAP has two implementation one from Microsoft and one from IBM ,As you expect IBM version is more stable and is used to implement Apache's XML connectivity.