Browsing by Author "Dr. Munindar P. Singh, Committee Chair"

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Bootstrapping Referral Systems With Social Network Information
(2007-05-16) Batalagundu Viswanathan, Arvind; Dr. Edward Gehringer, Committee Member; Dr. Laurie Williams, Committee Member; Dr. Munindar P. Singh, Committee Chair
This thesis addresses the challenge of facilitating human interactions in solving problems. To this end, it assigns an agent to each user, and models a social network as a multiagent system. A user's agent helps them by sending out and responding to queries on their behalf. Each agent makes its decisions based on its models of the expertise and trustworthiness of other agents. However, such models are not trivial to construct and maintain. This thesis develops an approach wherein the models are seeded based upon information extracted from the user's emails and from existing social networking sites. The main contribution of this thesis is in the specification of heuristics by which expertise and trustworthiness can be computed. It also provides a general schema and methodology by which additional sources of social information can be incorporated.
Commitment Alignment: Semantics, Patterns, and Decision Procedures for Distributed Computing
(2008-12-05) Chopra, Amit Khushwant; Dr. Rada Chirkova, Committee Member; Dr. S. Purushothaman Iyer, Committee Member; Dr. Mladen A. Vouk, Committee Member; Dr. Munindar P. Singh, Committee Chair
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.
An Event-Driven Approach to Agent-Based Business Process Enactment
(2007-05-29) Chakravarty, Payal; Dr. James C. Lester, Committee Member; Dr. Munindar P. Singh, Committee Chair; Dr. Xiaosong Ma, Committee Member
Agents enacting business processes in large open environments need to adaptively accommodate exceptions and opportunities. Work on multiagent approaches can flexibly model business processes. This thesis proposes an event-driven architecture that enriches such models with events to support agile enactment of processes. Specifically, we place this architecture in a business process framework based on protocols and policies, where agents' behaviors are specified via rules. The agents interact via messages, and agreements between them are modeled by commitments. These messages and commitments provide only a high-level view of the interactions and fail to capture fine-grained details of how the interactions were carried out and whether they were carried out smoothly or not. There might be hindrances due to internal and external influences during the process, resulting in anomalies in the business process enactment. Handling such exceptions or capturing opportunities will deviate the protocol from its routine path but restore the enactment process to a stable state. We attempt to achieve this by introducing fine-grained event monitoring at specific points of the process enactment that require special attention. Detected exceptions are handled by the agent's policies. Monitoring processes and thereby recovering from errors spontaneously, results in a more reliable and proactive distributed system. The contributions of this thesis include (1) an event-driven architecture, (2) a specification language that combines event logic with rules, (3) a methodology to incorporate events into a protocol for fine-grained monitoring, (4) an algorithm to help a designer derive high-level (complex) event patterns, (5) an algorithm to manage subscriptions to low-level events, and (6) policy-driven exception handling. This approach is applied on a well-known business scenario. A proof-of-concept prototype has been implemented to demonstrate the feasibility of the architecture. Some experiments have been carried out to demonstrate the different perspectives of commitments and different scenarios under which event monitoring proves to be useful.
Instant Messaging Interface and Transport for the MultiAgent Referral System.
(2003-04-14) Chatterjee, Subhayu; Dr. Robert St. Amant, Committee Member; Dr. Peng Ning, Committee Member; Dr. Munindar P. Singh, Committee Chair
Agent-based systems have been around for quite some time now. They have been extensively used in communication systems involving human interactions. The MultiAgent Referral System (MARS) helps automate the process of expertise location using referral chains. Previously, this system was implemented using email as the transport mechanism for the various referrals and queries generated by the agents. The asynchronous nature of email would prove restrictive in real-life scenario. This thesis develops an infrastructure using an Instant Messaging (IM) system that provides an user interface and transport mechanism for MARS. MARS has a distributed architecture and associates each user with an agent. This system is slightly different from a traditional IM system, which involves a client and a server, whereas in this case the messages from a user are routed through his agent to the server. Our specific approach exploits the open-source Jabber IM system, which enables us to integrate IM with MARS. In this manner, agent-to-agent communication is realized through IM and an IM-based user interface is provided to the users.
Modeling and Enacting Business Processes via Commitment Protocols Among Agents
(2005-12-08) Mallya, Ashok Ullal; Dr. Dennis R. Bahler, Committee Member; Dr. Munindar P. Singh, Committee Chair; Dr. Rada Y. Chirkova, Committee Member; Dr. James C. Lester, Committee Member
Multiagent systems involve a rich variety of interactions among agents—situated computations that are autonomous in their behavior and heterogenous in structure. These interactions can be realized unambiguously if they are governed by published protocols, since agents diverse in their structure and behavior can interact as long as they respect the protocols. However, traditional protocol specifications are unduly rigid for application in open settings involving autonomous entities. They represent protocols simply as an ordering of steps and stifle the participants' autonomy due to a lack of flexibility during enactment. Commitments among agents, which are akin to contractual obligations among businesses, are a powerful abstraction for modeling flexible protocols. Commitment-based design enables a more faithful model of the openness of the business world. However, modeling business interactions requires a rich variety of interaction protocols that can capture the needs of different applications. Whereas general (business) protocols might most flexibly characterize the interactions of their participants, protocols often must be refined based on the environment in which they are to be deployed, so as to yield improvements along various properties such as performance and risk outlay, when applied to real-world tasks such as in e-business. We introduce a formal semantics and an operational characterization for commitmentbased protocols wherein traditional software engineering notions such as refinement and aggregation are extended to apply to protocols. We also develop a principled approach for the design of such protocols in addition to methodologies for modeling and handling exceptions in them. We demonstrate, with appropriate examples, the benefits of this approach over traditional ones when applied to business process modeling and enactment. Our chief contributions are - A theoretical basis for describing protocol refinement using subsumption hierarchies and an algebra for composing protocols using existing ones. - A methodology for modeling and handling exceptions in commitment protocols that incorporates the preferences of the protocol designer and policies of the participants and enables specification of exceptions independent of the protocol specification. - Two methodologies for designing commitment protocols, one by enhancing an existing agent-oriented software engineering methodology, and another by deriving protocols from agent conversations. Our work draws from and contributes to agent communication, business process modeling and enactment, service-oriented computing, and software engineering.