CODEWEAVE: exploring fine-grained mobility of code

This paper is concerned with an abstract exploration of code mobility constructs designed for use in settings where the level of granularity associated with the mobile units exhibits significant variability. Units of mobility that are both finer and coarser grained than the unit of execution are examined. To accomplish this, we take the extreme view that every line of code and every variable declaration are potentially mobile, i.e., it may be duplicated or moved from one program context to another on the same host or across the network. We also assume that complex code assemblies may move with equal ease. The result is CODEWEAVE, a model that shows how to develop new forms of code mobility, assign them precise meaning, and facilitate formal verification of programs employing them. The design of CODEWEAVE relies greatly on Mobile UNITY, a notation and proof logic for mobile computing. Mobile UNITY offers a computational milieu for examining a wide range of constructs and semantic alternatives in a clean abstract setting, i.e., unconstrained by compilation and performance considerations traditionally associated with programming language design. Ultimately, the notation offered by CODEWEAVE is given exact semantic definition by means of a direct mapping to the underlying Mobile UNITY model. The abstract and formal treatment of code mobility offered by CODEWEAVE establishes a technical foundation for examining competing proposals and for subsequent integration of some of the mobility constructs both at the language level and within middleware for mobility

Encrypted Shared Data Spaces

The deployment of Share Data Spaces in open, possibly hostile, environments arises the need of protecting the confidentiality of the data space content. Existing approaches focus on access control mechanisms that protect the data space from untrusted agents. The basic assumption is that the hosts (and their administrators) where the data space is deployed have to be trusted. Encryption schemes can be used to protect the data space content from malicious hosts. However, these schemes do not allow searching on encrypted data. In this paper we present a novel encryption scheme that allows tuple matching on completely encrypted tuples. Since the data space does not need to decrypt tuples to perform the search, tuple confidentiality can be guaranteed even when the data space is deployed on malicious hosts (or an adversary gains access to the host). Our scheme does not require authorised agents to share keys for inserting and retrieving tuples. Each authorised agent can encrypt, decrypt, and search encrypted tuples without having to know other agents’ keys. This is beneficial inasmuch as it simplifies the task of key management. An implementation of an encrypted data space based on this scheme is described and some preliminary performance results are given

Quantifying the errors in animal contacts recorded by proximity loggers

Automated contact detection by means of proximity loggers permits the measurement of encounters between individuals (animal-animal contacts) and the time spent by individuals in the proximity of a focal resource of interest (animal-fixed logger contacts). The ecological inference derived from contact detection is intrinsically associated with the distance at which the contact occurred. But no proximity loggers currently exist that record this distance and therefore all distance estimations are associated with error. Here we applied a probabilistic approach to model the relationship between contact detection and inter-logger distance, and quantify the associated error, on free-ranging animals in semi-controlled settings. The probability of recording a contact declined with the distance between loggers, and this decline was steeper for weaker radio transmission powers. Even when proximity loggers were adjacent, contact detection was not guaranteed, irrespective of the radio transmission power. Accordingly, the precision and sensitivity of the system varied as a function of inter-logger distance, radio transmission power, and experimental setting (e.g., depending on animal body mass and fine-scale movements). By accounting for these relationships, we were able to estimate the probability that a detected contact occurred at a certain distance, and the probability that contacts were missed (i.e., false negatives). These calibration exercises have the potential to improve the predictability of the study and enhance the applicability of proximity loggers to key wildlife management issues such as disease transmission rates or wildlife use of landscape features and resources

Message Quality for Ambient System Security

In ambient systems, a principal may be a physical object whose identity does not convey useful information for taking security decisions. Thus, establishing a trusted channel with a device depends more on the device being able to demonstrate what it does, rather than who it is. This paper proposes a security model that allows a principal to establish the intent of an adversary and to make the adversary prove its trustworthiness by furnishing proof of current and past behavior

Understanding processes of animal distribution and habitat choice: application of Wireless Sensor Networks to wildlife studies

Biologging, and especially those systems providing automated collection of animals’ positions, has certainly revolutionised the way to study animals in their environment, moving the observation point to animals themselves. However, the opportunity to integrate knowledge on animal movement with information gathered from the environment, has been largely overlooked so far, especially in terrestrial systems, where animal-borne data and environmental indexes are often collected in separate steps. Inferences on how habitat variables affect animal behaviour are therefore derived from post-hoc modelling, where animal activity, presence or distribution are modelled against a series of habitat variables. While this approach allowed to describe habitats of importance for species, it often failed to ascertain the processes at the basis of habitat choice and animal distribution in the environment. We propose the application of wireless sensor networks (WSNs) technology to terrestrial systems to design and effectively undertake hypothesis-based field experiment on habitat use. WSNs devices are equipped with a low-power microcontroller unit (MCU) enabling on-board computation, a wireless communication interface, storage memory, and a set of sensors. Thanks to this instrumentation and appropriate software control, the perspective to study habitat effects on individuals is totally reversed: when certain environmental conditions apply (e.g., temperature range, proximity to key resources, proximity among individuals), the device is activated to acquire an intense set of animal-borne and other data, thus providing a robust and quantitative basis for hypothesis validation. We present the results of simulation tests in challenging environments (e.g., tropical cloud forest, thick broad-leaved alpine forest), and discuss the potential of this system to study critical interaction between animal and resources (e.g., winter habitat use of ungulates in the Alps; proximity of zoonotic urban foxes to human settlements)

Lime: A Coordination Middleware Supporting Mobility of Hosts and Agents

LIME (Linda in a mobile environment) is a model and middleware supporting the development of applications that exhibit the physical mobility of hosts, logical mobility of agents, or both. LIME adopts a coordination perspective inspired by work on the Linda model. The context for computation, represented in Linda by a globally accessible persistent tuple space, is refined in LIME to transient sharing of the identically named tuple spaces carried by individual mobile units. Tuple spaces are also extended with a notion of location and programs are given the ability to react to specified states. The resulting model provides a minimalist set of abstractions that facilitates the rapid and dependable development of mobile applications. In this article we illustrate the model underlying LIME, provide a formal semantic characterization for the operations it makes available to the application developer, present its current design and implementation, and discuss lessons learned in developing applications that involve physical mobility

A fine-grained model for code mobility

In this paper we take the extreme view that every line of code is potentially mobile, i.e., may be duplicated and/or moved from one program context to another on the same host or across the network. Our motivation is to gain a better understanding of the range of constructs and issues facing the designer of a mobile code system, in a setting that is and unconstrained by compilation and performance considerations traditionally associated with programming language design. Incidental to our study is an evaluation of the expressive power of Mobile UNITY, a notation and proof logic for mobile computing