Spaceprint: a Mobility-based Fingerprinting Scheme for Public Spaces

In this paper, we address the problem of how automated situation-awareness can be achieved by learning real-world situations from ubiquitously generated mobility data. Without semantic input about the time and space where situations take place, this turns out to be a fundamental challenging problem. Uncertainties also introduce technical challenges when data is generated in irregular time intervals, being mixed with noise, and errors. Purely relying on temporal patterns observable in mobility data, in this paper, we propose Spaceprint, a fully automated algorithm for finding the repetitive pattern of similar situations in spaces. We evaluate this technique by showing how the latent variables describing the category, and the actual identity of a space can be discovered from the extracted situation patterns. Doing so, we use different real-world mobility datasets with data about the presence of mobile entities in a variety of spaces. We also evaluate the performance of this technique by showing its robustness against uncertainties

Specifying and Refining Internal Operations in Z

Abstract An important aspect in the specification of distributed systems is the role of the internal (or unobservable) operation. Such operations are not part of the interface to the environment (i.e. the user cannot invoke them), however, they are essential to our understanding and correct modelling of the system. In this paper we are interested in the use of the formal specification notation Z for the description of distributed systems. Various conventions have been employed to model internal operations when specifying such systems in Z. If internal operations are distinguished in the specification notation, then refinement needs to deal with internal operations in appropriate ways. Using an example of a telecommunications protocol we show that standard Z refinement is inappropriate for refining a system when internal operations are specified explicitly. We present a generalization of Z refinement, called weak refinement, which treats internal operations differently from observable operations when refining a system. We discuss the role of internal operations in a Z specification, and in particular whether an equivalent specification not containing internal operations can be found. The nature of divergence through livelock is also discussed. Keywords: Z; Refinement; Distributed Systems; Internal Operations; Process Algebras; Concurrency

Strategies for Consistency Checking

Viewpoint models of system development are becoming increasingly important. A major requirement for viewpoints modelling is to be able to check that the multiple viewpoint specifications are consistent with one another. The work presented in this report makes a contribution to this task. Our work is particularly influenced by the viewpoints model used in the ISO standardisation architecture for Open Distributed Processing. This report focuses on the issue of strategies for consistency checking. In particular, it considers how global consistency (between any arbitrary number of viewpoints) can be obtained from binary consistency (between two viewpoints). The report documents a number of different classes of consistency checking, from those that are very poorly behaved to those that are very well behaved. The report is intended as a companion to the work presented in [1] and it should be read in association with this document. In particular, the body of this report is a single chapter which should be viewed as additional to the chapters included in [1]. This report contains complete proofs of all relevant results, even though some of the results are obvious and some of the proofs are trivial. A much compressed version of the report is being submitted for publication. Thus, the main value of this report is as a reference document for readers who require a complete presentation of the technical. [1] E. Boiten, H. Bowman, J. Derrick and M. Steen ''Cross Viewpoint Consistency in Open Distributed Processing (Intra Language Consistency)'', Technical Report, Computing Laboratory, University of Kent at Canterbury, report No. 8-95, 1995. Phone: +44 1227 827913, Fax: 44 1227 762811 Email: H.Bowman,E.A.Boiten,J.Derrick,[email protected]

Unification and multiple views of data in Z

This paper discusses the unification of Z specifications, in particular specifications that maintain different representations of what is intended to be the same datatype. Essentially this amounts to integrating previously published techniques for combining multiple viewpoints and for combining multiple views. It is shown how the technique proposed in this paper indeed produces unifications, and that it generalises both previous techniques

Towards a Versatile Problem Diagnosis Infrastructure for LargeWireless Sensor Networks

In this position paper, we address the issue of durable maintenance of a wireless sensor network, which will be crucial if the vision of large, long-lived sensornets is to become reality. Durable maintenance requires tools for diagnosing and fixing occurring problems, which can range from internode connectivity losses, to time synchronization problems, to software bugs. While there are solutions for fixing problems, an appropriate diagnostic infrastructure is essentially still lacking. We argue that diagnosing a sensornet application requires the ability to dynamically and temporarily extend the application on a selected group of nodes with virtually any functionality. We motivate this claim based on deployment experiences to date and propose a highly nonintrusive solution to dynamically extending a running application on a resource-constrained sensor node

Simplified Distributed Programming with Micro Objects

Developing large-scale distributed applications can be a daunting task. object-based environments have attempted to alleviate problems by providing distributed objects that look like local objects. We advocate that this approach has actually only made matters worse, as the developer needs to be aware of many intricate internal details in order to adequately handle partial failures. The result is an increase of application complexity. We present an alternative in which distribution transparency is lessened in favor of clearer semantics. In particular, we argue that a developer should always be offered the unambiguous semantics of local objects, and that distribution comes from copying those objects to where they are needed. We claim that it is often sufficient to provide only small, immutable objects, along with facilities to group objects into clusters.Comment: In Proceedings FOCLASA 2010, arXiv:1007.499

Business Level Service-Oriented Enterprise Application Integration

In this paper we propose a new approach for service-oriented enterprise application integration (EAI). Unlike current EAI solutions, which mainly focus on technological aspects, our approach allows business domain experts to get more involved in the integration process. First, we provide a technique for modeling application services at a sufficiently high level of abstraction for business experts to work with. Next, these business experts can model the orchestration as well as the information mappings that are required to achieve their integration goals. Our mediation framework then takes over and realizes the integration solution by transforming these models to existing service orchestration technology