Semantics of Agent Communication: An Introduction

Communication has been one of the salient issues in the research on concurrent and distributed systems. This holds no less for the research on multiagent systems. Over the last few years the study of agent communication, and in particular the semantics of agent communication, has attracted increased interest. The present paper provides an introduction to this area. Since agent communication builds upon concepts and techniques from concurrency theory , we start by giving a short historical overview that covers shared-variable concurrency, message-passing, rendezvous, concurrent constraint programming and agent communication. Standard approaches of agent communication identify three different layers: a content layer, message layer and communication layer. To this model we add an extra level, namely the layer of the multi-agent system. Subsequently, we discern three approaches in developing the semantics of programming languages: the axiomatic, operational and denotational approach. Additionally, we discuss semantic aspects of agent communication, including communication histories, compositionality, observable behaviour, failure sets and full abstractness. We illustrate these issues by means of the framework ACPL (Agent Communication Programming Language). Finally, we briefly consider the specification and verification of agent communication

Testing the discrimination and detection limits of WorldView-2 imagery on a challenging invasive plant target

Invasive plants pose significant threats to biodiversity and ecosystem function globally, leading to costly monitoring and management effort. While remote sensing promises cost-effective, robust and repeatable monitoring tools to support intervention, it has been largely restricted to airborne platforms that have higher spatial and spectral resolutions, but which lack the coverage and versatility of satellite-based platforms. This study tests the ability of the WorldView-2 (WV2) eight-band satellite sensor for detecting the invasive shrub mesquite (Prosopis spp.) in the north-west Pilbara region of Australia. Detectability was challenged by the target taxa being largely defoliated by a leaf-tying biological control agent (Gelechiidae: Evippe sp. #1) and the presence of other shrubs and trees. Variable importance in the projection (VIP) scores identified bands offering greatest capacity for discrimination were those covering the near-infrared, red, and red-edge wavelengths. Wavelengths between 400 nm and 630 nm (coastal blue, blue, green, yellow) were not useful for species level discrimination in this case. Classification accuracy was tested on three band sets (simulated standard multispectral, all bands, and bands with VIP scores ≥1).Overall accuracies were comparable amongst all band-sets (Kappa = 0.71–0.77). However, mesquite omission rates were unacceptably high (21.3%) when using all eight bands relative to the simulated standard multispectral band-set (9.5%) and the band-set informed by VIP scores (11.9%). An incremental cover evaluation on the latter identified most omissions to be for objects 16 m2 allows application for mapping mesquite shrubs and coalesced stands, the former not previously possible, even with 3 m resolution hyperspectral imagery. WV2 imagery offers excellent portability potential for detecting other species where spectral/spatial resolution or coverage has been an impediment. New generation satellite sensors are removing barriers previously preventing widespread adoption of remote sensing technologies in natural resource management