1. 1 Formal Models for Distributed Negotiations Description Roberto Bruni Dipartimento di Informatica Università di Pisa XVII Escuela de Ciencias Informaticas (ECI 2003), Buenos Aires, July 21-26 2003

2. Formal Models for Distributed Negotiations2 A Web as Wide as the World WAN / WEB / Global computing Asynchronous communication Dynamic interconnectivity of autonomous components Dynamic adaptation Interoperability (heterogeneous systems) Mobility Openness Security Quality of services Different levels of abstraction

3. Formal Models for Distributed Negotiations3 Our Focus In commercial applications, separately designed and implemented components must interact commit (intermediate) results of long-running activities upon (partial) agreements e.g. e-commerce, on-line auction systems Formal (meta)models should avoid ad-hoc proprietary solutions offer alternatives to centralized transaction managers hide the coordination layer (separation of concerns)

4. Formal Models for Distributed Negotiations4 Distributed Agreements Data integration unstructured documents in different formats Process cooperation coordination / orchestration / choreography different platforms and policies Negotiations / Contracts commit, abort, compensation hierarchical decisions dynamic membership fully distributed control

5. Formal Models for Distributed Negotiations5 Commitment Different concepts in different areas Classical DataBase transactions Transactional Workflows Committed choice languages (e.g. AKL) Emerging Transition synchronization PDL with commit primitives

6. Formal Models for Distributed Negotiations6 Roadmap I DataBase Transactions ACID, serializability, commit, abort, roll-back One, no-one, one-hundred-thousand transactions Flat Savepoints Chained Nested Distributed Relaxation for mobile computing Multi-level Sagas Split Flexible Multi-transactions

7. Formal Models for Distributed Negotiations7 Roadmap II Commit protocols Transaction managers, failures, timeouts, recovery Generic atomic commitment protocol Two-Phase Commit (2PC) protocol Decentralized 2PC Linear (nested) 2PC Three-Phase Commit protocol

8. Formal Models for Distributed Negotiations8 Roadmap III Concurrent models Petri Nets (PN) Terminology: places, transitions, tokens, markings Semantics: firings, reachability, processes, unfolding Token philosophies Zero-Safe Nets (ZSN) Transition synchronization Abstract and refined nets Interpreter via unfolding

9. Formal Models for Distributed Negotiations9 Roadmap IV A Simple Process Algebra (SPA) Signature Operational semantics (LTS, SOS rules) Abstract semantics (behavioural equivalences) Encoding SPA in ZSN Compositional encoding True concurrent semantics Correspondence theorem

10. Formal Models for Distributed Negotiations10 Roadmap V Coordination Linda paradigm PA for Linda primitives Ordered / Unordered semantics Expressiveness Linda with transactions (TraLinda) Contextual ZSN Serializability in JavaSpaces create/commit primitives informal comparison with TraLinda

11. Formal Models for Distributed Negotiations11 Roadmap VI From PN to join-calculus Coloured PN Reconfigurable PN Dynamic PN = join-calculus Operational semantics Orchestrating transactions in join-calculus Centralized encoding of ZSN Distributed encoding of ZSN Distributed 2PC

12. Formal Models for Distributed Negotiations12 Roadmap VII Microsoft © BizTalk short / long / timed transactions Extending and executing short transactions via ZSN A calculus of compensations for long transactions An algebra of LRT Committed join-calculus Membranes, boards and compensations 2PC in the pi-calculus Extending the pi-calculus