C hapter 1s Beyond the Web Services Hype section concludes that enterprise application integration (EAI) projects will be the first major market for XML Web services. The theory is that XML, XSD, SOAP, WSDL, and HTTP[S] will pave the way to standards-based data interchange between information islands in a sea of disparate operating systems. Its common for multinational corporations to have divisions and subsidiaries that run five or more different relational database management systems under UNIX, Windows, and, increasingly, Linux operating systems. A uniform, standards-based system for secure information exchange over the Internet promises a substantial reduction of EAI development cost, longer lifetime for completed EAI projects, and decreased telecommunication expenses. The reality is that achieving EAI nirvana with XML Web services requires a substantial amount of upfront investment in developer training and establishing internal standards for SOAP message schemas. Integration of third-party XML Web services and schemas for SOAP XML message payloads generates additional complication and expense. Visual Studio .NETs Web Reference feature makes creating SOAP client proxies for ASP.NET XML Web services easy. IBMs WebSphere Studio Application Developer software includes Java XML tools and support for creating XML Web services. Cooperation between Microsoft and IBM in the development of the SOAP and WSDL specifications should result in few, if any, interoperability problems with XML Web services created with these two development tools. There are many other client- and server-side SOAP implementations in varying stages of development. The probability is about zero that Visual Studio .NET service consumers will interoperate with all SOAP implementations. By the time SOAP 1.2 and WSDL 1.2 become candidate recommendations, its a good bet that most commercial rpc/encoded Web services will interoperate at the version 1.1 level. The outlook is not as clear for document/literal SOAP implementations. TIP For an interesting comparison between the Microsoft and IBM approaches to XML Web service development tools, read the How IBM WebSphere Studio Application Developer Compares with Microsoft Visual Studio .NET white paper at http://www7b.boulder.ibm.com/wsdd/techjournal/0202_kraft/kraft.html. Standardizing Web Service Interoperability Web services are based on standards, but that doesnt mean that a Web service created with a Java- or Perl-based SOAP implementation will interoperate correctlyor at allwith a Visual Studio .NET client proxy. For example, the Alan Bush Compositions Web Service at http://www.alanbushtrust.org.uk/ soap/compositions.wsdl doesnt pass the Add Web Reference dialogs tests. The Add Reference button is disabled and the Available References page states, No Web References were found on this page. This behavior was probably caused by the developers use of an early version of the Microsoft SOAP Toolkit to create the WSDL file, which contains an xmlns:stk= http://schemas.microsoft.com/soap-toolkit/wsdl-extension namespace declaration. (See Figure 12-1.) 4 3 4 V  i  s  u  a  l B  a  s  i  c .  N  E  T X  M  L W  e  b S  e  r  v  i  c  e  s D  e  v  e  l  o  p  e  r    s G  u  i  d  e