DSpace Community:
http://hdl.handle.net/2381/316
2015-05-25T15:30:14Z
2015-05-25T15:30:14Z
Performance and energy evaluation of RESTful web services in Raspberry Pi
Nunes, L. H.
Nakamura, L. H. V.
De F. Vieira, H..
De O. Libardi, R. M.
De Oliveira, E. M.
Estrella, J. C.
Reiff-Marganiec, Stephan
http://hdl.handle.net/2381/32267
2015-05-14T02:00:24Z
2015-05-13T10:06:24Z
Title: Performance and energy evaluation of RESTful web services in Raspberry Pi
Authors: Nunes, L. H.; Nakamura, L. H. V.; De F. Vieira, H..; De O. Libardi, R. M.; De Oliveira, E. M.; Estrella, J. C.; Reiff-Marganiec, Stephan
Abstract: Green computing has emerged as a hot topic leading to a need to understand energy consumption of computations. This need also extends to devices with limited resources as are common in the internet of things. RESTful services have shown their potential on such devices, but there are many choices of frameworks for their development and execution. Current research has analysed performance of the frameworks but no attention has been given to systematically studying their power consumption. In this paper we analyse the execution behaviour and power consumption of web services on devices with limited resources and make initial observations that should influence future development of web service frameworks. Specifically, we conduct experiments comparing web services in the Axis2 and CXF frameworks analysing the respective performance and power consumption. Bringing together the best features of small devices and SoC, it is possible to provide diverse, mobile and green applications - however careful selection of development environments can make significant differences in performance and energy consumption.
2015-05-13T10:06:24Z
Observing access control policies using scrabble games
Ahmad, S.
Abidin, S. Z. Z.
Omar, N.
Reiff-Marganiec, Stephan
http://hdl.handle.net/2381/32266
2015-05-14T02:00:26Z
2015-05-13T09:55:17Z
Title: Observing access control policies using scrabble games
Authors: Ahmad, S.; Abidin, S. Z. Z.; Omar, N.; Reiff-Marganiec, Stephan
Abstract: Access control is concerned with the policies that manage data sharing activities. Access control plays a crucial role in application areas such as education, health and business. However, most programming languages and programming environments do not naturally provide support for implementing access control policies requiring access control policies for systems to be coded as part of the development effort. Access control management policies are high-level features so having to involve a computer programmer during deployment stages for making changes to policies is costly. In this paper, we present an abstraction of access control management policies in the form of extended scrabble in its rules. The needs of access control policies program construct for supporting this game are examined. New relevant program constructs are then incorporated into JACIE (Java-based Authoring language for Collaborative Interactive Environments). The usefulness of these program construct are being demonstrated through the extended scrabble.
2015-05-13T09:55:17Z
Classifying Smart Objects using capabilities
Pérez Hernández, Marco E.
Reiff-Marganiec, Stephan
http://hdl.handle.net/2381/32265
2015-05-14T02:00:22Z
2015-05-13T09:46:00Z
Title: Classifying Smart Objects using capabilities
Authors: Pérez Hernández, Marco E.; Reiff-Marganiec, Stephan
Abstract: The Internet Of Things has emerged, providing an umbrella for the increasing number of heterogeneous Smart Objects that are becoming part of our daily activities. In this scenario, classification approaches are useful to understand differences and identify opportunities of generalization and common solutions, especially when different disciplines are coming together and bringing their individual terms and concepts. We propose a novel model for classifying Smart Objects using capabilities. This five-level model, inspired in the Capability Maturity Models, aims to be simple and inclusive, separating objects with basic capabilities from those with complex ones. In addition, examples of objects for each level are provided as validation of the proposal. The model is useful to identify requirements that Smart Objects have to cover externally as they cannot themselves support them and thus it allows for clear understanding of the external support system (or Middleware) into which the smart object is embedded.
2015-05-13T09:46:00Z
Design and implementation of fault tolerance techniques to improve QoS in SOA
Oliveira, E. M.
Estrella, J. C.
Kuehne, B. T.
Filho, D. M. L.
Adami, L. J.
Nunes, L. H.
Nakamura, L. H.
Libardi, R. M.
Souza, P. S. L.
Reiff-Marganiec, Stephan
http://hdl.handle.net/2381/32264
2015-05-14T02:00:22Z
2015-05-13T09:23:28Z
Title: Design and implementation of fault tolerance techniques to improve QoS in SOA
Authors: Oliveira, E. M.; Estrella, J. C.; Kuehne, B. T.; Filho, D. M. L.; Adami, L. J.; Nunes, L. H.; Nakamura, L. H.; Libardi, R. M.; Souza, P. S. L.; Reiff-Marganiec, Stephan
Abstract: Fault tolerance techniques can improve the trust of users in service oriented architectures as they can ensure data availability. This paper presents an implementation of a novel fault tolerance mechanism in a SOA architecture which simultaneously provides increased availability and better quality of service. In addition to this mechanism, a service selector using reputation ratings of the architecture components is discussed. The selection is based on information from past transactions of the components of the architecture, which allows to identify the best web services able to meet the requests of customers. The mechanisms are tested and a performance evaluation is presented to validate the results.
2015-05-13T09:23:28Z
A semantic approach for efficient and customized management of IaaS resources
Nakamura, L. H. V.
Estrella, J. C.
Santana, R. H. C.
Santana, M. J.
Reiff-Marganiec, Stephan
http://hdl.handle.net/2381/32263
2015-05-14T02:00:24Z
2015-05-13T09:15:14Z
Title: A semantic approach for efficient and customized management of IaaS resources
Authors: Nakamura, L. H. V.; Estrella, J. C.; Santana, R. H. C.; Santana, M. J.; Reiff-Marganiec, Stephan
Abstract: This paper presents a semantic approach to custom management of IaaS (Infrastructure as a Service) resources in a cloud computing environment requiring minimal human intervention from both the cloud provider and the user. The proposal differs from other approaches by using autonomic computing and semantic web techniques together to provide a self-configuring and self-optimizing environment that aims to satisfy SLAs (Service Level Agreements). The approach monitors the virtualized resources to guarantee a customized and optimized use based on financial criteria and energy consumption policies.
2015-05-13T09:15:14Z
Managing access control policy from end user perspective in collaborative environment
Ahmad, S.
Omar, N.
Abidin, S. Z. Z.
Reiff-Marganiec, Stephan
http://hdl.handle.net/2381/32252
2015-05-09T02:04:07Z
2015-05-08T14:55:00Z
Title: Managing access control policy from end user perspective in collaborative environment
Authors: Ahmad, S.; Omar, N.; Abidin, S. Z. Z.; Reiff-Marganiec, Stephan
Abstract: Currently, collaborative environments offer unlimited data sharing for users. Data owners are poorly involved in handling their data for such environment when it deals with data policy. Normally, data access control policy consists of a resource and authorization descriptions which are assigned by the administrator. It is the responsibility of the administrator to set and specify the policy for application services. The policy details are massive and complex for administrator to handle where most of the times there will be cases of unreview services. This paper proposes a framework that allows data owners to provision policies for storing and managing their shared data with third parties. By adapting RBAC model and adding owner's interest on permissions for data operations and objects, the proposed framework will facilitate data access control whereby owners have the freedom to set their own data access policy.
2015-05-08T14:55:00Z
HIAWSC: An Immune Algorithm Based Heuristic Web Service Composition Framework
Xu, J.
Reiff-Marganiec, Stephan
http://hdl.handle.net/2381/32251
2015-05-09T02:03:59Z
2015-05-08T14:39:51Z
Title: HIAWSC: An Immune Algorithm Based Heuristic Web Service Composition Framework
Authors: Xu, J.; Reiff-Marganiec, Stephan
Abstract: The introduction of of web services has led to web service composition being a focus of many researchers. Composing web services using workflows is seen as the most realistic method from an industrial viewpoint. Amongst other method, the use of natural computing methods has been proposed previously to automate web service composition. The need for a fast response when computing the most suitable sequence of services is addressed in this paper. In particular, we propose a novel heuristic immune algorithm with an efficient encoding and mutation method. The algorithm involves two steps: an immune selection operation, which is maintaining antibody population diversity and the clonal selection. The use of a vaccine during the evolution provides heuristic information that accelerates the convergence. Our experimental results illustrate that the proposed heuristic immune algorithm is very effective in improving the convergence speed. We also provide a schema analysis for this method.
2015-05-08T14:39:51Z
Performance Evaluation in a Cloud with the Provisioning of Different Resources Configurations
Batista, B. G.
Estrella, J. C.
Santana, M. J.
Santana, R. H. C.
Reiff-Marganiec, Stephan
http://hdl.handle.net/2381/32250
2015-05-09T02:03:54Z
2015-05-08T14:11:44Z
Title: Performance Evaluation in a Cloud with the Provisioning of Different Resources Configurations
Authors: Batista, B. G.; Estrella, J. C.; Santana, M. J.; Santana, R. H. C.; Reiff-Marganiec, Stephan
Abstract: Cloud computing is a computing style where resource providers can offer on-demand services in a transparent way and clients usually pay as they go. It introduces a new level of flexibility and scalability for IT users addressing challenges such as the rapid change in IT and the need to reduce cost and time of infrastructure management. However, to be able to offer QoS guarantees without limiting the number of accepted requests, providers must be able to dynamically adjust the available resources to serve requests. This dynamic resource management is not a trivial task, bringing its own challenges related to workload and performance modelling, and deployment and monitoring of applications on virtualised IT resources. An efficient mapping between resources and applications ensures workload balancing and good resource utilization and allows to meet the QoS levels required by clients. This paper presents a performance evaluation that considers different resource configurations in a cloud environment to define which dimension of resource scaling has real impact on client applications.
2015-05-08T14:11:44Z
Low-Latency Service Data Aggregation Using Policy Obligations
Reiff-Marganiec, Stephan
Tilly, M.
Janicke, H.
http://hdl.handle.net/2381/32249
2015-05-09T02:04:03Z
2015-05-08T13:59:21Z
Title: Low-Latency Service Data Aggregation Using Policy Obligations
Authors: Reiff-Marganiec, Stephan; Tilly, M.; Janicke, H.
Abstract: The Internet of Things, large scale sensor networks or even in social media, are now well established and their use is growing daily. Usage scenarios in these fields highlight the requirement to process, procure, and provide information with almost zero latency. This work is introducing new concepts for enabling fast communication by limiting information flow through filtering concepts combined with data processing techniques adopted from complex event processing. Specifically we introduce a novel mediation services architecture using filter policies to reduce latency. The filter policies define when and what data services need to provide to the mediator and thus save on bandwidth. The filter policies describe temporal conditions between two events removing the need to keep a complete history while still allowing temporal reasoning. Promising experimental results highlight the advantages to be gained from the approach.
2015-05-08T13:59:21Z
PEESOS: A Web Tool for Planning and Execution of Experiments in Service Oriented Systems
Nunes, L. H.
Vasconcelos Nakamura, L. H.
Tardiole Kuehne, B.
De Oliveira, E. M.
De O Libardi, R. M.
Junqueira Adami, L.
Estrella, J. C.
Reiff-Marganiec, Stephan
http://hdl.handle.net/2381/32241
2015-05-09T02:03:39Z
2015-05-08T10:56:39Z
Title: PEESOS: A Web Tool for Planning and Execution of Experiments in Service Oriented Systems
Authors: Nunes, L. H.; Vasconcelos Nakamura, L. H.; Tardiole Kuehne, B.; De Oliveira, E. M.; De O Libardi, R. M.; Junqueira Adami, L.; Estrella, J. C.; Reiff-Marganiec, Stephan
Abstract: Performing functionality testing in service-oriented architectures is not a trivial task. The difficulty is especially the large number of components that may be present in a SOA such as brokers, providers, service registries, clients, monitoring tools, data storage tools, etc. Thus, in order to facilitate the process of conducting functional testing and capacity planning in service-oriented systems, we present PEESOS. This first version is a functional prototype that offers facilities to assist researchers and industry to test their new applications, allowing collaborations that can be done between the participants to achieve an appropriate objective when developing a new application. The first results show that it is possible to make a planning environment easier to operate and to readily obtain results for performance evaluation of a target architecture. Since this is a first version of the prototype, it has interface and scalability limitations as well as needing improvements in performance of the logs repository and also in a core engine. We hope that such limitations can be corrected in the near future, including gathering information from the scientific community to make the prototype a useful and accessible tool. PEESOS is on-line and available at http://peesos.wsarch.lasdpc.icmc.usp.br.
Description: PEESOS is on-line and available at http://peesos.wsarch.lasdpc.icmc.usp.br.
2015-05-08T10:56:39Z
Providing Quality of Service on Services Selection Using Anycast Techniques
Adami, L. J.
Estrella, J. C.
De Oliveira, E. M.
Reiff- Marganiec, Stephan
http://hdl.handle.net/2381/32239
2015-05-09T02:03:40Z
2015-05-08T10:48:38Z
Title: Providing Quality of Service on Services Selection Using Anycast Techniques
Authors: Adami, L. J.; Estrella, J. C.; De Oliveira, E. M.; Reiff- Marganiec, Stephan
Abstract: Over the last years, the complexity and variety of services available on the Internet increased. This fact is leading to the search for efficient techniques of routing client requests to the best server available. A known technique is the application layer anycast (ALA). The main goal of this work is to elaborate efficient ways to provide ALA with quality of service in the context of cloud computing. To achieve this goal, we proposed a new algorithm (GALA, Global Application Layer Anycast). It inherits characteristics from another existing system (GAA, Global Application-layer Anycast), and uses geolocation as a differential. The results of the experiments show that GALA, compared to the inherited algorithm, maintains the client requests efficiencies and substantially lowers their latencies.
2015-05-08T10:48:38Z
A Utility-Aware Runtime Conflict Resolver for Composite Web services
Ning, X.
Xu, J.
Xu, N.
Reiff-Marganiec, Stephan
http://hdl.handle.net/2381/32237
2015-05-09T02:03:40Z
2015-05-08T10:40:16Z
Title: A Utility-Aware Runtime Conflict Resolver for Composite Web services
Authors: Ning, X.; Xu, J.; Xu, N.; Reiff-Marganiec, Stephan
Abstract: Web services are developed independently and
deployed in a distributed environment, new service can be
obtained by composing existing ones. The rapid introduction
of new services also results in undesirable interactions between
services. These conflicts are not mismatches of interfaces, but
are usually based on the data in the executing instance and
therefore runtime management of conflicts in Web services
should be considered. We study the problem from the perspective
of user’s revenue, and propose an online approach to
resolve conflicts is proposed.
2015-05-08T10:40:16Z
Study Case of Restful Frameworks in Raspberry Pi: A Perfomance and Energy Overview
Nunes, L. H.
Nakamura, L. H. V.
De F. Vieira, H.
De O. Libardi, R. M.
De Oliveira, E. M.
Adami, L. J.
Estrella, J. C.
Reiff-Marganiec, Stephan
http://hdl.handle.net/2381/32236
2015-05-09T02:03:38Z
2015-05-08T10:34:01Z
Title: Study Case of Restful Frameworks in Raspberry Pi: A Perfomance and Energy Overview
Authors: Nunes, L. H.; Nakamura, L. H. V.; De F. Vieira, H.; De O. Libardi, R. M.; De Oliveira, E. M.; Adami, L. J.; Estrella, J. C.; Reiff-Marganiec, Stephan
Abstract: This paper analyzes the execution behavior of web
services on devices with limited resources. The experiments
compare web services in the Axis2 and CXF frameworks
analyzing performance and power consumption. To determine
which framework is better suited for service provision, a testing
environment and a performance and energy evaluation between
them are presented. We show that the Raspberry Pi can be
useful in service-oriented applications for different types of
tasks. Bringing together the best features of small devices
and SoC, it is possible to provide diverse, mobile and green
applications.
2015-05-08T10:34:01Z
Fast Selection of Web Services with QoS using a Distributed Parallel Semantic Approach
Nakamura, L. H. V.
do Prado, P. F.
de O. Libardi, R. M.
Nunes, L. H.
Estrella, J. C.
Santana, R. H. C.
Santana, M. J.
Reiff-Marganiec, Stephan
http://hdl.handle.net/2381/32235
2015-05-09T02:00:23Z
2015-05-08T10:25:34Z
Title: Fast Selection of Web Services with QoS using a Distributed Parallel Semantic Approach
Authors: Nakamura, L. H. V.; do Prado, P. F.; de O. Libardi, R. M.; Nunes, L. H.; Estrella, J. C.; Santana, R. H. C.; Santana, M. J.; Reiff-Marganiec, Stephan
Abstract: This paper presents a solution to performance
issues in the quality of service aware selection of Web services
using techniques of parallelism and mechanisms of inference
provided by Semantic Web. The results point to a significant
improvement in the speed of searching Web services and thus
makes the use of semantic resources viable in distributed
systems to provide better quality of service to the clients.
2015-05-08T10:25:34Z
Encoding Data Structures
Raman, Rajeev
http://hdl.handle.net/2381/32217
2015-05-08T02:00:49Z
2015-05-07T13:20:56Z
Title: Encoding Data Structures
Authors: Raman, Rajeev
Abstract: In recent years, there has been an explosion of interest in
succinct data structures, which store the given data in compact or compressed
formats and answer queries on the data rapidly while it is still
in its compressed format. Our focus in this talk is to introduce encoding
data structures. Encoding data structures consider the data together
with the queries and aim to store only as much information about the
data as is needed to store the queries. Once this is done, the original data
can be deleted. In many cases, one can obtain space-efficient encoding
data structures even when the original data is incompressible.
Description: Abstract of invited talk.
2015-05-07T13:20:56Z
Compact Encodings and Indexes for the Nearest Larger Neighbor Problem
Jo, S.
Raman, Rajeev
Satti, S. R.
http://hdl.handle.net/2381/32215
2015-05-08T02:00:55Z
2015-05-07T13:05:29Z
Title: Compact Encodings and Indexes for the Nearest Larger Neighbor Problem
Authors: Jo, S.; Raman, Rajeev; Satti, S. R.
Abstract: Given a d-dimensional array, for any integer d > 0, the nearest
larger value (NLV) query returns the position of the element which
is closest, in L1 distance, to the query position, and is larger than the
element at the query position. We consider the problem of preprocessing
a given array, to construct a data structure that can answer NLV queries
efficiently. In the 2-D case, given an n × n array A, we give an asymptotically
optimal O(n
2
)-bit encoding that answers NLV queries in O(1)
time. When A is a binary array, we describe a simpler O(n
2
)-bit encoding
that also supports NLV queries in O(1) time. Using this, we obtain
an index of size O(n
2
/c) bits that supports NLV queries in O(c) time,
for any parameter c, where 1 ≤ c ≤ n, matching the lower bound. For
the 1-D case we consider the nearest larger right value (NLRV) problem
where the nearest larger value to the right is sought. For an array of
length n, we obtain an index that takes O((n/c) log c) bits, and supports
NLRV queries in O(c) time, for any any parameter c, where 1 ≤ c ≤ n,
improving the earlier results of Fischer et al. and Jayapaul et al.
2015-05-07T13:05:29Z
MSSF: A step towards user-friendly multi-cloud data dispersal
Libardi, R. M. de O.
Bedo, M. V. N.
Reiff-Marganiec, Stephan
Estrella, Julio C.
http://hdl.handle.net/2381/32118
2015-05-07T02:00:20Z
2015-05-06T12:06:35Z
Title: MSSF: A step towards user-friendly multi-cloud data dispersal
Authors: Libardi, R. M. de O.; Bedo, M. V. N.; Reiff-Marganiec, Stephan; Estrella, Julio C.
Abstract: With an increasing number of companies and individuals
adopting cloud computing for their data needs. Naturally,
there is a shift in financial and operational costs and and provided
services should meet users’ performance and cost expectations.
We focus on storage and propose MSSF, a Multi-cloud Storage
Selection Framework. MSSF contains a basic set of algorithms,
a set of security rules and a formal definition of user profiles
allowing to fit cloud storage services to user needs. Preliminary
experiments investigate the cost differences between two baseline
algorithms and user profile models. Considering the promising
initial results we provide several observations about the MSSF
decision making process that will help with future improvements.
2015-05-06T12:06:35Z
Survey of Aspect-Oriented Analysis and Design Approaches
Chitchyan, Ruzanna
Rashid, A.
Sawyer, P.
Garcia, A.
Alarcon, M. P.
Bakker, J.
Tekinerdogan, B.
Clarke, S.
Jackson, A.
http://hdl.handle.net/2381/32112
2015-05-18T01:45:07Z
2015-05-05T11:06:43Z
Title: Survey of Aspect-Oriented Analysis and Design Approaches
Authors: Chitchyan, Ruzanna; Rashid, A.; Sawyer, P.; Garcia, A.; Alarcon, M. P.; Bakker, J.; Tekinerdogan, B.; Clarke, S.; Jackson, A.
Abstract: A number of Aspect-Oriented (AO) Requirements, Architecture, and Design approaches have emerged recently. In this report we survey the most significant of these approaches, considering their origins, aims, and contributions. Alongside the AO approaches, we also analyse some of the contemporary non-AO work in order to bring out the differences between two sets of techniques, and to understand the potential contributions of aspect-oriented analysis and design. We also provide some initial insights into processes for AO requirements engineering, analysis and design which may serve as basis for integration of the work of the AOSD- EUROPE project partners. We also outline some issues relevant to such integration.
2015-05-05T11:06:43Z
Tractable Probabilistic μ-Calculus that Expresses Probabilistic Temporal Logics
Castro, P.
Kilmurray, C.
Piterman, Nir
http://hdl.handle.net/2381/32065
2015-04-25T02:04:03Z
2015-04-24T16:40:02Z
Title: Tractable Probabilistic μ-Calculus that Expresses Probabilistic Temporal Logics
Authors: Castro, P.; Kilmurray, C.; Piterman, Nir
Abstract: We revisit a recently introduced probabilistic μ-calculus and study an expressive fragment of it. By using the probabilistic quantification as an atomic operation of the calculus we establish a connection between the calculus and obligation games. The calculus we consider is strong enough to encode well-known logics such as pCTL and pCTL*. Its game semantics is very similar to the game semantics of the classical μ-calculus (using parity obligation games instead of parity games). This leads to an optimal complexity of NP intersection co-NP for its finite model checking procedure. Furthermore, we investigate a (relatively) well-behaved fragment of this calculus: an extension of pCTL with fixed points. An important feature of this extended version of pCTL is that its model checking is only exponential w.r.t. the alternation depth of fixed points, one of the main characteristics of Kozen's μ-calculus.
Description: 1998 ACM Subject Classification F.4.1 Mathematical Logic
2015-04-24T16:40:02Z
Assessing and generating test sets in terms of behavioural adequacy
Fraser, G.
Walkinshaw, Neil
http://hdl.handle.net/2381/31971
2015-04-11T02:03:09Z
2015-04-10T10:17:43Z
Title: Assessing and generating test sets in terms of behavioural adequacy
Authors: Fraser, G.; Walkinshaw, Neil
Editors: Offutt, J.
Abstract: Identifying a finite test set that adequately captures the essential behaviour of a program such that all faults are identified is a well-established problem. This is traditionally addressed with syntactic adequacy metrics (e.g. branch coverage), but these can be impractical and may be misleading even if they are satisfied. One intuitive notion of adequacy, which has been discussed in theoretical terms over the past three decades, is the idea of behavioural coverage: If it is possible to infer an accurate model of a system from its test executions, then the test set can be deemed to be adequate. Despite its intuitive basis, it has remained almost entirely in the theoretical domain because inferred models have been expected to be exact (generally an infeasible task) and have not allowed for any pragmatic interim measures of adequacy to guide test set generation. This paper presents a practical approach to incorporate behavioural coverage. Our bestest approach (1) enables the use of machine learning algorithms to augment standard syntactic testing approaches and (2) shows how search-based testing techniques can be applied to generate test sets with respect to this criterion. An empirical study on a selection of Java units demonstrates that test sets with higher behavioural coverage significantly outperform current baseline test criteria in terms of detected faults.
2015-04-10T10:17:43Z
Fairness for Infinite-State Systems
Cook, B.
Khlaaf, H.
Piterman, Nir
http://hdl.handle.net/2381/31957
2015-04-09T02:00:20Z
2015-04-08T09:51:07Z
Title: Fairness for Infinite-State Systems
Authors: Cook, B.; Khlaaf, H.; Piterman, Nir
Editors: Baier, C.; Tinelli , C.
Abstract: In this paper we introduce the first known tool for symbolically proving fair-CTL properties of (infinite-state) integer programs. Our solution is based on a reduction to existing techniques for fairness- free CTL model checking via the use of infinite non-deterministic branching to symbolically partition fair from unfair executions. We show the viability of our approach in practice using examples drawn from device drivers and algorithms utilizing shared resources.
Description: See also Research Note RN/14/11 UCL Department of Computer Science.
2015-04-08T09:51:07Z
From Communicating Machines to Graphical Choreographies
Lange, Julien
Tuosto, Emilio
Yoshida, Nobuko
http://hdl.handle.net/2381/31932
2015-03-28T03:00:22Z
2015-03-27T15:38:12Z
Title: From Communicating Machines to Graphical Choreographies
Authors: Lange, Julien; Tuosto, Emilio; Yoshida, Nobuko
Editors: Rajamani, S. K.; Walker, D.
Abstract: Graphical choreographies, or global graphs, are general multiparty session specifications featuring expressive constructs such as forking, merging, and joining for representing application-level protocols. Global graphs can be directly translated into modelling notations such as BPMN and UML. This paper presents an algorithm whereby a global graph can be constructed from asynchronous interactions represented by communicating finite-state machines (CFSMs). Our results include: a sound and complete characterisation of a subset of safe CFSMs from which global graphs can be constructed; an algorithm to translate CFSMs to global graphs; a time complexity analysis; and an implementation of our theory, as well as an experimental evaluation.
2015-03-27T15:38:12Z
Resolving non-determinism in choreographies
Bocchi, L.
Melgratti, H.
Tuosto, Emilio
http://hdl.handle.net/2381/31873
2015-03-17T02:02:13Z
2015-03-16T11:59:32Z
Title: Resolving non-determinism in choreographies
Authors: Bocchi, L.; Melgratti, H.; Tuosto, Emilio
Abstract: Resolving non-deterministic choices of choreographies is a crucial task. We introduce a novel notion of realisability for choreographies -called whole-spectrum implementation- that rules out deterministic implementations of roles that, no matter which context they are placed in, will never follow one of the branches of a non-deterministic choice. We show that, under some conditions, it is decidable whether an implementation is whole-spectrum. As a case study, we analyse the POP protocol under the lens of whole-spectrum implementation. © 2014 Springer-Verlag.
2015-03-16T11:59:32Z
Inferring Extended Finite State Machine Models from Software Executions
Walkinshaw, Neil
Taylor, R.
Derrick, J.
http://hdl.handle.net/2381/31765
2015-04-17T09:31:09Z
2015-03-04T16:59:57Z
Title: Inferring Extended Finite State Machine Models from Software Executions
Authors: Walkinshaw, Neil; Taylor, R.; Derrick, J.
Editors: Robbes, R.; Oliveto, R.; Di Penta, M.
Abstract: The ability to reverse-engineer models of software behaviour is valuable for a wide range of software maintenance, validation and verification tasks. Current reverse-engineering techniques focus either on control-specific behaviour (e.g., in the form of Finite State Machines), or data-specific behaviour (e.g., as pre / post-conditions or invariants). However, typical software behaviour is usually a product of the two; models must combine both aspects to fully represent the software's operation. Extended Finite State Machines (EFSMs) provide such a model. Although attempts have been made to infer EFSMs, these have been problematic. The models inferred by these techniques can be non-deterministic, the inference algorithms can be inflexible, and only applicable to traces with specific characteristics. This paper presents a novel EFSM inference technique that addresses the problems of inflexibility and non-determinism. It also adapts an experimental technique from the field of Machine Learning to evaluate EFSM inference techniques, and applies it to three diverse software systems.
2015-03-04T16:59:57Z
Minimum Spanning Tree Verification under Uncertainty
Erlebach, Thomas R.
Hoffmann, Michael
http://hdl.handle.net/2381/31666
2015-02-14T02:01:26Z
2015-02-13T11:59:12Z
Title: Minimum Spanning Tree Verification under Uncertainty
Authors: Erlebach, Thomas R.; Hoffmann, Michael
Abstract: In the verification under uncertainty setting, an algorithm is given, for each input item, an uncertainty area that is guaranteed to contain the exact input value, as well as an assumed input value. An update of an input item reveals its exact value. If the exact value is equal to the assumed value, we say that the update verifies the assumed value. We consider verification under uncertainty for the minimum spanning tree (MST) problem for undirected weighted graphs, where each edge is associated with an uncertainty area and an assumed edge weight. The objective of an algorithm is to compute the smallest set of updates with the property that, if the updates of all edges in the set verify their assumed weights, the edge set of an MST can be computed. We give a polynomial-time optimal algorithm for the MST verification problem by relating the choices of updates to vertex covers in a bipartite auxiliary graph. Furthermore, we consider an alternative uncertainty setting where the vertices are embedded in the plane, the weight of an edge is the Euclidean distance between the endpoints of the edge, and the uncertainty is about the location of the vertices. An update of a vertex yields the exact location of that vertex. We prove that the MST verification problem in this vertex uncertainty setting is NP-hard. This shows a surprising difference in complexity between the edge and vertex uncertainty settings of the MST verification problem.
2015-02-13T11:59:12Z
Query-competitive algorithms for cheapest set problems under uncertainty
Erlebach, Thomas
Hoffmann, Michael
Kammer, F.
http://hdl.handle.net/2381/31664
2015-02-14T02:01:39Z
2015-02-13T10:03:39Z
Title: Query-competitive algorithms for cheapest set problems under uncertainty
Authors: Erlebach, Thomas; Hoffmann, Michael; Kammer, F.
Abstract: Considering the model of computing under uncertainty where element weights are uncertain but can be obtained at a cost by query operations, we study the problem of identifying a cheapest (minimum-weight) set among a given collection of feasible sets using a minimum number of queries of element weights. For the general case we present an algorithm that makes at most d·OPT+d queries, where d is the maximum cardinality of any given set and OPT is the optimal number of queries needed to identify a cheapest set. For the minimum multi-cut problem in trees with d terminal pairs, we give an algorithm that makes at most d·OPT+1 queries. For the problem of computing a minimum-weight base of a given matroid, we give an algorithm that makes at most 2·OPT queries, generalizing a known result for the minimum spanning tree problem. For each of our algorithms we give matching lower bounds.
2015-02-13T10:03:39Z
Computational complexity of traffic hijacking under BGP and S-BGP
Chiesa, M.
Di Battista, G.
Patrignani, M.
Erlebach, Thomas
http://hdl.handle.net/2381/31661
2015-02-13T02:01:28Z
2015-02-12T15:21:43Z
Title: Computational complexity of traffic hijacking under BGP and S-BGP
Authors: Chiesa, M.; Di Battista, G.; Patrignani, M.; Erlebach, Thomas
Abstract: Harmful Internet hijacking incidents put in evidence how fragile the Border Gateway Protocol (BGP) is, which is used to exchange routing information between Autonomous Systems (ASes). As proved by recent research contributions, even S-BGP, the secure variant of BGP that is being deployed, is not fully able to blunt traffic attraction attacks. Given a traffic flow between two ASes, we study how difficult it is for a malicious AS to devise a strategy for hijacking or intercepting that flow. We show that this problem marks a sharp difference between BGP and S-BGP. Namely, while it is solvable, under reasonable assumptions, in polynomial time for the type of attacks that are usually performed in BGP, it is NP-hard for S-BGP. Our study has several by-products. E.g., we solve a problem left open in the literature, stating when performing a hijacking in S-BGP is equivalent to performing an interception.
2015-02-12T15:21:43Z
Approximation algorithms for disjoint st-paths with minimum activation cost
Alqahtani, Hasna Mohsen
Erlebach, Thomas
http://hdl.handle.net/2381/31648
2015-02-12T02:01:29Z
2015-02-11T13:28:34Z
Title: Approximation algorithms for disjoint st-paths with minimum activation cost
Authors: Alqahtani, Hasna Mohsen; Erlebach, Thomas
Abstract: In network activation problems we are given a directed or undirected graph G = (V,E) with a family {f (x, x) : (u,v) ∈ E} of monotone non-decreasing activation functions from D to {0,1}, where D is a constant-size domain. The goal is to find activation values x for all v ∈ V of minimum total cost Σ x such that the activated set of edges satisfies some connectivity requirements. Network activation problems generalize several problems studied in the network literature such as power optimization problems. We devise an approximation algorithm for the fundamental problem of finding the Minimum Activation Cost Pair of Node-Disjoint st-Paths (MA2NDP). The algorithm achieves approximation ratio 1.5 for both directed and undirected graphs. We show that a ρ-approximation algorithm for MA2NDP with fixed activation values for s and t yields a ρ-approximation algorithm for the Minimum Activation Cost Pair of Edge-Disjoint st-Paths (MA2EDP) problem. We also study the MA2NDP and MA2EDP problems for the special case |D| = 2.
2015-02-11T13:28:34Z
Multi-Type Display Calculus for Propositional Dynamic Logic
Frittella, S.
Greco, G.
Kurz, Alexander
Palmigiano, A.
http://hdl.handle.net/2381/31644
2015-02-12T02:01:31Z
2015-02-11T11:12:31Z
Title: Multi-Type Display Calculus for Propositional Dynamic Logic
Authors: Frittella, S.; Greco, G.; Kurz, Alexander; Palmigiano, A.
Abstract: We introduce a multi-type display calculus for Propositional Dynamic
Logic (PDL). This calculus is complete w.r.t. PDL, and enjoys Belnap-style
cut-elimination and subformula property.
2015-02-11T11:12:31Z
A Multi-type Display Calculus for Dynamic Epistemic Logic
Frittella, S.
Greco, G.
Kurz, Alexander
Palmigiano, A.
Sikimić, V.
http://hdl.handle.net/2381/31643
2015-02-12T02:01:30Z
2015-02-11T11:06:46Z
Title: A Multi-type Display Calculus for Dynamic Epistemic Logic
Authors: Frittella, S.; Greco, G.; Kurz, Alexander; Palmigiano, A.; Sikimić, V.
Abstract: In the present paper, we introduce a multi-type display calculus for dynamic
epistemic logic, which we refer to as Dynamic Calculus. The displayapproach
is suitable to modularly chart the space of dynamic epistemic logics
on weaker-than-classical propositional base. The presence of types endows
the language of the Dynamic Calculus with additional expressivity, allows
for a smooth proof-theoretic treatment, and paves the way towards a general
methodology for the design of proof systems for the generality of dynamic
logics, and certainly beyond dynamic epistemic logic. We prove that
the Dynamic Calculus adequately captures Baltag-Moss-Solecki’s dynamic
epistemic logic, and enjoys Belnap-style cut elimination.
2015-02-11T11:06:46Z
Establishing the Source Code Disruption Caused by Automated Remodularisation Tools
Hall, M.
Khojaye, Muhammad
Walkinshaw, Neil
McMinn, P.
http://hdl.handle.net/2381/31618
2015-02-06T02:01:58Z
2015-02-05T14:45:08Z
Title: Establishing the Source Code Disruption Caused by Automated Remodularisation Tools
Authors: Hall, M.; Khojaye, Muhammad; Walkinshaw, Neil; McMinn, P.
Editors: Poshyvanik, D.; Zaidman, A.
Abstract: Current software remodularisation tools only operate on abstractions of a software system. In this paper, we investigate the actual impact of automated remodularisation on source code using a tool that automatically applies remodularisations as refactorings. This shows us that a typical remodularisation (as computed by the Bunch tool) will require changes to thousands of lines of code, spread throughout the system (typically no code files remain untouched). In a typical multi-developer project this presents a serious integration challenge, and could contribute to the low uptake of such tools in an industrial context. We relate these findings with our ongoing research into techniques that produce iterative commit friendly code changes to address this problem.
2015-02-05T14:45:08Z
A Proof-Theoretic Semantic Analysis of Dynamic Epistemic Logic
Frittella, S.
Greco, G.
Kurz, Alexander H.
Palmigiano, A.
Sikimić, V.
http://hdl.handle.net/2381/31596
2015-02-05T02:01:33Z
2015-02-04T16:21:31Z
Title: A Proof-Theoretic Semantic Analysis of Dynamic Epistemic Logic
Authors: Frittella, S.; Greco, G.; Kurz, Alexander H.; Palmigiano, A.; Sikimić, V.
Editors: Aucher, G.; Hjortland, O.; Roy, O.
Abstract: The present article provides an analysis of the existing proof systems for dynamic epistemic logic from the viewpoint of proof-theoretic semantics. Dynamic epistemic logic is one of the best-known members of a family of logical systems that have been successfully applied to diverse scientific disciplines, but the proof-theoretic treatment of which presents many difficulties. After an illustration of the proof-theoretic semantic principles most relevant to the treatment of logical connectives, we turn to illustrating the main features of display calculi, a proof-theoretic paradigm that has been successfully employed to give a proof-theoretic semantic account of modal and substructural logics. Then, we review some of the most significant proposals of proof systems for dynamic epistemic logics, and we critically reflect on them in the light of the previously introduced proof-theoretic semantic principles. The contributions of the present article include a generalization of Belnap's cut-elimination metatheorem for display calculi, and a revised version of the display-style calculus D.EAK [30]. We verify that the revised version satisfies the previously mentioned proof-theoretic semantic principles, and show that it enjoys cut-elimination as a consequence of the generalized metatheorem.
2015-02-04T16:21:31Z
Minimum activation cost node-disjoint paths in graphs with bounded treewidth
Alqahtani, Hasna Mohsen
Erlebach, Thomas
http://hdl.handle.net/2381/31524
2015-01-31T02:01:32Z
2015-01-30T12:01:13Z
Title: Minimum activation cost node-disjoint paths in graphs with bounded treewidth
Authors: Alqahtani, Hasna Mohsen; Erlebach, Thomas
Abstract: In activation network problems we are given a directed or undirected graph G = (V,E) with a family {f uv : (u,v) ∈ E} of monotone non-decreasing activation functions from D2 to {0,1}, where D is a constant-size subset of the non-negative real numbers, and the goal is to find activation values xv for all v ∈ V of minimum total cost ∑ v ∈ V x v such that the activated set of edges satisfies some connectivity requirements. We propose algorithms that optimally solve the minimum activation cost of k node-disjoint st-paths (st-MANDP) problem in O(tw ((5 + tw)|D|)2tw + 2|V|3) time and the minimum activation cost of node-disjoint paths (MANDP) problem for k disjoint terminal pairs (s 1,t 1),…,(s k ,t k ) in O(tw ((4 + 3tw)|D|)2tw + 2|V|) time for graphs with treewidth bounded by tw.
2015-01-30T12:01:13Z
Nominal Lambda Calculus
Nebel, Frank
http://hdl.handle.net/2381/31396
2015-01-09T02:01:53Z
2015-01-08T15:07:38Z
Title: Nominal Lambda Calculus
Authors: Nebel, Frank
Abstract: Since their introduction, nominal techniques have been widely applied in computer
science to reason about syntax of formal systems involving name-binding operators.
The work in this thesis is in the area of “nominal" type theory, or more precisely the
study of “nominal" simple types.
We take Nominal Equational Logic (NEL), which augments equational logic with
freshness judgements, as our starting point to introduce the Nominal Lambda Calculus
(NLC), a typed lambda calculus that provides a simple form of name-dependent
function types. This is a key feature of NLC, which allows us to encode freshness in
a novel way.
We establish meta-theoretic properties of NLC and introduce a sound model theoretic
semantics. Further, we introduce NLC[A], an extension of NLC that captures
name abstraction and concretion, and provide pure NLC[A] with a strongly
normalising and confluent βη-reduction system.
A property that has not yet been studied for “nominal" typed lambda calculi is
completeness of βη-conversion for a nominal analogue of full set-theoretic hierarchies.
Aiming towards such a result, we analyse known proof techniques and identify various
issues. As an interesting precursor, we introduce full nominal hierarchies and
demonstrate that completeness holds for βη-conversion of the ordinary typed lambda
calculus.
The notion of FM-categories was developed by Ranald Clouston to demonstrate
that FM-categories correspond precisely to NEL-theories. We augment FM-categories
with equivariant exponentials and show that they soundly model NLC-theories. We
then outline why NLC is not complete for such categories, and discuss in detail an
approach towards extending NLC which yields a promising framework from which we
aim to develop a future (sound and complete) categorical semantics and a categorical
type theory correspondence.
Moreover, in pursuit of a categorical conservative extension result, we study (enriched/
internal) Yoneda isomorphisms for “nominal" categories and some form of
“nominal" gluing.
2015-01-08T15:07:38Z
CMMI-CM compliance checking of formal BPMN models using Maude
El-Saber, Nissreen A. S.
http://hdl.handle.net/2381/31390
2015-01-09T02:02:03Z
2015-01-08T12:29:00Z
Title: CMMI-CM compliance checking of formal BPMN models using Maude
Authors: El-Saber, Nissreen A. S.
Abstract: From the perspective of business process improvement models, a business process
which is compliant with best practices and standards (e.g. CMMI) is necessary for defining
almost all types of contracts and government collaborations. In this thesis, we propose
a formal pre-appraisal approach for Capability Maturity Model Integration (CMMI)
compliance checking based on a Maude-based formalization of business processes in
Business Process Model and Notation (BPMN). The approach can be used to assess
the designed business process compliance with CMMI requirements as a step leading
to a full appraisal application. In particular, The BPMN model is mapped into Maude,
and the CMMI compliance requirements are mapped into Linear Temporal Logic (LTL)
then the Maude representation of the model is model checked against the LTL properties
using the Maude’s LTL model checker.
On the process model side, BPMN models may include structural issues that hinder
their design. In this thesis, we propose a formal characterization and semantics specification
of well-formed BPMN processes using the formalization of rewriting logic (Maude)
with a focus on data-based decision gateways and data objects semantics. Our formal
specification adheres to the BPMN standards and enables model checking using Maude’s
LTL model checker. The proposed semantics is formally proved to be sound based on the
classical workflow model soundness definition. On the compliance requirements side,
CMMI configuration management process is used as a source of compliance requirements
which then are mapped through compliance patterns into LTL properties. Model
checking results of Maude based implementation are explained based on a compliance
grading scheme. Examples of CMMI configuration management processes are used to
illustrate the approach.
2015-01-08T12:29:00Z
Management concerns in service-driven applications
Alghamdi, Ahmed Musfer
http://hdl.handle.net/2381/30107
2014-12-16T02:17:29Z
2014-12-15T10:36:12Z
Title: Management concerns in service-driven applications
Authors: Alghamdi, Ahmed Musfer
Abstract: With the abundance of functionally-similar Web-Services, the offered or agreed-on qualities are becoming decisive factors in attracting private as well as corporate customers to a given service, among all others. Nevertheless, the state-of-art in handling qualities, in this emerging service paradigm, remains largely bound to the aspects of technology and their standards (e.g. time-response, availability, throughputs). However, current approaches still ignore capital domain-based business qualities and management concerns (e.g. customer profiles, business deadlines). The main objective of this thesis is to leverage the handling of quality and management issues in service-driven business applications toward the intuitive business level supported by a precise and flexible conceptualisation. Thus, instead of addressing qualities using just rigid IT-SLA (service-level agreements) as followed by Web Services technology and standards, we propose to cope with more abstract and domain-dependent and adaptive qualities in an intuitive, yet conceptual, manner. The approach is centred on evolving business rules and policies for management, with a clean separation of functionalities as specific rules. At the conceptual level, we propose specialised architectural connectors called management laws that we also separate from coordination laws for functionality issues. We further propose a smooth and compliant mapping of the conceptualisation toward service technology, using existing rule-based standards.
2014-12-15T10:36:12Z
Flexibo : language and its application to static analysis
Zhou, Jianguo
http://hdl.handle.net/2381/30106
2014-12-16T02:17:28Z
2014-12-15T10:36:12Z
Title: Flexibo : language and its application to static analysis
Authors: Zhou, Jianguo
Abstract: This thesis introduces a new object-based language FlexibO to support prototype development paradigm and more importantly, program static analysis. FlexibO offers extreme flexibility and hence enables developers to write programs that contain rich information for further analysis and optimization. FlexibO interpreter's seamless integration with Java (including direct access to Java classes and methods and direct inheritance of Java classes) makes it a suitable tool for fast prototype software development. FlexibO's extreme flexibility allows developers to redefine the behavior of program evaluation by overriding its default evaluation method. This mechanism can be used to translate FlexibO to other efficient languages. In this thesis we design a translator in FlexibO to translate Bulk-Synchronous Parallel specifications (expressed in FlexibO) to executable C pro grams linked with BSPLib. Before translation, the tool first checks syntax and type, then statically analyzes potential communication conflicts, and finally generates C code. The translation process can accurately analyze primitive commands but require approximation (using abstract interpretation) for more advanced commands such as loops. The appropriateness of the translator and the associated static analysis can be formally analyzed using the technique of normal form.
2014-12-15T10:36:12Z
Automatic presentations of groups and semigroups
Oliver, Graham
http://hdl.handle.net/2381/30105
2014-12-16T02:17:27Z
2014-12-15T10:36:10Z
Title: Automatic presentations of groups and semigroups
Authors: Oliver, Graham
Abstract: Effectively deciding the satisfiability of logical sentences over structures is an area well-studied in the case of finite structures. There has been growing work towards considering this question for infinite structures. In particular the theory of automatic structures, considered here, investigates structures representable by finite automata. The closure properties of finite automata lead naturally to algorithms for deciding satisfiability for some logics. The use of finite automata to investigate infinite structures has been inspired by the interplay between the theory of finite automata and the theory of semigroups. This inspiration has come in particular from the theory of automatic groups and semigroups, which considers (semi)groups with regular sets of normal forms over their generators such that generator-composition is also regular. The work presented here is a contribution to the foundational problem for automatic structures: given a class of structures, classify those members that have an automatic presentation. The classes considered here are various interesting subclasses of the class of finitely generated semigroups, as well as the class of Cayley Graphs of groups. Although similar, the theories of automatic (semi)groups and automatic presentation differ in their construction. A classification for finitely generated groups allows a direct comparison of the theory of automatic presentations with the theory of automatic groups.
2014-12-15T10:36:10Z
Optimization problems in communication networks
Mihalak, Matus
http://hdl.handle.net/2381/30104
2014-12-16T02:17:26Z
2014-12-15T10:36:09Z
Title: Optimization problems in communication networks
Authors: Mihalak, Matus
Abstract: We study four problems arising in the area of communication networks. The minimum-weight dominating set problem in unit disk graphs asks, for a given set D of weighted unit disks, to find a minimum-weight subset D' âŠ† D such that the disks D' intersect all disks D. The problem is NP-hard and we present the first constant-factor approximation algorithm. Applying our techniques to other geometric graph problems, we can obtain better (or new) approximation algorithms. The network discovery problem asks for a minimum number of queries that discover all edges and non-edges of an unknown network (graph). A query at node v discovers a certain portion of the network. We study two different query models and show various results concerning the complexity, approximability and lower bounds on competitive ratios of online algorithms. The OVSF-code assignment problem deals with assigning communication codes (nodes) from a complete binary tree to users. Users ask for codes of a certain depth and the codes have to be assigned such that (i) no assigned code is an ancestor of another assigned code and (ii) the number of (previously) assigned codes that have to be reassigned (in order to satisfy (i)) is minimized. We present hardness results and several algorithms (optimal, approximation, online and fixed-parameter tractable). The joint base station scheduling problem asks for an assignment of users to base stations (points in the plane) and for an optimal colouring of the resulting conflict graph: user u with its assigned base station b is in conflict with user v, if a disk with center at 6, and u on its perimeter, contains v. We study the complexity, and present and analyse optimal, approximation and greedy algorithms for general and various special cases.
2014-12-15T10:36:09Z
Categories of containers
Abbott, Michael Gordon
http://hdl.handle.net/2381/30102
2014-12-16T02:17:23Z
2014-12-15T10:36:09Z
Title: Categories of containers
Authors: Abbott, Michael Gordon
Abstract: This thesis develops a new approach to the theory of datatypes based on separating data and storage resulting in a class of datatype called a container. The extension of a container is a functor which can be regarded as a generalised polynomial functor in type variables. A representation theorem allows every natural transformation between container functors to be represented as a unique pair of morphisms in a category.;Under suitable assumptions on the ambient category container functors are closed under composition, limits, coproducts and the construction of initial algebras and final coalgebras. These closure properties allow containers to provide a functorial semantics for an important class of polymorphic types including the strictly positive types.;Since polymorphic functions between functorial polymorphic types correspond to natural transformations, every polymorphic function can be represented as a container morphism; this simplifies reasoning about such functions and provides a framework for developing concepts of generic programming.;Intuitionistic well-founded trees or W-types are the initial algebras of container functors in one parameter; the construction of the initial algebra of a container in more than one parameter leads to the solution of a problem left incomplete by earlier work of Dybjer.;We also find that containers provide a suitable framework to define the derivative of a functor as a kind of linear exponential. We show that the use of containers is essential for this approach.;The theory is developed in the context of a fairly general category to allow for a wide choice of applications. We use the language of dependent type theory to develop the theory of containers in an arbitrary extensive locally cartesian closed category; much of the development in this thesis can also be generalised to display map categories. We develop the appropriate internal language and its interpretation in a category with families.
2014-12-15T10:36:09Z
Formal languages and the irreducible word problem in groups
Fonseca, Ana
http://hdl.handle.net/2381/30103
2014-12-16T02:17:23Z
2014-12-15T10:36:09Z
Title: Formal languages and the irreducible word problem in groups
Authors: Fonseca, Ana
Abstract: There exist structural classifications of groups with a regular, one-counter or context-free word problem. Following on from this, the main object of the work presented here has been the irreducible word problem of a group, a notion introduced by Haring-Smith, who denned it as the subset of the word problem consisting of the non-empty words which have no non-empty proper subword equal to the identity. He proved that the groups with a finite irreducible word problem with respect to some group generating set are exactly the plain groups.;We know that the class of groups with a context-free irreducible word problem is a proper subclass of the virtually free groups. We look at direct products of finitely generated free groups by finite groups and also at the plain groups and consider their irreducible word problems with respect to minimal group generating sets. We prove that, of all the direct products of the infinite cyclic group by a non-trivial finite group, only Z x Z2 and Z x Z 3 have context-free irreducible word problem (and only with respect to a few group generating sets). We also exhibit a plain group that has context-free irreducible word problem with respect to every minimal group generating set.;Looking at the direct products of finitely generated free groups by non-trivial finite groups, we have found that the only irreducible word problem that is one-counter is that of Z x Z2 with respect to the canonical group generating set.;As for irreducible word problems lying in classes of languages above context-free, on one hand, we prove that having a recursive irreducible word problem is equivalent to having a recursive word problem. On the other hand, we prove that, while there are groups such that the fact that their irreducible word problem is recursively enumerable implies that they are recursive, that is not always the case.
2014-12-15T10:36:09Z
Alternative approaches to optophonic mappings
Capp, Michael.
http://hdl.handle.net/2381/30101
2014-12-16T02:17:22Z
2014-12-15T10:36:08Z
Title: Alternative approaches to optophonic mappings
Authors: Capp, Michael.
Abstract: This thesis presents a number of modifications to a blind aid, known as the video optophone, which enables a blind user to more readily interpret that local environment for enhanced mobility and navigation. Versions of this form of blind aid are generally both difficult to use and interpret, and are therefore inadequate for safe mobility. The reason for this severe problem lies in the complexity and excessive bandwidth of the optophonic output after the conversion from scene-to-sound.;The work herein describes a number of modifications that can be applied to the current optophonic process to make more efficient use of the limited bandwidth provided by the auditory system when converting scene images to sound. Various image processing and stereo techniques have been employed to artificially emulate the human visual system through the use of depth maps that successfully fade out the quantity of relatively unimportant image features, whilst emphasising the more significant regions such as nearby obstacles.;A series of experiments was designed to test these various modifications to the optophonic mapping by studying important factors of mobility and subject response whilst going about everyday life. The devised system, labelled DeLIA for the Detection, Location, Identification, and Avoidance (or Action) of obstacles, provided a means for gathering statistical data on users' interpretation of the optophonic output. An analysis of this data demonstrated a significant improvement when using the stereo cartooning technique, developed as part of this work, over the more conventional plain image as an input to an optophonic mapping from scene-to-sound.;Lastly, conclusions were drawn from the results, which indicated that the use of a stereo depth map as an input to a video optophone would improve its usefulness as an aid to general mobility. For the purposes of detecting and determining text or similar detail, either a plain unmodified image or some form of edge (depth) image were found to produce the best results.
2014-12-15T10:36:08Z
Multimodal human-computer interaction for enhancing customers’ decision-making and experience on B2C e-commerce websites
Al Sokkar, Abdullah Ahmad Musa
http://hdl.handle.net/2381/29330
2014-12-10T02:01:46Z
2014-12-09T11:49:14Z
Title: Multimodal human-computer interaction for enhancing customers’ decision-making and experience on B2C e-commerce websites
Authors: Al Sokkar, Abdullah Ahmad Musa
Abstract: The main aim of this thesis was to identify, complement and refine the factors that contribute to users’ intention to purchase, satisfaction and attitude toward using a particular B2C online environment, as well as the causal relationships between these factors. A systematic literature review on Information System (IS), Market Research, and User Experience (UX), which has informed the design and development of a pilot study, has been conducted. Results have led to the conception of an online shopping decision-making (OSDM) model called ‘Episodic UX Model on Decision-Making’ (EUX-DM). It has been developed by integrating the established Technology Acceptance Model (TAM) as well as Information System Success Model (ISSM), and emerging UX models, and Expectation-Confirmation Theory (ECT). Results from analysing 305 responses to the web-based questionnaire aimed to evaluate EUX-DM verified its validity. In addition, after investigating the users’ preferences for the possible modifications related to the use of visual avatar in a particular B2C e-Commerce website for information presentation, another research focus has been placed on identifying the real conversational functions and their related communicational behaviour in designing male and female visual avatars’ facial expressions and body gestures. Following this, four different types of information presentations have been developed to be used in a contrived B2C online shopping environment, namely: (i) 2D static graphical and textual information, (ii) non-expressive avatars, (iii) avatars with facial expressions, (iv) and avatars with facial expressions and body gestures information presentations. Consequently, these information presentations were empirically investigated through two experimental studies. The outcomes of these studies indicated that the gender of the avatar and participants were found to be insignificant factors for any of the measured qualities, and the use of visual avatars with animated facial expressions and body gestures positively influenced customers’ usage attitude, intention to purchase and satisfaction.
2014-12-09T11:49:14Z
Lem : Reusable engineering of real-world semantics
Mulligan, Dominic P.
Gray, Kathryn E.
Sewell, Peter
Owens, Scott
Ridge, Tom
http://hdl.handle.net/2381/29328
2014-12-10T02:01:48Z
2014-12-09T10:33:34Z
Title: Lem : Reusable engineering of real-world semantics
Authors: Mulligan, Dominic P.; Gray, Kathryn E.; Sewell, Peter; Owens, Scott; Ridge, Tom
Abstract: Recent years have seen remarkable successes in rigorous engineering: using mathematically rigorous semantic models (not just idealised calculi) of real-world processors, programming languages, protocols, and security mechanisms, for testing, proof, analysis, and design. Building these models is challenging, requiring experimentation, dialogue with vendors or standards bodies, and validation; their scale adds engineering issues akin to those of programming to the task of writing clear and usable mathematics. But language and tool support for specification is lacking. Proof assistants can be used but bring their own difficulties, and a model produced in one, perhaps requiring many person-years effort and maintained over an extended period, cannot be used by those familiar with another. We introduce Lem, a language for engineering reusable large-scale semantic models. The Lem design takes inspiration both from functional programming languages and from proof assistants, and Lem definitions are translatable into OCaml for testing, Coq, HOL4, and Isabelle/HOL for proof, and LaTeX and HTML for presentation. This requires a delicate balance of expressiveness, careful library design, and implementation of transformations - akin to compilation, but subject to the constraint of producing usable and human-readable code for each target. Lem's effectiveness is demonstrated by its use in practice. © 2014 ACM.
2014-12-09T10:33:34Z
Simple, efficient, sound and complete combinator parsing for all context-free grammars, using an oracle
Ridge, Tom
http://hdl.handle.net/2381/29327
2014-12-10T02:01:48Z
2014-12-09T10:20:37Z
Title: Simple, efficient, sound and complete combinator parsing for all context-free grammars, using an oracle
Authors: Ridge, Tom
Abstract: Parsers for context-free grammars can be implemented directly and naturally in a functional style known as “combinator parsing”, using recursion following the structure of the grammar rules. Traditionally parser combinators have struggled to handle all features of context-free grammars, such as left recursion.
Previous work introduced novel parser combinators that could be used to parse all context-free grammars. A parser generator built using these combinators was proved both sound and complete in the HOL4 theorem prover. Unfortunately the performance was not as good as other parsing methods such as Earley parsing.
In this paper, we build on this previous work, and combine it in novel ways with existing parsing techniques such as Earley parsing. The result is a sound-and-complete combinator parsing library that can handle all context-free grammars, and has good performance.
Description: timestamp: Tue, 09 Sep 2014 10:57:11 +0200 biburl: http://dblp.uni-trier.de/rec/bib/conf/sle/Ridge14 bibsource: dblp computer science bibliography, http://dblp.org
2014-12-09T10:20:37Z
On the Synthesis of Choreographies
Lange, Julien
http://hdl.handle.net/2381/29310
2014-12-05T02:01:48Z
2014-12-04T12:10:48Z
Title: On the Synthesis of Choreographies
Authors: Lange, Julien
Abstract: The theories based on session types stand out as effective methodologies
to specify and verify properties of distributed systems. A key result in the area shows the
suitability of choreography languages and session types as a basis for a choreography-driven
methodology for distributed software development. The methodology it advocates
is as follows: a team of programmers designs a global view of the interactions to be
implemented (i.e., a choreography), then the choreography is projected onto each role.
Finally, each program implementing one or more roles in the choreography is validated
against its corresponding projection(s).
This is an ideal methodology but it may not always be possible to design one set of
choreographies that will drive the overall development of a distributed system. Indeed,
software needs maintenance, specifications may evolve (sometimes also during the development),
and issues may arise during the implementation phase. Therefore, there is a
need for an alternative approach whereby it is possible to infer a choreography from local
behavioural specifications (i.e., session types).
We tackle the problem of synthesising choreographies from local behavioural specifications
by introducing a type system which assigns – if possible – a choreography to
set of session types. We demonstrate the importance of obtaining a choreography from
local specifications through two applications. Firstly, we give three algorithms and a
methodology to help software designers refine a choreography into a global assertion,
i.e., a choreography decorated with logical formulae specifying senders’ obligations and
receivers’ requirements. Secondly, we introduce a formal model for distributed systems
where each participant advertises its requirements and obligations as behavioural contracts
(in the form of session types), and where multiparty sessions are started when a set
of contracts allows to synthesise a choreography.
2014-12-04T12:10:48Z
User Activity Recognition through Software Sensors
Reiff-Marganiec, Stephan
http://hdl.handle.net/2381/29228
2015-01-01T02:45:05Z
2014-10-30T10:28:23Z
Title: User Activity Recognition through Software Sensors
Authors: Reiff-Marganiec, Stephan
Abstract: Context-aware systems are an instance of the ubiquitous or pervasive computing vision. They sense the users’ physical and virtual surrounding to identify the best system support for that user and adapt the system behaviour accordingly. The overall architecture of a context aware system can be broken into a number of logical aspects: gathering context data, storing the data, deriving knowledge through reasoning and mining and retrieving that knowledge to finally adapting system behaviours. Context is anything characterizing the environment of the user – their location, the ambient temperature, the people they are with, their current activity and some even consider the user’s mood. Traditionally context information has been gathered through the use of hardware sensors, such as GPS sensors or smart badges for locations and there has been work to track user’s eye movements at their desk to see which application they are using. However, determining the activity of a user has shown to be elusive to being sensed with hardware sensors. As users use web services more frequently they are exchanging messages with the services through the SOAP protocol. SOAP messages contain data, which is valuable if gathered and interpreted right – especially as this data can be shedding information on the activity of a user that goes beyond “sitting at the computer and typing”. We propose a complimentary sensor technology through the use of software sensors. The software sensors are essentially based on monitoring SOAP messages and inserting data for further reasoning and querying into a semantic context model. In this paper we consider details of extracting the data from SOAP messages in a non-obstructive way and show a solution to map the data from a SOAP message to our OWL ontology model automatically. On the latter, we specifically explain the methodology to map from SOAP messages to an existing structure of knowledge.
Description: The file associated with this record is embargoed until 18 months after the date of publication. The final published version may be available through the links above.
2014-10-30T10:28:23Z
Succinct indices for range queries with applications to orthogonal range maxima
Farzan, Arash
Munro, J. Ian
Raman, Rajeev
http://hdl.handle.net/2381/29206
2014-10-29T02:01:32Z
2014-10-28T10:40:48Z
Title: Succinct indices for range queries with applications to orthogonal range maxima
Authors: Farzan, Arash; Munro, J. Ian; Raman, Rajeev
Abstract: We consider the problem of preprocessing N points in 2D, each endowed with a priority, to answer the following queries: given a axis-parallel rectangle, determine the point with the largest priority in the rectangle. Using the ideas of the effective entropy of range maxima queries and succinct indices for range maxima queries, we obtain a structure that uses O(N) words and answers the above query in O(logN loglogN) time. This a direct improvement of Chazelle's result from 1985 [10] for this problem - Chazelle required O(N/ε) words to answer queries in O((logN)[superscript 1+ε]) time for any constant ε > 0.
2014-10-28T10:40:48Z
Succinct representations of ordinal trees
Raman, Rajeev
Rao, S. Srinivasa
http://hdl.handle.net/2381/29205
2014-10-29T02:01:31Z
2014-10-28T10:33:36Z
Title: Succinct representations of ordinal trees
Authors: Raman, Rajeev; Rao, S. Srinivasa
Abstract: We survey succinct representations of ordinal, or rooted, ordered trees. Succinct representations use space that is close to the appropriate information-theoretic minimum, but support operations on the tree rapidly, usually in O(1) time.
2014-10-28T10:33:36Z
On probabilistic models for uncertain sequential pattern mining
Muzammal, Muhammad
Raman, Rajeev
http://hdl.handle.net/2381/29204
2014-10-30T09:16:46Z
2014-10-28T10:26:52Z
Title: On probabilistic models for uncertain sequential pattern mining
Authors: Muzammal, Muhammad; Raman, Rajeev
Editors: Cao, L.; Feng, Y.; Zhong, J.
Abstract: We study uncertainty models in sequential pattern mining. We consider situations where there is uncertainty either about a source or an event. We show that both these types of uncertainties could be modelled using probabilistic databases, and give possible-worlds semantics for both. We then describe ”interestingness” criteria based on two notions of frequentness (previously studied for frequent itemset mining) namely expected support [C. Aggarwal et al. KDD’09;Chui et al., PAKDD’07,’08] and probabilistic frequentness [Bernecker et al., KDD’09]. We study the interestingness criteria from a complexity-theoretic perspective, and show that in case of source-level uncertainty, evaluating probabilistic frequentness is #P-complete, and thus no polynomial time algorithms are likely to exist, but evaluate the interestingness predicate in polynomial time in the remaining cases.
2014-10-28T10:26:52Z