DSpace Community:
http://hdl.handle.net/2381/316
2015-06-18T10:55:15Z
2015-06-18T10:55:15Z
Reducing Idle Listening during Data Collection in Wireless Sensor Networks
Rasul, Aram
Erlebach, Thomas
http://hdl.handle.net/2381/32370
2015-06-13T02:00:43Z
2015-06-12T09:26:08Z
Title: Reducing Idle Listening during Data Collection in Wireless Sensor Networks
Authors: Rasul, Aram; Erlebach, Thomas
Abstract: Data collection is one of the predominant operations in wireless sensor networks. This paper focuses on the problem of efficient data collection in a setting where some nodes may not possess data each time data is collected. In that case, idle listening slots may occur, which lead to a waste of energy and an increase in latency. To alleviate these problems, successive-slot schedules were proposed by Zhao and Tang (Infocom 2011). In this paper, we introduce a so-called extra-bit technique to reduce idle listening further. Each packet includes an extra bit that informs the receiver whether further data packets will follow or not. The extra-bit technique leads to significantly reduced idle listening and improved latency in many cases. We prove that every successive-slot schedule is also an extra-bit schedule. We then consider the special case of linear networks and prove that the optimal length of a successive-slot schedule (or extra-bit schedule) is 4N - 6 time slots, where N ≥ 3 is the number of nodes excluding the sink. Then the proposed extra-bit technique is compared with the successive-slot technique with respect to the expected amount of idle listening, and it is shown that the extra-bit technique reduces idle listening substantially.
Description: timestamp: Thu, 05 Mar 2015 11:05:43 +0100 biburl: http://dblp.uni-trier.de/rec/bib/conf/msn/RasulE14 bibsource: dblp computer science bibliography, http://dblp.org
2015-06-12T09:26:08Z
Mobile learning in a human geography field course
Jarvis, Claire
Tate, Nicholas
Dickie, Jennifer
Brown, Gavin
http://hdl.handle.net/2381/32345
2015-06-04T02:00:18Z
2015-06-03T09:03:12Z
Title: Mobile learning in a human geography field course
Authors: Jarvis, Claire; Tate, Nicholas; Dickie, Jennifer; Brown, Gavin
Editors: Mitchell, J.
Abstract: This paper reports on reusable mobile digital learning resources designed to assist human geography undergraduate students in exploring the geographies of life in Dublin. Developing active learning that goes beyond data collection to encourage observation and thinking in the field is important. Achieving this in the context of large class sizes presents several challenges. Combining in-situ learning with spatially-accurate historical and contemporary multimedia, we developed a set of location-aware digital mobile tools or ‘mediascapes’. We explore how scaffolding can be achieved in such a context, focusing on the development of students’ observational, enquiry and thinking skills in the field.
2015-06-03T09:03:12Z
The Price of Anarchy for Selfish Ring Routing is Two
Chen, Xujin
Doerr, Benjamin
Doerr, Carola
Hu, Xiaodong
Ma, Weidong
van Stee, Rob
http://hdl.handle.net/2381/32326
2015-06-01T14:54:05Z
2015-06-01T14:53:47Z
Title: The Price of Anarchy for Selfish Ring Routing is Two
Authors: Chen, Xujin; Doerr, Benjamin; Doerr, Carola; Hu, Xiaodong; Ma, Weidong; van Stee, Rob
Abstract: We analyze the network congestion game with atomic players, asymmetric strategies, and the maximum latency among all players as social cost. This important social cost function is much less understood than the average latency. We show that the price of anarchy is at most two, when the network is a ring and the link latencies are linear. Our bound is tight. This is the first sharp bound for the maximum latency objective.
Description: © ACM, 2014. This is the author's version of the work. It is posted here by permission of ACM for your personal use. Not for redistribution. The definitive version was published in ACM Transactions on Economics and Computation archive
Volume 2 Issue 2, June 2014 http://doi.acm.org/10.1145/2548545
2015-06-01T14:53:47Z
SIGACT news online algorithms column 24: 2014 so far
van Stee, Rob
http://hdl.handle.net/2381/32323
2015-06-01T10:56:07Z
2015-06-01T10:55:27Z
Title: SIGACT news online algorithms column 24: 2014 so far
Authors: van Stee, Rob
Abstract: In this column, I will discuss some recent papers in online algorithms. It is pleasing to see there
were a number of papers about online algorithms in the top conferences this year. If I have missed
your paper and you want to write about it or about any other topic in online algorithms, don't
hesitate to contact me!
2015-06-01T10:55:27Z
Better Algorithms for Online Bin Stretching
Böhm, Martin
Sgall, Jin
Stee, Rob van
Veselý, Pavel
http://hdl.handle.net/2381/32322
2015-06-01T10:44:37Z
2015-06-01T10:31:30Z
Title: Better Algorithms for Online Bin Stretching
Authors: Böhm, Martin; Sgall, Jin; Stee, Rob van; Veselý, Pavel
Abstract: Online Bin Stretching is a semi-online variant of bin packing in which the algorithm has to use the same number of bins as the optimal packing, but is allowed to slightly
overpack the bins. The goal is to minimize the amount of overpacking, i.e., the maximum
size packed into any bin.
We give an algorithm for Online Bin Stretching with a stretching factor of 1:5 for
any number of bins. We also show a specialized algorithm for three bins with a stretching
factor of 11=8 = 1:375.
Description: The final publication is available at Springer via http://dx.doi.org/10.1007/978-3-319-18263-6_3
2015-06-01T10:31:30Z
The optimal absolute ratio for online bin packing
Balogh, Janos
Békési, Jozsef
Dósa, Gyorgy
Sgall, Jiri
Stee, Rob van
http://hdl.handle.net/2381/32320
2015-06-01T09:53:41Z
2015-06-01T09:53:03Z
Title: The optimal absolute ratio for online bin packing
Authors: Balogh, Janos; Békési, Jozsef; Dósa, Gyorgy; Sgall, Jiri; Stee, Rob van
Abstract: We present an online bin packing algorithm with absolute competitive ratio 5/3, which is optimal.
2015-06-01T09:53:03Z
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
Black-Box Test Generation from Inferred Models
Papadopoulos, Petros
Walkinshaw, Neil
http://hdl.handle.net/2381/32206
2015-06-03T10:58:26Z
2015-05-07T10:44:39Z
Title: Black-Box Test Generation from Inferred Models
Authors: Papadopoulos, Petros; Walkinshaw, Neil
Abstract: Automatically generating test inputs for components
without source code (are ‘black-box’) and specification is challenging.
One particularly interesting solution to this problem is to
use Machine Learning algorithms to infer testable models from
program executions in an iterative cycle. Although the idea has
been around for over 30 years, there is little empirical information
to inform the choice of suitable learning algorithms, or to show
how good the resulting test sets are. This paper presents an
openly available framework to facilitate experimentation in this
area, and provides a proof-of-concept inference-driven testing
framework, along with evidence of the efficacy of its test sets on
three programs.
2015-05-07T10:44:39Z
Random access to grammar-compressed strings and trees
Bille, P.
Landau, G. M.
Raman, Rajeev
Sadakane, K.
Satti, S. R.
Weimann, O.
http://hdl.handle.net/2381/32182
2015-06-03T02:00:11Z
2015-05-07T10:26:27Z
Title: Random access to grammar-compressed strings and trees
Authors: Bille, P.; Landau, G. M.; Raman, Rajeev; Sadakane, K.; Satti, S. R.; Weimann, O.
Abstract: Grammar based compression, where one replaces a long string by a small context-free
grammar that generates the string, is a simple and powerful paradigm that captures (sometimes with
slight reduction in efficiency) many of the popular compression schemes, including the Lempel-Ziv
family, Run-Length Encoding, Byte-Pair Encoding, Sequitur, and Re-Pair. In this paper, we present
a novel grammar representation that allows efficient random access to any character or substring
without decompressing the string.
Let S be a string of length N compressed into a context-free grammar S of size n. We present
two representations of S achieving O(log N) random access time, and either O(n·αk(n)) construction
time and space on the pointer machine model, or O(n) construction time and space on the RAM.
Here, αk(n) is the inverse of the k th row of Ackermann’s function. Our representations also efficiently
support decompression of any substring in S: we can decompress any substring of length m in the
same complexity as a single random access query and additional O(m) time. Combining these
results with fast algorithms for uncompressed approximate string matching leads to several efficient
algorithms for approximate string matching on grammar compressed strings without decompression.
For instance, we can find all approximate occurrences of a pattern P with at most k errors in time
O(n(min{|P|k, k^4 + |P|} + log N) + occ), where occ is the number of occurrences of P in S. Finally,
we generalize our results to navigation and other operations on grammar-compressed ordered trees.
All of the above bounds significantly improve the currently best known results. To achieve these
bounds, we introduce several new techniques and data structures of independent interest, including
a predecessor data structure, two “biased” weighted ancestor data structures, and a compact
representation of heavy paths in grammars.
Description: AMS subject classifications. 68P05, 68P30
2015-05-07T10:26:27Z
CPT+: Decreasing the time/space complexity of the Compact Prediction Tree
Gueniche, T.
Fournier-Viger, P.
Raman, Rajeev
Tseng, V.
http://hdl.handle.net/2381/32181
2015-06-05T13:40:30Z
2015-05-07T10:25:53Z
Title: CPT+: Decreasing the time/space complexity of the Compact Prediction Tree
Authors: Gueniche, T.; Fournier-Viger, P.; Raman, Rajeev; Tseng, V.
Abstract: Predicting next items of sequences of symbols has many applications in a wide range of domains. Several sequence prediction models have been proposed such as DG, All-k-order markov and PPM. Recently, a model named Compact Prediction Tree (CPT) has been proposed. It relies on a tree structure and a more complex prediction algorithm to offer considerably more accurate predictions than many state-of-the-art prediction models. However, an important limitation of CPT is its high time and space complexity. In this article, we address this issue by proposing three novel strategies to reduce CPT’s size and prediction time, and increase its accuracy. Experimental results on seven real life datasets show that the resulting model (CPT+) is up to 98 times more compact and 4.5 times faster than CPT, and has the best overall accuracy when compared to six state-of-the-art models from the literature: All-K-order Markov, CPT, DG, Lz78, PPM and TDAG.
Description: Accepted as "REGULAR PAPER WITH LONG PRESENTATION" 27 of 405 submisisons accepted in this category.
2015-05-07T10:25:53Z
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
2015-06-01T01:45:08Z
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