1,271 research outputs found
Interaction Grammars
Interaction Grammar (IG) is a grammatical formalism based on the notion of
polarity. Polarities express the resource sensitivity of natural languages by
modelling the distinction between saturated and unsaturated syntactic
structures. Syntactic composition is represented as a chemical reaction guided
by the saturation of polarities. It is expressed in a model-theoretic framework
where grammars are constraint systems using the notion of tree description and
parsing appears as a process of building tree description models satisfying
criteria of saturation and minimality
An integrated approach to high integrity software verification.
Computer software is developed through software engineering. At its most precise, software
engineering involves mathematical rigour as formal methods. High integrity software
is associated with safety critical and security critical applications, where failure
would bring significant costs. The development of high integrity software is subject to
stringent standards, prescribing best practises to increase quality. Typically, these standards
will strongly encourage or enforce the application of formal methods.
The application of formal methods can entail a significant amount of mathematical
reasoning. Thus, the development of automated techniques is an active area of research.
The trend is to deliver increased automation through two complementary approaches.
Firstly, lightweight formal methods are adopted, sacrificing expressive power, breadth of
coverage, or both in favour of tractability. Secondly, integrated solutions are sought,
exploiting the strengths of different technologies to increase automation.
The objective of this thesis is to support the production of high integrity software by
automating an aspect of formal methods. To develop tractable techniques we focus on
the niche activity of verifying exception freedom. To increase effectiveness, we integrate
the complementary technologies of proof planning and program analysis. Our approach
is investigated by enhancing the SPARK Approach, as developed by Altran Praxis Limited.
Our approach is implemented and evaluated as the SPADEase system. The key
contributions of the thesis are summarised below:
• Configurable and Sound - Present a configurable and justifiably sound approach
to software verification.
• Cooperative Integration - Demonstrate that more targeted and effective automation
can be achieved through the cooperative integration of distinct technologies.
• Proof Discovery - Present proof plans that support the verification of exception
freedom.
• Invariant Discovery - Present invariant discovery heuristics that support the verification
of exception freedom.
• Implementation as SPADEase - Implement our approach as SPADEase.
• Industrial Evaluation - Evaluate SPADEase against both textbook and industrial
subprograms
Exploiting Social Network Structure for Person-to-Person Sentiment Analysis
Person-to-person evaluations are prevalent in all kinds of discourse and
important for establishing reputations, building social bonds, and shaping
public opinion. Such evaluations can be analyzed separately using signed social
networks and textual sentiment analysis, but this misses the rich interactions
between language and social context. To capture such interactions, we develop a
model that predicts individual A's opinion of individual B by synthesizing
information from the signed social network in which A and B are embedded with
sentiment analysis of the evaluative texts relating A to B. We prove that this
problem is NP-hard but can be relaxed to an efficiently solvable hinge-loss
Markov random field, and we show that this implementation outperforms text-only
and network-only versions in two very different datasets involving
community-level decision-making: the Wikipedia Requests for Adminship corpus
and the Convote U.S. Congressional speech corpus
Recursive Online Enumeration of All Minimal Unsatisfiable Subsets
In various areas of computer science, we deal with a set of constraints to be
satisfied. If the constraints cannot be satisfied simultaneously, it is
desirable to identify the core problems among them. Such cores are called
minimal unsatisfiable subsets (MUSes). The more MUSes are identified, the more
information about the conflicts among the constraints is obtained. However, a
full enumeration of all MUSes is in general intractable due to the large number
(even exponential) of possible conflicts. Moreover, to identify MUSes
algorithms must test sets of constraints for their simultaneous satisfiabilty.
The type of the test depends on the application domains. The complexity of
tests can be extremely high especially for domains like temporal logics, model
checking, or SMT. In this paper, we propose a recursive algorithm that
identifies MUSes in an online manner (i.e., one by one) and can be terminated
at any time. The key feature of our algorithm is that it minimizes the number
of satisfiability tests and thus speeds up the computation. The algorithm is
applicable to an arbitrary constraint domain and its effectiveness demonstrates
itself especially in domains with expensive satisfiability checks. We benchmark
our algorithm against state of the art algorithm on Boolean and SMT constraint
domains and demonstrate that our algorithm really requires less satisfiability
tests and consequently finds more MUSes in given time limits
Computing Possible and Certain Answers over Order-Incomplete Data
This paper studies the complexity of query evaluation for databases whose
relations are partially ordered; the problem commonly arises when combining or
transforming ordered data from multiple sources. We focus on queries in a
useful fragment of SQL, namely positive relational algebra with aggregates,
whose bag semantics we extend to the partially ordered setting. Our semantics
leads to the study of two main computational problems: the possibility and
certainty of query answers. We show that these problems are respectively
NP-complete and coNP-complete, but identify tractable cases depending on the
query operators or input partial orders. We further introduce a duplicate
elimination operator and study its effect on the complexity results.Comment: 55 pages, 56 references. Extended journal version of
arXiv:1707.07222. Up to the stylesheet, page/environment numbering, and
possible minor publisher-induced changes, this is the exact content of the
journal paper that will appear in Theoretical Computer Scienc
From outer circle to center stage: The maturation of heterodox economics
This is chapter 2 of the book "Future Directions in Heterodox Economics" by John T. Harvey and Robert F. Garnett, Jr., Editors. The inner circle of neoclassical economics has limited its horizons, increasing the scope for heterodox economists to claim ever more of the most important issues. Two values contend for primacy: being scientific, and being relevant. These need not—and should not—be in conflict; an important goal for economics in the future is to bring them into better harmony.Heterodox economics, contextual economics, neoclassical theory, economic goals, history of economic thought
Validation of Simulation: Patterns in the Social and Natural Sciences
In most cases, the meaning of computer simulation is strongly connected to the idea numerical calculations. A computer simulation is a numerical solution of a complex mathematical problem. Therefore, the problem of validation of its results should be only a problem of judging the underlying computational methods. However, it will be argued, that this is not the case. It is consensus in literature that validation constitutes one of the central epistemological problems of computer simulation methods. Especially in the case of simulations in the social sciences the answers given by many authors are not satisfactory. The following paper attempts to show how the characteristics of simulation, i.e. the imitation of a dynamic, constitute the problem of validation even in the case of the natural sciences and what consequences arise. Differences as well as common grounds between social and natural sciences will be discussed.Generative Mechanism, Imitation, Patterns, Simulation, Validation
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