Martin K. Purvis

Multiple determination of the optical constants of thin-film coating materials

The seven participating laboratories received films of two different thicknesses of Sc2O3 and Rh. All samples of each material were prepared in a single deposition run. Brief descriptions are given of the various methods used for determination of the optical constants of these coating materials. The measurement data are presented, and the results are compared. The mean of the variances of the Sc2O3 refractive-index determinations in the 0.40–0.75-nm spectral region was 0.03. The corresponding variances for the refractive index and absorption coefficient of Rh were 0.35 and 0.26, respectively.

Role model based mechanism for norm emergence in artificial agent societies

In this paper we propose a mechanism for norm emergence based on role models. The mechanism uses the concept of normative advice whereby the role models provide advice to the follower agents. Our mechanism is built using two layers of networks, the social link layer and the leadership layer. The social link network represents how agents are connected to each other. The leadership network represents the network that is formed based on the role played by each agent on the social link network. The two kinds of roles are leaders and followers. We present our findings on how norms emerge on the leadership network when the topology of the social link network changes. The three kinds of social link networks that we have experimented with are fully connected networks, random networks and scale-free networks.

Social norm emergence in virtual agent societies

The advent of virtual environments such as SecondLife call for a distributed approach for norm emergence and spreading. In open virtual environments, monitoring various interacting agents (avatars), using a centralized authority might be computationally expensive. The number of possible states and actions of an agent could be huge. An approach for sustaining order and smoother functioning of these environments can be facilitated through norms. Agents can generate norms based on interactions. In particular, those social norms that incur certain cost to an individual agent but benefit the whole society are more interesting than those benefit both the agent and the society. The problem is that the selfish agents might not be willing to share the norm adherence cost. In this work, we experiment with notion proposed by Axelrod that social norms are best at preventing small defections where the cost of enforcement is low. We also study how common knowledge can be used to faciliate the overall benefit of the society. We believe our work can be used to facilitate norm emergence in virtual online societies.

Ontologies for Interaction Protocols

In this paper we propose reducing the degree of human interpretation currently necessary to understand an interaction protocol by describing at an abstract level the required agent actions that must be ‘plugged into’ the protocol for it to be executed. In particular, this can be done by designing and publishing ontologies describing the input and output data that are processed during the protocol’s execution together with the actions and decisions that the agents must perform. An agent (or agent developer) that has previously defined mappings between the internal agent code and the actions and decisions in an ontology would then be able to interpret any interaction protocol that is defined with reference to that ontology. The discussion is based on the use of Coloured Petri Nets to represent interaction protocols and the Unified Modeling Language (UML) for ontology modelling. An alternative approach using Agent UML (AUML) is also outlined.

A deterministic energy-efficient clustering protocol for wireless sensor networks

Wireless sensor network (WSN) technologies have been employed in recent years for monitoring purposes in various domains from engineering industry to our home environment due to their ability to intelligently monitor remote locations. In this paper, we have developed a purely deterministic model that utilizes clustering to organize the WSN. We propose a deterministic energy-efficient clustering protocol that is dynamic, distributive, self-organizing and more energy efficient than the existing protocols. It utilizes a simplified approach which minimizes computational overhead-cost to self-organize the sensor network. Our simulation result shows a better performance with respect to energy consumption, which is reflected in the network lifetime in both homogeneous and heterogeneous settings when compared with the existing protocols. It is worthy of note that our approach approximates an ideal solution for balanced energy consumption in hierarchical wireless sensor networks.

Using artificial neural networks to model the suitability of coastline for breeding by New Zealand fur seals (Arctocephalus forsteri )

Abstract New Zealand fur seal ( Arctocephalus forsteri ) numbers and distribution were reduced by human exploitation but the species is now re-colonizing much of its former range. Pinnipeds occupy two different habitat media: the marine (feeding) and terrestrial (breeding) environments. Measures of geographic variation in both these environments can be modelled together to predict coastline suitability for colonization (i.e. potential availability of breeding sites). To avoid problems of non-linear modelling, we used an artificial neural network (ANN) to: (1) predict the suitability of coastline in South Island, New Zealand to support breeding A. forsteri colonies by creating a model using pup condition (measured from 20 breeding colonies during 1996–98), prey distribution and abundance, bathymetry, and the type of coastal substrate; (2) compare the predicted distribution of suitable coastline for colonization from the model to the current distribution of A. forsteri colonies ( n =198 colonies); and (3) using ANN inference rule extraction, determine which factors are the most influential in predicting coastline suitability. ANN model predictions overlapped current distributions of A. forsteri colonies in South Island. Inference rule extraction gave good predictions of colony performance (i.e. the ability to predict observed pup condition); however, they were not consistent among years in terms of the prey species constituting the rules or in the direction of the relationships. Arrow squid and octopus were important model terms in 1996 and 1997, but the direction of their coefficients in the inference rules were opposite between years. Hoki was an important term in 1997 and 1998, but it also varied in direction between years. Terms of secondary importance include the distance from sample colonies to 250 m-, 500 m- and 1000 m-isobaths. Variation in model predictions may result from climatic variation, the constant index of prey availability that was used and the potential for A. forsteri to switch main prey species among year. Resource availability appears to be a good predictor of the potential distribution of A. forsteri colonies, but future models should attempt to incorporate indices of temporal variation in resource availability as well as population density to better predict the colonization process and understand the ecological mechanisms operating within.

A MULTI-AGENT SYSTEM FOR THE INTEGRATION OF DISTRIBUTED ENVIRONMENTAL INFORMATION

Abstract This paper describes a multi-agent platform to be used for the integration of environmental information that may be distributed over a network. The system is designed to work as a collection of collaborating agents. Information sources are encapsulated as data source agents (DSAs) that accept messages in an agent communication language. Here we describe how queries can be entered into the system and information collected from multiple sources. A key component of the query module is the planner agent, which takes a query and transforms it first to a calculus, then to an algebraic expression in order to break it into subqueries which an executor agent can send to the DSAs. As part of this process, the query is translated from user-level ontologies to lower level ontologies relevant to the DSAs. Query results need not be returned within an ACL message, but may instead be represented by a Common Object Request Broker Architecture (CORBA) object reference which may be used to obtain the result set. The architecture and operation of these agent components is described and an example is presented of how environmental information can be queried.

Hardware/software codesign: a perspective

The authors propose that rather than maintain the traditional distinction between hardware and software engineering, a more fruitful approach to computer system design is to combine the hardware and software perspectives from the earliest stages of the design process and exploit the design flexibility and efficient allocation of function that such an approach offers. Since current hardware and software design methodologies have their differences, a unified codesign approach must be developed that will comprise both the hardware and software points of view. Increasingly, computer system design of the future will require this codesign approach. Custom chip design and ASIC design are discussed. Issues in codesign are considered.<<ETX>>

Norm emergence in agent societies formed by dynamically changing networks

In this paper we describe how our previously proposed role model agent mechanism for norm emergence can be applied to artificial agent societies with network topologies that are changing dynamically. Dynamically changing network topologies account for agents joining and leaving the network and the links that are created and removed between agents in a society. In order to construct a dynamically changing network we have adopted a model representing agents as particles colliding in a social space. We demonstrate that the role model agent mechanism for norm emergence works on top of dynamically created network topologies that represent social relationship structures.

Agent-based integration of Web Services with Workflow Management Systems

Rapid changes in the business environment call for more flexible and adaptive workflow systems. Researchers have proposed that Workflow Management Systems (WfMSs) comprising multiple agents can provide these capabilities. We have developed a multiagent based workflow system, JBees, which supports distributed process models and the adaptability of executing processes. Modern workflow systems should also have the flexibility to integrate available Web Services as they are updated. In this paper we discuss how our agent-based architecture can be used to bind and access Web Services in the context of executing a workflow process model.