LRA Community:
http://hdl.handle.net/2381/316
Mon, 14 Apr 2014 03:40:05 GMT2014-04-14T03:40:05ZAn empirical evaluation of extendible arrays
http://hdl.handle.net/2381/28738
Title: An empirical evaluation of extendible arrays
Authors: Joannou, Stelios; Raman, Rajeev
Editors: Pardalos, PM; Rebennack, S
Abstract: We study the performance of several alternatives for implementing extendible arrays, which allow random access to elements stored
in them, whilst allowing the arrays to be grown and shrunk. The study
not only looks at the basic operations of grow/shrink and accessing data, but also the effects of memory fragmentation on performance.
Description: The final publication is
available at link.springer.comWed, 09 Apr 2014 10:40:44 GMThttp://hdl.handle.net/2381/287382014-04-09T10:40:44ZCell-cycle regulation of NOTCH signaling during C. elegans vulval development
http://hdl.handle.net/2381/28643
Title: Cell-cycle regulation of NOTCH signaling during C. elegans vulval development
Authors: Nusser-Stein, Stefanie; Beyer, Antje; Rimann, Ivo; Adamczyk, Magdalene; Piterman, Nir; Hajnal, Alex; Fisher, Jasmin
Abstract: C. elegans vulval development is one of the best‐characterized systems to study cell fate specification during organogenesis. The detailed knowledge of the signaling pathways determining vulval precursor cell (VPC) fates permitted us to create a computational model based on the antagonistic interactions between the epidermal growth factor receptor (EGFR)/RAS/MAPK and the NOTCH pathways that specify the primary and secondary fates, respectively. A key notion of our model is called bounded asynchrony, which predicts that a limited degree of asynchrony in the progression of the VPCs is necessary to break their equivalence. While searching for a molecular mechanism underlying bounded asynchrony, we discovered that the termination of NOTCH signaling is tightly linked to cell‐cycle progression. When single VPCs were arrested in the G1 phase, intracellular NOTCH failed to be degraded, resulting in a mixed primary/secondary cell fate. Moreover, the G1 cyclins CYD‐1 and CYE‐1 stabilize NOTCH, while the G2 cyclin CYB‐3 promotes NOTCH degradation. Our findings reveal a synchronization mechanism that coordinates NOTCH signaling with cell‐cycle progression and thus permits the formation of a stable cell fate pattern.Fri, 07 Mar 2014 13:50:41 GMThttp://hdl.handle.net/2381/286432014-03-07T13:50:41ZFaster temporal reasoning for infinite-state programs
http://hdl.handle.net/2381/28591
Title: Faster temporal reasoning for infinite-state programs
Authors: Piterman, Nir; Cook, Byron; Khlaaf, Heidy
Abstract: In many model checking tools that support temporal logic, performance is hindered by redundant reasoning performed in the presence of nested temporal operators. In particular, tools supporting the state-based temporal logic CTL often symbolically partition the system's state space using the sub-formulae of the input temporal formula. This can lead to repeated work when tools are applied to infinite-state programs, as often the characterization of the state-spaces for nearby program locations are similar and interrelated. In this paper, we describe a new symbolic procedure for CTL verification of infinite-state programs. Our procedure uses the structure of the program's control-flow graph in combination with the nesting of temporal operators in order to optimize reasoning performed during symbolic model checking. An experimental evaluation against competing tools demonstrates that our approach not only gains orders-of-magnitude performance speed improvement, but allows for scalability of temporal reasoning for larger programs.Thu, 20 Feb 2014 14:08:53 GMThttp://hdl.handle.net/2381/285912014-02-20T14:08:53ZStrongly complete logics for coalgebras
http://hdl.handle.net/2381/28587
Title: Strongly complete logics for coalgebras
Authors: Kurz, Alexander; Rosicky, Jiri
Abstract: Coalgebras for a functor model different types of transition systems in a uniform way. This paper focuses on a uniform account of finitary logics for set-based coalgebras. In particular, a general construction of a logic from an arbitrary set-functor is given and proven to be strongly complete under additional assumptions. We proceed in three parts. Part I argues that sifted colimit preserving functors are those functors that preserve universal algebraic structure. Our main theorem here states that a functor preserves sifted colimits if and only if it has a finitary presentation by operations and equations. Moreover, the presentation of the category of algebras for the functor is obtained compositionally from the presentations of the underlying category and of the functor. Part II investigates algebras for a functor over ind-completions and extends the theorem of J{'o}nsson and Tarski on canonical extensions of Boolean algebras with operators to this setting. Part III shows, based on Part I, how to associate a finitary logic to any finite-sets preserving functor T. Based on Part II we prove the logic to be strongly complete under a reasonable condition on T.Fri, 14 Feb 2014 10:52:40 GMThttp://hdl.handle.net/2381/285872014-02-14T10:52:40ZCompleteness for the coalgebraic cover modality
http://hdl.handle.net/2381/28586
Title: Completeness for the coalgebraic cover modality
Authors: Kupke, Clemens; Kurz, Alexander; Venema, Yde
Abstract: We study the finitary version of the coalgebraic logic introduced by L.Moss. The syntax of this logic, which is introduced uniformly with respect to a coalgebraic type functor, required to preserve weak pullbacks, extends that of classical propositional logic with a so-called coalgebraic cover modality depending on the type functor. Its semantics is defined in terms of a categorically defined relation lifting operation. As the main contributions of our paper we introduce a derivation system, and prove that it provides a sound and complete axiomatization for the collection of coalgebraically valid inequalities. Our soundness and completeness proof is algebraic, and we employ Pattinson's stratification method, showing that our derivation system can be stratified in countably many layers, corresponding to the modal depth of the formulas involved. In the proof of our main result we identify some new concepts and obtain some auxiliary results of independent interest. We survey properties of the notion of relation lifting, induced by an arbitrary but fixed set functor. We introduce a category of Boolean algebra presentations, and establish an adjunction between it and the category of Boolean algebras. Given the fact that our derivation system involves only formulas of depth one, it can be encoded as a endo-functor on Boolean algebras. We show that this functor is finitary and preserves embeddings, and we prove that the Lindenbaum-Tarski algebra of our logic can be identified with the initial algebra for this functor.Fri, 14 Feb 2014 10:40:06 GMThttp://hdl.handle.net/2381/285862014-02-14T10:40:06ZActivity awareness in context-aware systems using software sensors
http://hdl.handle.net/2381/28379
Title: Activity awareness in context-aware systems using software sensors
Authors: Pathan, Kamran Taj
Abstract: Context-aware systems being a component of ubiquitous or pervasive computing environment sense the users’ physical and virtual surrounding to adapt their behaviour accordingly. To achieve activity context tracking devices are common practice. Service Oriented Architecture is based on collections of services that communicate with each other. The communication between users and services involves data that can be used to sense the activity context of the user. SOAP is a simple protocol to let applications exchange their information over the web. Semantic Web provides standards to express the relationship between data to allow machines to process data more intelligently.
This work proposes an approach for supporting context-aware activity sensing using software sensors. The main challenges in the work are specifying context information in a machine processable form, developing a mechanism that can understand the data extracted from exchanges of services, utilising the data extracted from these services, and the architecture that supports sensing with software sensors. To address these issues, we have provided a bridge to combine the traditional web services with the semantic web technologies, a knowledge structure that supports the activity context information in the context-aware environments and mapping methods that extract the data out of exchanges occurring between user and services and map it into a context model. The Direct Match, the Synonym Match and the Hierarchical Match methods are developed to put the extracted data from services to the knowledge structure.
This research will open doors to further develop automated and dynamic context-aware systems that can exploit the software sensors to sense the activity of the user in the context-aware environments.Fri, 08 Nov 2013 15:49:07 GMThttp://hdl.handle.net/2381/283792013-11-08T15:49:07ZPure Type Systems with Corecursion on Streams: From Finite to Infinitary Normalisation
http://hdl.handle.net/2381/28332
Title: Pure Type Systems with Corecursion on Streams: From Finite to Infinitary Normalisation
Authors: Severi, Paula; de Vries, Fer-Jan
Abstract: In this paper, we use types for ensuring that programs involving streams are well-behaved.We extend pure type systems with a type constructor for streams, a modal operator next and a fixed point operator for expressing corecursion. This extension is called Pure Type Systems with Corecursion (CoPTS). The typed lambda calculus for reactive programs defined by Krishnaswami and Benton can be obtained as a CoPTS. CoPTSs allow us to study a wide range of typed lambda calculi extended with corecursion using only one framework. In particular, we study this extension for the calculus of constructions which is the underlying formal language of Coq. We use the machinery of infinitary rewriting and formalise the idea of well-behaved programs using the concept of infinitary normalisation. The set of finite and infinite terms is defined as a metric completion. We establish a precise connection between the modal operator (• A) and the metric at a syntactic level by relating a variable of type (• A) with the depth of all its occurrences in a term. This syntactic connection between the modal operator and the depth is the key to the proofs of infinitary weak and strong normalisation.Mon, 28 Oct 2013 15:24:43 GMThttp://hdl.handle.net/2381/283322013-10-28T15:24:43ZSuccinct Representations of Binary Trees for Range Minimum Queries
http://hdl.handle.net/2381/28331
Title: Succinct Representations of Binary Trees for Range Minimum Queries
Authors: Davoodi, Pooya; Raman, Rajeev; Satti, Satti Srinivasa
Abstract: We provide two succinct representations of binary trees that can be used to represent the Cartesian tree of an array A of size n. Both the representations take the optimal 2n + o(n) bits of space in the worst case and support range minimum queries (RMQs) in O(1) time. The first one is a modification of the representation of Farzan and Munro (SWAT 2008); a consequence of this result is that we can represent the Cartesian tree of a random permutation in 1.92n + o(n) bits in expectation. The second one uses a well-known transformation between binary trees and ordinal trees, and ordinal tree operations to effect operations on the Cartesian tree. This provides an alternative, and more natural, way to view the 2D-Min-Heap of Fischer and Huen (SICOMP 2011). Furthermore, we show that the pre-processing needed to output the data structure can be performed in linear time using o(n) bits of extra working space, improving the result of Fischer and Heun who use n + o(n) bits working space.Mon, 28 Oct 2013 13:05:12 GMThttp://hdl.handle.net/2381/283312013-10-28T13:05:12ZSuccinct representations of permutations and functions
http://hdl.handle.net/2381/28330
Title: Succinct representations of permutations and functions
Authors: Munro, J. Ian; Raman, Rajeev; Raman, Venkatesh; Rao, Satti Srinivasa
Abstract: We investigate the problem of succinctly representing an arbitrary permutation, π, on {0, . . . , n−1} so that π[superscript k](i) can be computed quickly for any i and any (positive or negative) integer power k. A representation taking (1 + ϵ)n lg n + O(1) bits suffices to compute arbitrary powers in constant time, for any positive constant ϵ ≤ 1. A representation taking the optimal ⌈lg n!⌉ + o(n) bits can be used to compute arbitrary powers in O(lg n/ lg lg n) time.
We then consider the more general problem of succinctly representing an arbitrary function, f : [n] → [n] so that f[superscript k](i) can be computed quickly for any i and any integer power k. We give a representation that takes (1 + ϵ)n lg n + O(1) bits, for any positive constant ϵ ≤ 1, and computes arbitrary positive powers in constant time. It can also be used to compute f[superscript k](i), for any negative integer k, in optimal O(1+ | f[superscript k](i) |) time. We place emphasis on the redundancy, or the space beyond the information-theoretic lower bound that the data structure uses in order to support operations efficiently. A number of lower bounds have recently been shown on the redundancy of data structures. These lower bounds confirm the space–time optimality of some of our solutions.
Furthermore, the redundancy of one of our structures "surpasses" a recent lower bound by Golynski [Golynski, SODA 2009], thus demonstrating the limitations of this lower bound.
Description: NOTICE: this is the author’s version of a work that was accepted for publication in Theoretical Computer Science. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Theoretical Computer Science, 2012, 438, pp. 47-88, DOI: 10.1016/j.tcs.2012.03.005.Mon, 28 Oct 2013 12:29:09 GMThttp://hdl.handle.net/2381/283302013-10-28T12:29:09ZDynamic Compressed Strings with Random Access
http://hdl.handle.net/2381/28247
Title: Dynamic Compressed Strings with Random Access
Authors: Grossi, Roberto; Raman, Rajeev; Rao, Satti Srinivasa; Venturini, Rossano
Abstract: We consider the problem of storing a string S in dynamic compressed form, while permitting operations directly on the compressed representation of S: access a substring of S; replace, insert or delete a symbol in S; count how many occurrences of a given symbol appear in any given prefix of S (called rank operation) and locate the position of the ith occurrence of a symbol inside S (called select operation). We discuss the time complexity of several combinations of these operations along with the entropy space bounds of the corresponding compressed indexes. In this way, we extend or improve the bounds of previous work by Ferragina and Venturini [TCS, 2007], Jansson et al. [ICALP, 2012], and Nekrich and Navarro [SODA, 2013].Fri, 04 Oct 2013 12:14:04 GMThttp://hdl.handle.net/2381/282472013-10-04T12:14:04ZMaintaining Transactional Integrity in Long Running Workflow Services: A Policy-Driven Framework
http://hdl.handle.net/2381/28168
Title: Maintaining Transactional Integrity in Long Running Workflow Services: A Policy-Driven Framework
Authors: Ali, Manar Sayed Salamah
Abstract: Business to Business integration is enhanced by Workflow structures, which allow for aggregating web services as interconnected business tasks to achieve a business outcome. Business processes naturally involve long running activities, and require transactional behavior across them addressed through general management, failure handling and compensation mechanisms. Loose coupling and the asynchronous nature of Web Services make an LRT subject to a wider range of communication failures. Two basic requirements of transaction management models are reliability and consistency despite failures. This research presents a framework to provide autonomous handling of long running transactions, based on dependencies which are derived from the workflow. The framework presents a solution for forward recovery from errors and compensations automatically applied to executing instances of workflows. The failure handling mechanism is based on the propagation of failures through a recursive hierarchical structure of transaction components (nodes and execution paths). The management system of transactions (COMPMOD) is implemented as a reactive system controller, where system components change their states based on rules in response to triggering of execution events. One practical feature of the model is the distinction of vital and non-vital components, allowing the process designer to express the cruciality of activities in the workflow with respect to the business logic. A novel feature of this research is that the approach permits the workflow designer to specify additional compensation dependencies which will be enforced. A notable feature is the extensibility of the model that is eased by the simple and declarative based formalism. In our approach, the main concern is the provision of flexible and reliable underlying control flow mechanisms supported by management policies. The main idea for incorporating policies is to manage the static structure of the workflow, as well as handling arbitrary failure and compensation events. Thus, we introduce new techniques and architectures to support enterprise integration solutions that support the dynamics of business needs.Thu, 12 Sep 2013 10:44:21 GMThttp://hdl.handle.net/2381/281682013-09-12T10:44:21ZComputing Minimum Spanning Trees with Uncertainty
http://hdl.handle.net/2381/28154
Title: Computing Minimum Spanning Trees with Uncertainty
Authors: Erlebach, Thomas; Hoffmann, Michael; Krizanc, Danny; Mihal’ák, Matúš; Raman, Rajeev
Editors: Albers, S.; Weil, P.
Abstract: We consider the minimum spanning tree problem in a setting where information about the edge weights of the given graph is uncertain. Initially, for each edge e of the graph only a set Aₑ, called an uncertainty area, that contains the actual edge weight wₑ is known. The algorithm can ‘update’ e to obtain the edge weight wₑ E Aₑ. The task is to output the edge set of a minimum spanning tree after a minimum number of updates.
An algorithm is k-update competitive if it makes at most k times as many updates as the optimum. We present a 2-update competitive algorithm if all areas Aₑ are open or trivial, which is the best possible among deterministic algorithms. The condition on the areas Aₑ is to exclude degenerate inputs for which no constant update competitive algorithm can exist.
Next, we consider a setting where the vertices of the graph correspond to points in Euclidean space and the weight of an edge is equal to the distance of its endpoints. The location of each point is initially given as an uncertainty area, and an update reveals the exact location of the point. We give a general relation between the edge uncertainty and the vertex uncertainty versions of a problem and use it to derive a 4-update competitive algorithm for the minimum spanning tree problem in the vertex uncertainty model. Again, we show that this is best possible among deterministic algorithms.Tue, 10 Sep 2013 13:05:03 GMThttp://hdl.handle.net/2381/281542013-09-10T13:05:03ZInferring Extended Finite State Machine Models from Software Executions
http://hdl.handle.net/2381/28128
Title: Inferring Extended Finite State Machine Models from Software Executions
Authors: Walkinshaw, Neil; Taylor, Ramsay; Derrick, John
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 two open-source software projects.Wed, 04 Sep 2013 09:00:20 GMThttp://hdl.handle.net/2381/281282013-09-04T09:00:20ZAttitudes towards User Experience (UX) Measurement
http://hdl.handle.net/2381/28125
Title: Attitudes towards User Experience (UX) Measurement
Authors: Law, Lai-Chong; van Schaik, Paul
Editors: Wiedenbeck, S
Abstract: User experience (UX), as an immature research area, is still haunted by the challenges of defining the scope of UX in general and operationalising experiential qualities in particular. To explore the basic question whether UX constructs are measurable, we conducted semi-structured interviews with eleven UX professionals where a set of questions in relation to UX measurement were explored. The interviewees expressed scepticism as well as ambivalence towards UX measures and shared anecdotes related to such measures in different contexts. Besides, the data suggested that design-oriented UX professionals tended to be sceptical about UX measurement. To examine whether such an attitude prevailed in the HCI community, we conducted a survey with essentially the same set of questions used in the interviews. Altogether 367 responses were received; 170 of them were valid and analysed. The survey provided empirical evidence on this issue as a baseline for progress in UX measurement. Overall, results indicated that attitude was favourable and there were nuanced views on details of UX measurement, implying good prospects for its acceptance, given further progress in research and education in UX measurement where UX modelling grounded in theories can play a crucial role. Mutual recognition of the value of objective measures and subjective accounts of user experience can enhance the maturity of this area.Tue, 03 Sep 2013 14:47:00 GMThttp://hdl.handle.net/2381/281252013-09-03T14:47:00ZAlgorithms for Wireless Communication and Sensor Networks
http://hdl.handle.net/2381/28100
Title: Algorithms for Wireless Communication and Sensor Networks
Authors: Grant, Thomas
Abstract: In this thesis we will address four problems concerned with algorithmic issues that arise from communication and sensor networks.
The problem of scheduling wireless transmissions under SINR constraints has received much attention for unicast (one to one) transmissions. We consider the scheduling problem for multicast requests of one sender to many receivers, and present a logarithmic approximation algorithm and an online lower bound for arbitrary power assignments.
We study the problem of maximising the lifetime of a sensor network for fault-tolerant target coverage in a setting with composite events, where a composite event is the simultaneous occurrence of one or more atomic events. We are the first to study this variation of the problem from a theoretical perspective, where each event must be covered twice and there are several event types, and we present a (6 + ɛ)-approximation algorithm for the problem.
The online strongly connected dominating set problem concerns the construction of a dominating set that is strongly connected at all times, and for every vertex not in the dominating set, there exists an edge to some vertex in the dominating set, and an edge from a vertex in the dominating set. We present a lower bound for deterministic online algorithms and present an algorithm that achieves competitive ratio matching the lower bound.
The monotone barrier resilience problem is to determine how many sensors must be removed from a sensor network, such that a monotone path can exist between two points that does not intersect any sensor. We present a polynomial time algorithm that can determine the monotone barrier resilience for sensor networks of convex pseudo-disks of equal width.Thu, 29 Aug 2013 10:44:20 GMThttp://hdl.handle.net/2381/281002013-08-29T10:44:20ZMining Sequential Patterns from Probabilistic Databases
http://hdl.handle.net/2381/28080
Title: Mining Sequential Patterns from Probabilistic Databases
Authors: Muzammal, Muhammad; Raman, Rajeev
Editors: Huang, J.Z.; Cao, L.; Srivastava, J.
Abstract: We consider sequential pattern mining in situations where there is uncertainty about which source an event is associated with. We model this in the probabilistic database framework and consider the problem of enumerating all sequences whose expected support is sufficiently large. Unlike frequent itemset mining in probabilistic databases [C. Aggarwal et al. KDD’09; Chui et al., PAKDD’07; Chui and Kao, PAKDD’08], we use dynamic programming (DP) to compute the probability that a source supports a sequence, and show that this suffices to compute the expected support of a sequential pattern. Next, we embed this DP algorithm into candidate generate-and-test approaches, and explore the pattern lattice both in a breadth-first (similar to GSP) and a depth-first (similar to SPAM) manner. We propose optimizations for efficiently computing the frequent 1-sequences, for re-using previously-computed results through incremental support computation, and for elmiminating candidate sequences without computing their support via probabilistic pruning. Preliminary experiments show that our optimizations are effective in improving the CPU cost.
Description: Full text of this item is not currently available on the LRA. The final published version may be available through the links above.Thu, 25 Jul 2013 10:38:00 GMThttp://hdl.handle.net/2381/280802013-07-25T10:38:00ZRange Extremum Queries
http://hdl.handle.net/2381/28079
Title: Range Extremum Queries
Authors: Raman, Rajeev
Abstract: There has been a renewal of interest in data structures for range extremum queries. In such problems, the input comprises N points, which are either elements of a d-dimensional matrix, that is, their coordinates are specified by the 1D submatrices they lie in (row and column indices for d = 2), or they are points in ℝ[superscript d] . Furthermore, associated with each point is a priority that is independent of the point’s coordinate. The objective is to pre-process the given points and priorities to answer the range maximum query (RMQ): given a d-dimensional rectangle, report the points with maximum priority. The objective is to minimze the space used by the data structure and the time taken to answer the above query. This talk surveys a number of recent developments in this area, focussing on the cases d = 1 and d = 2.Thu, 25 Jul 2013 09:04:54 GMThttp://hdl.handle.net/2381/280792013-07-25T09:04:54ZRandom Access to Grammar-Compressed Strings
http://hdl.handle.net/2381/28052
Title: Random Access to Grammar-Compressed Strings
Authors: Bille, Philip; Landau, Gad M.; Raman, Rajeev; Sadakane, Kunihiko; Satti, Srinivasa Rao; Weimann, Oren
Abstract: 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(logN) random access time, and either O(n · α[subscript k](n)) construction time and space on the pointer machine model, or 0(n) construction time and space on the RAM. Here, α[subscript k](n) is the inverse of the k[superscript 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[superscript 4] + |P|}+logN)+occ), where occ is the number of occurrences of P in S. Finally, we are able to generalize our results to navigation and other operations on grammar-compressed 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.Thu, 11 Jul 2013 12:05:53 GMThttp://hdl.handle.net/2381/280522013-07-11T12:05:53ZUsing Evidential Reasoning to Make Qualified Predictions of Software Quality
http://hdl.handle.net/2381/28050
Title: Using Evidential Reasoning to Make Qualified Predictions of Software Quality
Authors: Walkinshaw, Neil
Editors: Wagner, S
Abstract: Software quality is commonly characterised in a top-down manner. High-level notions such as quality are decomposed into hierarchies of sub-factors, ranging from abstract notions such as maintainability and reliability to lower-level notions such as test coverage or team-size. Assessments of abstract factors are derived from relevant sources of information about their respective lower-level sub-factors, by surveying sources such as metrics data and inspection reports. This can be difficult because (1) evidence might not be available, (2) interpretations of the data with respect to certain quality factors may be subject to doubt and intuition, and (3) there is no straightforward means of blending hierarchies of heterogeneous data into a single coherent and quantitative prediction of quality. This paper shows how Evidential Reasoning (ER) - a mathematical technique for reasoning about uncertainty and evidence - can address this problem. It enables the quality assessment to proceed in a bottom-up manner, by the provision of low-level assessments that make any uncertainty explicit, and automatically propagating these up to higher-level 'belief-functions' that accurately summarise the developer's opinion and make explicit any doubt or ignorance.Thu, 04 Jul 2013 15:35:16 GMThttp://hdl.handle.net/2381/280502013-07-04T15:35:16ZAnt Colony Optimization in Stationary and Dynamic Environments
http://hdl.handle.net/2381/27971
Title: Ant Colony Optimization in Stationary and Dynamic Environments
Authors: Mavrovouniotis, Michalis
Abstract: The ant colony optimization (ACO) metaheuristic is inspired by the foraging behaviour of real ant colonies. Similarly with other metaheuristics, ACO suffers from stagnation behaviour, where all ants construct the same solution from early stages.
In result, the solution quality may be degraded because the population may get trapped on local optima. In this thesis, we propose a novel approach, called direct communication (DC) scheme, that helps ACO algorithms to escape from a local optimum if they get trapped. The experimental results on two routing problems showed that the DC scheme is effective.
Usually, researchers are focused on problems in which they have static environment.
In the last decade, there is a growing interest to apply nature-inspired metaheuristics in optimization problems with dynamic environments. Usually, dynamic optimization problems (DOPs) are addressed using evolutionary algorithms. In this thesis, we apply several novel ACO algorithms in two routing DOPs. The proposed ACO algorithms are integrated with immigrants schemes in which immigrant ants are generated, either randomly or with the use of knowledge from previous environment(s), and replace other ants in the current population. The experimental results showed that each proposed algorithm performs better in different dynamic cases, and that they have better performance than other peer ACO algorithms in general.
The existing benchmark generators for DOPs are developed for binary-encoded combinatorial problems. Since routing problems are usually permutation-encoded combinatorial problems, the dynamic environments used in the experiments are generated using a novel benchmark generator that converts a static problem instance to a dynamic one. The specific dynamic benchmark generator changes the fitness landscape of the problem, which causes the optimum to change in every environmental change. Furthermore in this thesis, another benchmark generator is proposed which moves the population to another location in the fitness landscape, instead of modifying it. In this way, the optimum is known and one can see how close to the optimum an algorithm performs during the environmental changes.Fri, 14 Jun 2013 09:45:27 GMThttp://hdl.handle.net/2381/279712013-06-14T09:45:27ZCompleteness of Conversion between Reactive Programs for Ultrametric Models
http://hdl.handle.net/2381/27961
Title: Completeness of Conversion between Reactive Programs for Ultrametric Models
Authors: Severi, Paula; de Vries, Fer-Jan
Abstract: In 1970 Friedman proved completeness of beta eta conversion in the simply-typed lambda calculus for the set-theoretical model. Recently Krishnaswami and Benton have captured the essence of Hudak’s reactive programs in an extension of simply typed lambda calculus with causal streams and a temporal modality and provided this typed lambda calculus for reactive programs with a sound ultrametric semantics.
We show that beta eta conversion in the typed lambda calculus of reactive programs is complete for the ultrametric model.Tue, 11 Jun 2013 10:45:55 GMThttp://hdl.handle.net/2381/279612013-06-11T10:45:55ZBroadcasting, Coverage, Energy Efficiency and Network Capacity in Wireless Networks
http://hdl.handle.net/2381/27808
Title: Broadcasting, Coverage, Energy Efficiency and Network Capacity in Wireless Networks
Authors: Henna, Shagufta
Abstract: Broadcasting, coverage, duty cycling, and capacity improvement are some of the important areas of interest in Wireless Networks. We address different problems related with broadcasting, duty cycling, and capacity improvement by sensing different network conditions and dynamically adapting to them. We propose two cross layer broadcasting protocols called CASBA and CMAB which dynamically adapt to network conditions of congestion and mobility. We also propose a broadcasting protocol called DASBA which dynamically adapts to local node density. CASBA, CMAB, and DASBA improve the reachability while minimizing the broadcast cost. Duty cycling is an efficient mechanism to conserve energy in Wireless Sensor Networks (WSNs). Existing duty cycling techniques are unable to handle the contention under dynamic traffic loads. Our proposed protocol called SA-RI-MAC handles traffic contention much more efficiently than RI-MAC without sacrificing the energy efficiency. It improves the delivery ratio with a significant reduction in the latency and energy consumption. Due to limited battery life and fault tolerance issues posed by WSNs, efficient methods which ensure reliable coverage are highly desirable. One solution is to use disjoint set covers to cover the targets. We formulate a problem called MDC which addresses the maximum coverage by using disjoint set covers S1 and S2. We prove that MDC is NP-complete and propose a √n-approximation algorithm for the MDC problem to cover n targets. The use of multi-channel MAC protocols improves the capacity of wireless networks. Efficient multi-channel MAC protocols aim to utilize multiple channels effectively. Our proposed multi-channel MAC protocol called LCV-MMAC effectively utilizes the multiple channels by handling the control channel saturation. LCV-MMAC demonstrates significantly better throughput and fairness compared to DCA, MMAC, and AMCP in different network scenarios.Wed, 13 Mar 2013 11:14:56 GMThttp://hdl.handle.net/2381/278082013-03-13T11:14:56ZZooming out of Membrane Graph Transformation Systems
http://hdl.handle.net/2381/27791
Title: Zooming out of Membrane Graph Transformation Systems
Authors: Bapodra, Mayur
Abstract: Living cells offer a rich variety of complex interactions and interesting structures to those wishing to model processes in systems biology. Of particular interest is the hierarchical nature of cell configurations, the compartmentalized reactions that can occur within individual cells, and the interaction between different levels of this hierarchy. Graph transformation systems are an intuitive and readable modelling paradigm that lends itself to representing such systems since graphs can be utilised to represent this rich structural information, while graph rewriting rules can concisely describe cell reactions. We formulate a generic graph transformation model that captures many functional properties of membrane (or P) systems that take inspiration from such cell biological processes. The main focus is then on abstraction of systems defined as instances of this metamodel, which we refer to as membrane graph transformation systems. Often, such systems are analysed by stochastic simulation, as this allows us to examine their overall, emergent behaviour, incorporating the effect that randomness may have on the results. Stochastic simulation can be resource intensive, limiting the applicability of many modelling languages to real biological systems. To improve performance and the scalability of modelling, we formalize a methodology that hides detail in the lowest level of the hierarchy, but retains any important information as attributes. We then train the parameter of the abstract model using Bayesian networks so that the local, per-rule behaviour of the original, concrete model is preserved. Consequently, trends in global properties are preserved, such as the way in which they change with respect to the stochastic parameters of certain rules. The methodology is demonstrated and evaluated against two case studies: a hypothetical immunological response and a peer-to-peer voice over IP network.Tue, 12 Mar 2013 11:26:40 GMThttp://hdl.handle.net/2381/277912013-03-12T11:26:40ZThe SiXML Project: SiXDOM 1.2
http://hdl.handle.net/2381/27744
Title: The SiXML Project: SiXDOM 1.2
Authors: Delpratt, O’Neil; Joannou, Stelios; Rahman, Naila; Raman, Rajeev
Abstract: This White Paper introduces the SiXML project, developed by O’Neil Delpratt, Stelios Joannou, Naila Rahman and Rajeev Raman at the University of Leicester. SiXML uses the novel technology of succinct data structures to process XML documents in their entirety in main memory with a very low memory footprint. SiXML greatly improves the scalability of XML processing, both in terms of volume of data that can be handled and processing time. SiXML software can be downloaded in the accompanying zip file.
Description: This is an updated version of the SDOM 1.0 software available at http://hdl.handle.net/2381/3363.Fri, 08 Feb 2013 09:10:48 GMThttp://hdl.handle.net/2381/277442013-02-08T09:10:48ZMatching of Service Feature Diagrams based on Linear Logic
http://hdl.handle.net/2381/27741
Title: Matching of Service Feature Diagrams based on Linear Logic
Authors: Naeem, Muhammad
Abstract: Managing variability is essential for an efficient implementation of end-user services that can be customised to individual needs. Apart from variations in selection and orchestration, also third-party services may have to be customisable. Although feature diagrams provide a high-level visual notation for variability, their use for specifying variability of services raises the problem of matching a required feature diagram against a set of provided ones.
In particular, the established interpretation of feature diagrams in Propositional Logic is not expressive enough for matching in the context of service variability. The problem becomes more visible when a certain requirement is going to be satisfied by a combination of multiple offers with overlapping features, which is a consequence of idempotence in Propositional Logic.
To address this problem, we propose service feature diagrams with semantics in Linear Logic. Linear Logic only allows the use of idempotence on the propositions with modalities. The permissible selection of features of a service feature diagram is called an instance diagram. We provide rules to obtain instance diagrams from the service feature diagram. The semantics of instance diagrams are also supported by Linear Logic.
This thesis not only introduces service feature diagrams, but also formalises their matching as linear deduction. We propose two categories of rules to verify diagrammatically if a collection of service descriptions satisfy the requirements. First, graphical matching rules are used to match service feature diagrams of requestor and provider. Second, graphical merging rules are used to merge multiple feature diagrams contributing to satisfy the requestor’s demands. We prove the correctness of these rules using the inference system of Linear Logic. We also provide the analysis of graphical rules and show that the application of the graphical rules is independent of the context in service feature diagram, i.e., graphical rule can be applied anywhere in a service feature diagram.Thu, 07 Feb 2013 10:46:02 GMThttp://hdl.handle.net/2381/277412013-02-07T10:46:02ZOnline Algorithms for Temperature Aware Job Scheduling Problems
http://hdl.handle.net/2381/27686
Title: Online Algorithms for Temperature Aware Job Scheduling Problems
Authors: Birks, Martin David
Abstract: Temperature is an important consideration when designing microprocessors. When exposed to high temperatures component reliability can be reduced, while some components completely fail over certain temperatures. We consider the design and analysis of online algorithms; in particular algorithms that use knowledge of the amount of heat a job will generate. We consider algorithms with two main objectives. The first is maximising job throughput. We show upper and lower bounds for the case where jobs are unit length, both when jobs are weighted and unweighted. Many of these bounds are matching for all cooling factors in the single and multiple machine case.
We extend this to consider the single machine case where jobs have longer than unit length. When all jobs are equal length we show matching bounds for the case without preemption. We also show that both models of pre-emption enable at most a slight reduction in the competitive ratio of algorithms. We then consider when jobs have variable lengths. We analyse both the models of unweighted jobs and the jobs with weights proportional to their length. We show bounds that match within constant factors, in the non-preemptive and both preemptive models.
The second objective we consider is minimising flow time. We consider the objective of minimising the total flow time of a schedule. We show NP-hardness and inapproximability results for the offline case, as well as giving an approximation algorithm for the case where all release times are equal. For the online case we give some negative results for the case where maximum job heats are bounded. We also give some results for a resource augmentation model that include a 1-competitive algorithm when the extra power for the online algorithm is high enough. Finally we consider the objective of minimising the maximum flow time of any job in a schedule.Thu, 17 Jan 2013 11:55:28 GMThttp://hdl.handle.net/2381/276862013-01-17T11:55:28ZPartner-Based Scheduling and Routing for Grid Workflows
http://hdl.handle.net/2381/27683
Title: Partner-Based Scheduling and Routing for Grid Workflows
Authors: Ashraf, Jawad
Abstract: The Grid has enabled the scientific community to make faster progress. Scientific experiments and data analyses once spanning several years can now be completed in a matter of hours. With the advancement of technology, the execution of scientific experiments, often represented as workflows, has become more demanding. Thus, there is a vital need for improvements in the scheduling of scientific workflows. Efficient execution of scientific workflows can be achieved by the timely allocation of the resources. Advance reservation can ensure the future availability of heterogeneous resources and help a scheduler to produce better schedules.
We propose a novel resource mapping technique for jobs of a Grid workflow in an advance reservation environment. Using a dynamic critical path based job selection method, our proposed technique considers the conditional mapping of parent and child jobs to the same resource, trying to minimise the communication duration between jobs and thus optimising the workflow completion time. The proposed method is analysed in both static and dynamic environments, and the simulation results show encouraging performance especially for workflows where the communication costs are higher than the computation costs.
We also propose a hybrid of multiple scheduling heuristics for the aforementioned problem, which chooses the best among multiple schedules computed by different algorithms. Simulation results show a significant improvement over well known scheduling heuristics in terms of workflow completion time.
Considering the advance reservation environment, a better schedule for the earliest completion of a workflow can be achieved if better paths can be found for the transfer of data files between jobs executed on different resources. We propose a K-shortest path based routing algorithm for finding good paths in the advance reservation environment. The results show that our proposed algorithm performs very well in terms of the earliest arrival time of the data.
Finally, we also study a modified partner based scheduling heuristic for non-advance reservation environments. The results demonstrate that our proposed algorithm is a promising candidate for adoption in such Grid environments.Wed, 16 Jan 2013 14:15:54 GMThttp://hdl.handle.net/2381/276832013-01-16T14:15:54ZMining Sequential Patterns from Probabilistic Data
http://hdl.handle.net/2381/27638
Title: Mining Sequential Patterns from Probabilistic Data
Authors: Muzammal, Muhammad
Abstract: Sequential Pattern Mining (SPM) is an important data mining problem. Although it is assumed in classical SPM that the data to be mined is deterministic, it is now recognized that data obtained from a wide variety of data sources is inherently noisy or uncertain, such as data from sensors or data being collected from the web from different (potentially conflicting) data sources. Probabilistic databases is a popular framework for modelling uncertainty. Recently, several data mining and ranking problems have been studied in probabilistic databases. To the best of our knowledge, this is the first systematic study of mining sequential patterns from probabilistic databases.
In this work, we consider the kind of uncertainties that could arise in SPM. We propose four novel uncertainty models for SPM, namely tuple-level uncertainty, event-level uncertainty, source-level uncertainty and source-level uncertainty in deduplication, all of which fit into the probabilistic databases framework, and motivate them using potential real-life scenarios. We then define the interestingness predicate for two measures of interestingness, namely expected support and probabilistic frequentness. Next, we consider the computational complexity of evaluating the interestingness predicate, for various combinations of uncertainty models and interestingness measures, and show that different combinations have very different outcomes from a complexity theoretic viewpoint: whilst some cases are computationally tractable, we show other cases to be computationally intractable.
We give a dynamic programming algorithm to compute the source support probability and hence the expected support of a sequence in a source-level uncertain database. We then propose optimizations to speedup the support computation task. Next, we propose probabilistic SPM algorithms based on the candidate generation and pattern growth frameworks for the source-level uncertainty model and the expected support measure. We implement these algorithms and give an empirical evaluation of the probabilistic SPM algorithms and show the scalability of these algorithms under different parameter settings using both real and synthetic datasets. Finally, we demonstrate the effectiveness of the probabilistic SPM framework at extracting meaningful patterns in the presence of noise.Thu, 20 Dec 2012 11:37:59 GMThttp://hdl.handle.net/2381/276382012-12-20T11:37:59ZModel-Based Testing Using Visual Contracts
http://hdl.handle.net/2381/27571
Title: Model-Based Testing Using Visual Contracts
Authors: Khan, Tamim Ahmed
Abstract: Web services only expose interface level information, abstracting away implementation details. Testing is a time consuming and resource-intensive activity. Therefore, it is important to minimize the set of test cases executed without compromising quality. Since white-box testing techniques and traditional structural coverage criteria require access to code, we require a model-based approach for web service testing. Testing relies on oracles to provide expected outcomes for test cases and, if implemented manually, they depend on testers’ understanding of functional requirements to decide the correct response of the system on every given test case. As a result, they are costly in creation and maintenance and their quality depends on the correct interpretation of the requirements. Alternatively, if suitable specifications are available, oracles can be generated automatically at lower cost and with better quality. We propose to specify service operations as visual contracts with executable formal specifications as rules of a typed attributed graph transformation system. We associate operation signatures with these rules for providing test oracles.
We analyze dependencies and conflicts between visual contracts to develop a dependency graph. We propose model-based coverage criteria, considering this dependency graph, to assess the completeness of test suites. We also propose a mechanism to find out which of the potential dependencies and the conflicts were exercised by a given test case. While executing the tests, the model is simulated and coverage is recorded as well as measured against the criteria. The criteria are formalized and the dynamic detection of conflicts and dependencies is developed. This requires keeping track of occurrences and overlaps of pre- and post-conditions, their enabling and disabling, in successive model states, and interpreting these in terms of the static dependency graph.
Systems evolve over time and need retesting each time there is a change. In order to verify that the quality of the system is maintained, we use regression testing. Since regression test suites tend to be large, we isolate the affected part in the system only retesting affected parts by rerunning a selected subset of the total test suite. We analyze the test cases that were executed on both versions and propose a mechanism to transfer the coverage provided by these test cases. This information helps us to assess the completeness of the test suite on the new version without executing all of it.Fri, 02 Nov 2012 12:37:51 GMThttp://hdl.handle.net/2381/275712012-11-02T12:37:51ZPCTL model checking of Markov chains: Truth and falsity as winning strategies in games
http://hdl.handle.net/2381/26567
Title: PCTL model checking of Markov chains: Truth and falsity as winning strategies in games
Authors: Fecher, H; Huth, M; Piterman, N; Wagner, DWed, 24 Oct 2012 09:21:52 GMThttp://hdl.handle.net/2381/265672012-10-24T09:21:52ZA hierarchy of reverse bisimulations on stable configuration structures
http://hdl.handle.net/2381/26332
Title: A hierarchy of reverse bisimulations on stable configuration structures
Authors: Phillips, I; Ulidowski, IWed, 24 Oct 2012 09:21:34 GMThttp://hdl.handle.net/2381/263322012-10-24T09:21:34ZEnriched Logical Connections
http://hdl.handle.net/2381/21632
Title: Enriched Logical Connections
Authors: Kurz, A; Velebil, JWed, 24 Oct 2012 09:10:17 GMThttp://hdl.handle.net/2381/216322012-10-24T09:10:17ZSoft constraints of difference and equality
http://hdl.handle.net/2381/21619
Title: Soft constraints of difference and equality
Authors: Hebrard, E; Marx, D; O'Sullivan, B; Razgon, IWed, 24 Oct 2012 09:10:16 GMThttp://hdl.handle.net/2381/216192012-10-24T09:10:16ZFinitary functors: From set to Preord and Poset
http://hdl.handle.net/2381/21606
Title: Finitary functors: From set to Preord and Poset
Authors: Balan, A; Kurz, AWed, 24 Oct 2012 09:10:16 GMThttp://hdl.handle.net/2381/216062012-10-24T09:10:16ZRelation liftings on preorders and posets
http://hdl.handle.net/2381/21605
Title: Relation liftings on preorders and posets
Authors: Bílková, M; Kurz, A; Petrişan, D; Velebil, JWed, 24 Oct 2012 09:10:16 GMThttp://hdl.handle.net/2381/216052012-10-24T09:10:16ZVerifying Distributed Systems: the Operational Approach
http://hdl.handle.net/2381/20789
Title: Verifying Distributed Systems: the Operational Approach
Authors: Ridge, TWed, 24 Oct 2012 09:08:59 GMThttp://hdl.handle.net/2381/207892012-10-24T09:08:59ZEfficient algorithms for finding a longest common increasing subsequence
http://hdl.handle.net/2381/20787
Title: Efficient algorithms for finding a longest common increasing subsequence
Authors: Chan, W-T; Zhang, Y; Ye, D; Fung, SPY; Zhu, HWed, 24 Oct 2012 09:08:59 GMThttp://hdl.handle.net/2381/207872012-10-24T09:08:59ZThe semantics of x86-CC multiprocessor machine code
http://hdl.handle.net/2381/20788
Title: The semantics of x86-CC multiprocessor machine code
Authors: Sarkar, S; Sewell, P; Nardelli, FZ; Owens, S; Ridge, T; Braibant, T; Myreen, MO; Alglave, JWed, 24 Oct 2012 09:08:59 GMThttp://hdl.handle.net/2381/207882012-10-24T09:08:59ZRigorous protocol design in practice: An optical packet-switch MAC in HOL
http://hdl.handle.net/2381/20790
Title: Rigorous protocol design in practice: An optical packet-switch MAC in HOL
Authors: Biltcliffe, A; Ridge, T; Sewell, P; Dales, M; Jansen, SWed, 24 Oct 2012 09:08:59 GMThttp://hdl.handle.net/2381/207902012-10-24T09:08:59ZModelling user experience - An agenda for research and practice
http://hdl.handle.net/2381/20594
Title: Modelling user experience - An agenda for research and practice
Authors: Law, EL-C; Van Schaik PWed, 24 Oct 2012 09:08:51 GMThttp://hdl.handle.net/2381/205942012-10-24T09:08:51ZOn coalgebras over algebras
http://hdl.handle.net/2381/20595
Title: On coalgebras over algebras
Authors: Balan, A; Kurz, AWed, 24 Oct 2012 09:08:51 GMThttp://hdl.handle.net/2381/205952012-10-24T09:08:51ZMeasuring teachers' readiness for E-learning in higher education institutions associated with the subject of electricity in Turkey
http://hdl.handle.net/2381/20593
Title: Measuring teachers' readiness for E-learning in higher education institutions associated with the subject of electricity in Turkey
Authors: Akaslan, D; Law, EL-CWed, 24 Oct 2012 09:08:51 GMThttp://hdl.handle.net/2381/205932012-10-24T09:08:51ZForeword: Special issue on coalgebraic logic
http://hdl.handle.net/2381/20596
Title: Foreword: Special issue on coalgebraic logic
Authors: Doberkat, E-E; Kurz, AWed, 24 Oct 2012 09:08:51 GMThttp://hdl.handle.net/2381/205962012-10-24T09:08:51ZModal logics are coalgebraic
http://hdl.handle.net/2381/20598
Title: Modal logics are coalgebraic
Authors: Cîrstea, C; Kurz, A; Pattinson, D; Schröder, L; Venema, YWed, 24 Oct 2012 09:08:51 GMThttp://hdl.handle.net/2381/205982012-10-24T09:08:51ZEquational presentations of functors and monads
http://hdl.handle.net/2381/20597
Title: Equational presentations of functors and monads
Authors: Velebil, J; Kurz, AWed, 24 Oct 2012 09:08:51 GMThttp://hdl.handle.net/2381/205972012-10-24T09:08:51ZPresenting functors on many-sorted varieties and applications
http://hdl.handle.net/2381/20599
Title: Presenting functors on many-sorted varieties and applications
Authors: Kurz, A; Petrian, DWed, 24 Oct 2012 09:08:51 GMThttp://hdl.handle.net/2381/205992012-10-24T09:08:51ZCoalgebraic representations of distributive lattices with operators
http://hdl.handle.net/2381/20605
Title: Coalgebraic representations of distributive lattices with operators
Authors: Bonsangue, MM; Kurz, A; Rewitzky, IMWed, 24 Oct 2012 09:08:51 GMThttp://hdl.handle.net/2381/206052012-10-24T09:08:51ZAlgebraic semantics for coalgebraic logics
http://hdl.handle.net/2381/20607
Title: Algebraic semantics for coalgebraic logics
Authors: Kupke, C; Kurz, A; Pattinson, DWed, 24 Oct 2012 09:08:51 GMThttp://hdl.handle.net/2381/206072012-10-24T09:08:51ZFamilies of symmetries as efficient models of resource binding
http://hdl.handle.net/2381/20603
Title: Families of symmetries as efficient models of resource binding
Authors: Ciancia, V; Kurz, A; Montanari, UWed, 24 Oct 2012 09:08:51 GMThttp://hdl.handle.net/2381/206032012-10-24T09:08:51ZWeak factorizations, fractions and homotopies
http://hdl.handle.net/2381/20602
Title: Weak factorizations, fractions and homotopies
Authors: Kurz, A; Rosický, JWed, 24 Oct 2012 09:08:51 GMThttp://hdl.handle.net/2381/206022012-10-24T09:08:51Z