Detecting exceptions in commitment protocols: Discovering hidden states

Open multiagent systems consist of autonomous agents that are built by different vendors. In principle, open multiagent systems cannot provide any guarantees about the behaviors of their agents. This means that when agents are working together, such as carrying out a business protocol, one agent’s misbehavior may potentially create an exception for another agent and obstruct its proper working. Faced with such an exception, an agent should be able to identify the problem by verifying the compliance of other agents. Previous work on verification of protocols unrealistically assume that participants have full knowledge of a protocol. However, when multiple agents enact a protocol, each agent has access to its part of the protocol and not more. This will require agents to check verification by querying others and more importantly by discovering the contracts between them. Here, we propose a commitment-based framework for detecting exceptions in which an agent augments its part of the protocol with its knowledge to construct states that are previously hidden to the agent by generating possible commitments between other agents. The agent then queries others to confirm those states. Our framework is built using C+ and Java, and is tested using a realistic delivery scenario

A Social Semantics for Agent Communication Languages

The ability to communicate is one of the salient properties of agents. Although a number of agent communication languages (ACLs) have been developed, obtaining a suitable formal semantics for ACLs remains one of the greatest challenges of multiagent systems theory. Previous semantics have largely been mentalistic in their orientation and are based solely on the beliefs and intentions of the participating agents. Such semantics are not suitable for most multiagent applications, which involve autonomous and heterogeneous agents, whose beliefs and intentions cannot be uniformly determined. Accordingly, we present a social semantics for ACLs that gives primacy to the interactions among the agents. Our semantics is based on social commitments and is developed in temporal logic. This semantics, because of its public orientation, is essential to providing a rigorous basis for multiagent protocols. This research was supported by the NCSU College of Engineering, the National Science Foundatio..

Correctness properties for multiagent systems

What distinguishes multiagent systems from other software systems is their emphasis on the interactions among autonomous, heterogeneous agents. This paper motivates and characterizes correctness properties for multiagent systems. These properties are centered on commitments, and capture correctness at a high level. In contrast to existing approaches, commitments underlie key correctness primitives understood in terms of meaning; for example, commitment alignment maps to interoperability; commitment discharge maps to compliance. This paper gives illustrative examples and characterizations of these and other properties. The properties cover the specification of the principal artifacts—protocols, roles, and agents—of an interaction-based approach to designing multiagent systems, and thus provide the formal underpinnings of the approach

Fractional Flow Theory Applicable to Non-Newtonian Behavior in EOR Processes

The method of characteristics, or fractional-flow theory, is extremely useful in understanding complex Enhanced Oil Recovery (EOR) processes and in calibrating simulators. One limitation has been its restriction to Newtonian rheology except in rectilinear flow. Its inability to deal with non-Newtonian rheology in polymer and foam EOR has been a serious limitation. We extend fractional flow methods for two-phase flow to non-Newtonian fluids in one-dimensional cylindrical flow, where rheology changes with distance from injection well. The fractional flow curve is then a function of position and we analyze the characteristic equations for two applications—polymer and foam floods. For polymer flooding, we present a semi-analytical solution for the changing fractional flow curve where characteristics and shocks collide. The semi-analytical solution is shown to give good agreement with the finite-difference simulation thus helping us understand the development and resolution of shocks. We discuss two separate cases of foam injection with or without preflush. We observe that the fractional flow solutions are more accurate than finite-difference simulations on a comparable grid and hence the method can be used to calibrate simulators. For SAG (alternating-slug) foam injection, characteristics and shocks collide, making the fractional-flow solution complex. Nonetheless, one can solve exactly for changing mobility near the well, to greater accuracy than with conventional simulation. The fractional-flow method extended to non-Newtonian flow can be useful both for its insights for scale-up of laboratory experiments and to calibrate computer simulators involving non-Newtonian EOR. It can also be an input to streamline simulations.GeotechnologyCivil Engineering and Geoscience