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Connect Systems With Indigo
Indigo is meant to be the service-oriented successor to ASMX Web services, Web Services Enhancements (WSE), .NET Remoting, and other technologies.
by Roger Jennings

Tech•Ed, June 8, 2005

Windows Web service developers have their work cut out for the next month or two. For starters, Microsoft launched on May 25, 2005 an RC for the Beta 1 version of an Avalon/Indigo runtime for Windows XP SP-2 or Windows Server 2003 and an accompanying WinFX SDK that's compatible with VS 2005 Beta 2. About a week later, MSDN posted the June Community Technical Preview (CTP) of Web Services Enhancements (WSE) 3.0 for Visual Studio 2005 Beta 2 and related hands-on labs (see Resources). The WinFX Beta 1 SDK includes a set of C# and VB Indigo console projects in \Program Files\Microsoft SDKs\WinFX\samples\AllSamples.zip. WSE 3.0 CTP includes C# QuickStart samples only, VB versions of the WSE 3.0 hands-on labs for messaging and security features also are missing, as expected.

Microsoft designed WSE 3.0 and Indigo to support its Connected Systems vision that Paul Flessner addressed in his Tuesday keynote session. (Also see the Microsoft Web Services DevChannel and FTP's extensive video coverage of Indigo Day at VSLive! San Francisco in February.) A quick search of Tech•Ed 2005 sessions returned 18 hits for WSE as the keyword and 10 for Indigo in the Connected Systems Infrastructure track. According to Microsoft's "Connected Systems for Developers" PowerPoint presentation, Connected Systems share these five objectives:

1. Connect information workers with computing infrastructure
2. Evolve distributed systems to reflect the real world
3. Span boundaries without a single owner of the entire system
4. Provide Web services fabric and contracts
5. Leverage existing investments; use service orientation for future systems

WSE 3.0/VS 2005 and ASP.NET 2.0/IIS 6.0 (ASMX) provide the infrastructure for today's Web services and Windows 9x, 2000, and XP clients. As Indigo for Windows Server 2003 and Windows XP SP-2 nears RTM, developers should consider upgrading their Web services fabric and contracts to Indigo, even at the expense of discontinuing support for clients running Windows 9x and 2000. Why the Connected Systems objectives suggest using "service orientation for future systems" is a mystery. Microsoft has been touting service orientation (SO) and service-oriented architecture (SOA) almost as long as XML Web services.

Microsoft's four tenets of service orientation and, by inference, SOA are:

1. Boundaries are explicit
2. Services are autonomous
3. Share schema and contract, not class
4. Service compatibility is based on policy

Paul Flessner and Pat Helland discussed explicit boundaries and autonomous services at Tech•Ed 2002 in conjunction with Microsoft's ill-fated Global XML Architecture (GXA, see Resources). Don Box's promise that a GXA toolkit would arrive "within our lifetime" hasn't been—and clearly won't be—fulfilled. GXA has been subsumed by today's WSE, document/literal messaging, WSDL, and Indigo's future data contracts to enable sharing schema and contracts.

Data contracts, which correspond to WSDL's XML schema, let you annotate classes to expose specific members and hide implementation details. Indigo automatically generates policy based on Web service code or declarative configuration files. Clients retrieve the policy and configure themselves to meet the service's requirements.

Microsoft describes WSE as "an engine for applying advanced Web service protocols to SOAP messages," which writes "headers to outbound SOAP messages and read[s] headers from inbound SOAP messages" by applying a chain of output and input filters. WSE also modifies the SOAP message body by, for instances, encryption or description. WSE 3.0 is a fully supported add-in for VS 2005 that Microsoft's Mark Fussell promises to release within two to four weeks of .NET Framework/VS 2005 RTM. In the meantime, the WSE 3.0 team plans monthly CTP drops.