Commitment Alignment: Semantics, Patterns, and Decision Procedures for Distributed Computing

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Title: Commitment Alignment: Semantics, Patterns, and Decision Procedures for Distributed Computing
Author: Chopra, Amit Khushwant
Advisors: Dr. Rada Chirkova, Committee Member
Dr. S. Purushothaman Iyer, Committee Member
Dr. Mladen A. Vouk, Committee Member
Dr. Munindar P. Singh, Committee Chair
Abstract: Current service-oriented architectures lack business-level software abstractions. As a result, service implementations are unnecessarily rigid. Commitment-Based SOA or CSOA, an agent-oriented approach to SOA, fills this gap. The key insight of CSOA is that commitments are crucial to realizing the full possibilities of engagement. In CSOA, each business service is modeled as an agent. CSOA gives primacy to the interactions among agents. Interactions have business meaning in terms of the commitments the agents have toward each other. This dissertation takes a distributed systems view of CSOA, where agents communicate using asynchronous messaging. A problem that arises in distributed settings is that of commitment misalignment: an agent comes to infer a commitment from another agent, but the other agent does not infer that commitment. A commitment misalignment precludes any possibility of successful engagement among agents. We formalize alignment under asynchronous messaging. We consider three causes of misalignments. (1) Autonomy: agents are free to send messages; in other words, they communicate asynchronously. (2) Distribution: in a distributed system, some agents would in general have more information than others. (3) Interface incompatibility: agents assign different meanings to messages. To address the first two causes, we propose a formalization of commitments that consists of three elements: a semantics of the commitment operations; messaging patterns that implement the commitment operations; and weak constraints on agents' behaviors to ensure the propagation of vital information. The constraints constitute additional messaging patterns that are critical to alignment. We prove that our formalization ensures that no misalignment arises because of autonomy and distribution. We illustrate the generality of our formalization with several real-life scenarios. To address interface incompatibility, we formulate a decision procedure that checks for interface compatibility, and prove its correctness.
Date: 2008-12-05
Degree: PhD
Discipline: Computer Science

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