Microsoft Transaction Server COM

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Microsoft Transaction ServerCOM

• Jim LyonHPTS 99

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COM Overview

• Original goal allow code from different
  organizations to cooperate inside a process.
• Different compilers.
• Different languages.
• Different release schedules.
• Wildly successful
• Introduced circa 1990.
• Underlies OLE.
• 1billion market in third-party objects.
• On every windows system, and some others.

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COM Overview

• Basic concept interface pointer
• Expresses function signature contract and some
  semantics.
• Similar to Java interface.
• Each object implements 1 or more interfaces.
• Dynamically discoverable.
• Single inheritance of interface definitions.

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COM Overview

• COM is a binary, runtime standard
• Interface pointer a pointer to a pointer to an
  array of pointers to functions.
• Completely neutral to language or runtime
  environment.
• Supported from C, C, VB, Cobol, Java, and
  various interpreters, and a host of third-party
  environments.

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COM Evolution

• Distributed COM (1995)
• Put clients and servers on different machines,
  via proxy/stub technology.
• MTS (1996, 1998), COM (2000)
• Add declarative behavior to server objects.

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MTS, COM

• Goal Make it easy to create OLTP applications.
• Design points
• Allow programmer to think serially
• Leave the multithreading to us
• Get system services declaratively.

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MTS Services

• Security (access control, auditing)
• Serialization
• Transactions
• Object lifetime
• Others
• Model largely copied by EJB.

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MTS is Winning
Does your organization use MTS?
Project Phases
Yes (85)
No (15)
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Success FactorYour Choice of Languages
Programmer Population
Language Use with MTS
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Other Success Factors

• Microsoft is focused on making it work.
• Consortia are frequently focused on
• Getting a spec published.
• Ensuring that no competitor gets an advantage.
• Trying to fight a common enemy.
• Religion (write once, debug everywhere)

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Other Success Factors

• Integration
• Push the ORB into the OS.
• Push the Web Server into the OS.
• Evolution
• Every large system that works has evolved from a
  small system that worked. (Fred Brooks)