3,384 research outputs found
A Compass to Controlled Graph Rewriting
With the growing complexity and autonomy of software-intensive systems, abstract modeling to study and formally analyze those systems is gaining on importance. Graph rewriting is an established, theoretically founded formalism for the graphical modeling of structure and behavior of complex systems. A graph-rewriting system consists of declarative rules, providing templates for potential changes in the modeled graph structures over time. Nowadays complex software systems, often involving distributedness and, thus, concurrency and reactive behavior, pose a challenge to the hidden assumption of global knowledge behind graph-based modeling; in particular, describing their dynamics by rewriting rules often involves a need for additional control to reflect algorithmic system aspects. To that end, controlled graph rewriting has been proposed, where an external control language guides the sequence in which rules are applied. However, approaches elaborating on this idea so far either have a practical, implementational focus without elaborating on formal foundations, or a pure input-output semantics without further considering concurrent and reactive notions.
In the present thesis, we propose a comprehensive theory for an operational semantics of controlled graph rewriting, based on well-established notions from the theory of process calculi. In the first part, we illustrate the aforementioned fundamental phenomena by means of a simplified model of wireless sensor networks (WSN). After recapitulating the necessary background on DPO graph rewriting, the formal framework used throughout the thesis, we present an extensive survey on the state of the art in controlled graph rewriting, along the challenges which we address in the second part where we elaborate our theoretical contributions. As a novel approach, we propose a process calculus for controlled graph rewriting, called RePro, where DPO rule applications are controlled by process terms closely resembling the process calculus CCS. In particular, we address the aforementioned challenges: (i) we propose a formally founded control language for graph rewriting with an operational semantics, (ii) explicitly addressing concurrency and reactive behavior in system modeling, (iii) allowing for a proper handling of process equivalence and action independence using process-algebraic notions.
Finally, we present a novel abstract verification approach for graph rewriting based on abstract interpretation of reactive systems. To that end, we propose the so-called compasses as an abstract representation of infinite graph languages and demonstrate their use for the verification of process properties over infinite input sets
Confluence Detection for Transformations of Labelled Transition Systems
The development of complex component software systems can be made more
manageable by first creating an abstract model and then incrementally adding
details. Model transformation is an approach to add such details in a
controlled way. In order for model transformation systems to be useful, it is
crucial that they are confluent, i.e. that when applied on a given model, they
will always produce a unique output model, independent of the order in which
rules of the system are applied on the input. In this work, we consider
Labelled Transition Systems (LTSs) to reason about the semantics of models, and
LTS transformation systems to reason about model transformations. In related
work, the problem of confluence detection has been investigated for general
graph structures. We observe, however, that confluence can be detected more
efficiently in special cases where the graphs have particular structural
properties. In this paper, we present a number of observations to detect
confluence of LTS transformation systems, and propose both a new confluence
detection algorithm and a conflict resolution algorithm based on them.Comment: In Proceedings GaM 2015, arXiv:1504.0244
Sparse Linear Identifiable Multivariate Modeling
In this paper we consider sparse and identifiable linear latent variable
(factor) and linear Bayesian network models for parsimonious analysis of
multivariate data. We propose a computationally efficient method for joint
parameter and model inference, and model comparison. It consists of a fully
Bayesian hierarchy for sparse models using slab and spike priors (two-component
delta-function and continuous mixtures), non-Gaussian latent factors and a
stochastic search over the ordering of the variables. The framework, which we
call SLIM (Sparse Linear Identifiable Multivariate modeling), is validated and
bench-marked on artificial and real biological data sets. SLIM is closest in
spirit to LiNGAM (Shimizu et al., 2006), but differs substantially in
inference, Bayesian network structure learning and model comparison.
Experimentally, SLIM performs equally well or better than LiNGAM with
comparable computational complexity. We attribute this mainly to the stochastic
search strategy used, and to parsimony (sparsity and identifiability), which is
an explicit part of the model. We propose two extensions to the basic i.i.d.
linear framework: non-linear dependence on observed variables, called SNIM
(Sparse Non-linear Identifiable Multivariate modeling) and allowing for
correlations between latent variables, called CSLIM (Correlated SLIM), for the
temporal and/or spatial data. The source code and scripts are available from
http://cogsys.imm.dtu.dk/slim/.Comment: 45 pages, 17 figure
Proceedings of International Workshop "Global Computing: Programming Environments, Languages, Security and Analysis of Systems"
According to the IST/ FET proactive initiative on GLOBAL COMPUTING, the goal is to obtain techniques (models, frameworks, methods, algorithms) for constructing systems that are flexible, dependable, secure, robust and efficient.
The dominant concerns are not those of representing and manipulating data efficiently but rather those of handling the co-ordination and interaction, security, reliability, robustness, failure modes, and control of risk of the entities in the system and the overall design, description and performance of the system itself.
Completely different paradigms of computer science may have to be developed to tackle these issues effectively. The research should concentrate on systems having the following characteristics: • The systems are composed of autonomous computational entities where activity is not centrally controlled, either because global control is impossible or impractical, or because the entities are created or controlled by different owners.
• The computational entities are mobile, due to the movement of the physical platforms or by movement of the entity from one platform to another.
• The configuration varies over time. For instance, the system is open to the introduction of new computational entities and likewise their deletion.
The behaviour of the entities may vary over time.
• The systems operate with incomplete information about the environment.
For instance, information becomes rapidly out of date and mobility requires information about the environment to be discovered.
The ultimate goal of the research action is to provide a solid scientific foundation for the design of such systems, and to lay the groundwork for achieving effective principles for building and analysing such systems.
This workshop covers the aspects related to languages and programming environments as well as analysis of systems and resources involving 9 projects (AGILE , DART, DEGAS , MIKADO, MRG, MYTHS, PEPITO, PROFUNDIS, SECURE) out of the 13 founded under the initiative. After an year from the start of the projects, the goal of the workshop is to fix the state of the art on the topics covered by the two clusters related to programming environments and analysis of systems as well as to devise strategies and new ideas to profitably continue the research effort towards the overall objective of the initiative.
We acknowledge the Dipartimento di Informatica and Tlc of the University of Trento, the Comune di Rovereto, the project DEGAS for partially funding the event and the Events and Meetings Office of the University of Trento for the valuable collaboration
The Mathematical Abstraction Theory, The Fundamentals for Knowledge Representation and Self-Evolving Autonomous Problem Solving Systems
The intention of the present study is to establish the mathematical
fundamentals for automated problem solving essentially targeted for robotics by
approaching the task universal algebraically introducing knowledge as
realizations of generalized free algebra based nets, graphs with gluing forms
connecting in- and out-edges to nodes. Nets are caused to undergo
transformations in conceptual level by type wise differentiated intervening net
rewriting systems dispersing problems to abstract parts, matching being
determined by substitution relations. Achieved sets of conceptual nets
constitute congruent classes. New results are obtained within construction of
problem solving systems where solution algorithms are derived parallel with
other candidates applied to the same net classes. By applying parallel
transducer paths consisting of net rewriting systems to net classes congruent
quotient algebras are established and the manifested class rewriting comprises
all solution candidates whenever produced nets are in anticipated languages
liable to acceptance of net automata. Furthermore new solutions will be added
to the set of already known ones thus expanding the solving power in the
forthcoming. Moreover special attention is set on universal abstraction,
thereof generation by net block homomorphism, consequently multiple order
solving systems and the overall decidability of the set of the solutions. By
overlapping presentation of nets new abstraction relation among nets is
formulated alongside with consequent alphabetical net block renetting system
proportional to normal forms of renetting systems regarding the operational
power. A new structure in self-evolving problem solving is established via
saturation by groups of equivalence relations and iterative closures of
generated quotient transducer algebras over the whole evolution.Comment: This article is a part of my thesis giving the unity for both
knowledge presentation and self-evolution in autonomous problem solving
mathematical systems and for that reason draws heavily from my previous work
arxiv:1305.563
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