Notes on core issues in the Choreology Contribution Alastair Green Choreology Ltd OASIS WSTX Technic

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Notes on core issues in the Choreology
ContributionAlastair GreenChoreology LtdOASIS
WS-TX Technical CommitteInaugural Meeting,
Cupertino, Calif., November 16-17, 2005
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Three things

• Out-of-scope all Choreology issues that are a
  simple matter of editorializing, raw bug fixes
  etc, derivative of core issues
• Making sure WS-BA fulfils its stated purpose well
  and economically
• Two coordination protocols or one?
• Fault on Close supporting compensation-based
  business transactions, delivering the
  specification model requirements
• Selective outcome (mixed outcome) and composition

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Background

• Dr Peter Furniss, past editor of CCR, past editor
  of OSI/TP, editor and primary author of BTP
• Alastair Green, co-author of BTP
• Working on JSR156 (Java API for XML Transactions)
• Last five years working on business transaction
  management
• implementing BTP, WS-AT and WS-BA in product
• participated along with IONA, Arjuna, IBM and
  Microsoft in interop tests
• Some interesting customer cases

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OASIS Business Transaction Protocol

• Committee Spec 1.0, June 2002, 1.1 2004
• The first cut, very early in the life of Web
  Services
• No WS-Addressing, no WS-Policy, no WS-Secur etc
• The death of BTP, unlike that of Mark Twain, was
  always greatly understated
• However, there is a memetic strain much of value
  was achieved
• Cohesive transactions (business rules rule)
• Respect for participant autonomy
• Support for any application contract and endpoint
  behaviour

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What are compensations, and why use them?

• Compensations seem to date back to System-R
• Oft-cited paper by Irving Traiger,1983
  (little-read, I suspect)
• Gray and Reuter Chapter 4 discusses
• Multi-level transactions
• Open nested transactions
• Compensations also arise later in discussions of
  workflow (e.g. Roller König, Production
  Workflow)
• Original aim to preserve isolation while
  increasing concurrency
• Coordinating and structuring use of independent
  atomic actions (e.g. technical transactions on a
  database)
• Highly-constrained usage to ensure isolation
• If constraints are relaxed then we enter a
  different world

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The canonical case optimizing concurrency with
interleaving

• Original aim to preserve isolation while
  increasing concurrency
• Essence of original compensations strategy is to
  use independent atomic actions in a nested
  structure to create an isolated overall atomic
  action
• Locks are applied implicitly by ordering of
  actions using an object hierarchy
• Partial effects do not escape
• Read access must traverse root-to-leaf paths
• None of these conditions can be assumed with BPEL
  or any other service composition ? application
  concurrency control ? transparent locking

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Le rouge et le noir (Red or Black)

• A novel by Stendhal which examines provincial
  society in restorationist France, in the
  aftermath of Napoleon
• Near-50 probable outcomes in roulette
• The colour scheme of these slides
• A diagramming convention for business protocols
  and coordination protocols
• None of the above
• All of the above

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WS-BA model requirement processing a quote
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WS-BA model requirement tentative claim on
resources

• Credit authorization service
• Reserve, drawdown/replenish
• Multiple levels of authorization (counterparty,
  country, industry sector, cross-border)
• A composite service, with a contingent interface
• Requires Provisional-Final model

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Provisional-final contingent operation
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Do-compensate contingent operation
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Validate-do contingent operation
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WS-BA modification required to support all three
patterns
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Selective outcome issues

• Loose-coupling and composition violations
• Policy assertions distinguishing Mixed and
  Atomic
• Lack of globally unambiguous participant
  identifiers
• Inadequate specification
• Lack of globally unambiguous participant
  identifiers
• No rule of Atomic cancellation on participant
  fault
• Over specification
• Statements re mandatory and optional behaviour