81,871 research outputs found
Rewriting-based Verification and Debugging of Web Systems
The increasing complexity of Web system has led to the development of sophisticated formal methodologies for verifying and correcting Web data and Web programs.
In general, establishing whether a Web system behaves correctly with respect to the original intention of the programmer or checking its internal consistency
are non-trivial tasks as witnessed by many studies in the literature.
In this dissertation, we face two challenging problems related to the verification of Web systems.
Firstly, we extend a previous Web verification framework based on partial rewriting by providing a semi-automatic technique for repairing Web systems.
We propose a basic repairing methodology that is endowed with several strategies for optimizing the number of repair actions that must be executed in order to fix a given Web site.
Also, we develop an improvement of the Web verification framework that is based on abstract interpretation and greatly enhances both efficiency and scalability of the original technique.
Secondly, we formalize a framework for the specification and model-checking of dynamic Web applications that is based on Rewriting Logic.
Our framework allows one to simulate
the user navigation and the evaluation of Web scripts within a Web application, and also check important related properties such us reachability and consistency.
When a property is refuted, a counter-example with the erroneous trace is delivered.
Such information can be analyzed in order to debug the Web application under examination by means of a novel backward trace slicing technique that we formulated for this purpose.
This technique consists in tracing back, along an execution trace, all the relevant symbols of the term (or state) that we are interested to observe.Romero ., DO. (2011). Rewriting-based Verification and Debugging of Web Systems [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/12496Palanci
Forward Analysis and Model Checking for Trace Bounded WSTS
We investigate a subclass of well-structured transition systems (WSTS), the
bounded---in the sense of Ginsburg and Spanier (Trans. AMS 1964)---complete
deterministic ones, which we claim provide an adequate basis for the study of
forward analyses as developed by Finkel and Goubault-Larrecq (Logic. Meth.
Comput. Sci. 2012). Indeed, we prove that, unlike other conditions considered
previously for the termination of forward analysis, boundedness is decidable.
Boundedness turns out to be a valuable restriction for WSTS verification, as we
show that it further allows to decide all -regular properties on the
set of infinite traces of the system
Model-Checking Process Equivalences
Process equivalences are formal methods that relate programs and system
which, informally, behave in the same way. Since there is no unique notion of
what it means for two dynamic systems to display the same behaviour there are a
multitude of formal process equivalences, ranging from bisimulation to trace
equivalence, categorised in the linear-time branching-time spectrum.
We present a logical framework based on an expressive modal fixpoint logic
which is capable of defining many process equivalence relations: for each such
equivalence there is a fixed formula which is satisfied by a pair of processes
if and only if they are equivalent with respect to this relation. We explain
how to do model checking, even symbolically, for a significant fragment of this
logic that captures many process equivalences. This allows model checking
technology to be used for process equivalence checking. We show how partial
evaluation can be used to obtain decision procedures for process equivalences
from the generic model checking scheme.Comment: In Proceedings GandALF 2012, arXiv:1210.202
Adaptive Homing is in P
Homing preset and adaptive experiments with Finite State Machines (FSMs) are
widely used when a non-initialized discrete event system is given for testing
and thus, has to be set to the known state at the first step. The length of a
shortest homing sequence is known to be exponential with respect to the number
of states for a complete observable nondeterministic FSM while the problem of
checking the existence of such sequence (Homing problem) is PSPACE-complete. In
order to decrease the complexity of related problems, one can consider adaptive
experiments when a next input to be applied to a system under experiment
depends on the output responses to the previous inputs. In this paper, we study
the problem of the existence of an adaptive homing experiment for complete
observable nondeterministic machines. We show that if such experiment exists
then it can be constructed with the use of a polynomial-time algorithm with
respect to the number of FSM states.Comment: In Proceedings MBT 2015, arXiv:1504.0192
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Software integration testing based on communication coverage criteria and partial model generation
This paper considers the problem of integration testing the components of a timed distributed software system. We assume that communication between the components is specified using timed interface automata and use computational tree logic (CTL) to define communication-based coverage criteria that refer to send- and receive-statements and communication paths. The proposed method enables testers to focus during component integration on such parts of the specification, e.g. behaviour specifications or Markovian usage models, that are involved in the communication between components to be integrated. A more specific application area of this approach is the integration of test-models, e.g. a transmission gear can be tested based on separated models for the driver behaviour, the engine condition, and the mechanical and hydraulical transmission states. Given such a state-based specification of a distributed system and a concrete coverage goal, a model checker is used in order to determine the coverage or generate test sequences that achieve the goal. Given the generated test sequences we derive a partial test-model of the components from which the test sequences are derived. The partial model can be used to drive further testing and can also be used as the basis for producing additional partial models in incremental integration testing. While the process of deriving the test sequences could suffer from a combinatorial explosion, the effort required to generate the partial model is polynomial in the number of test sequences and their length. Thus, where it is not feasible to produce test sequences that achieve a given type of coverage it is still possible to produce a partial model on the basis of test sequences generated to achieve some other criterion. As a result, the process of generating a partial model has the potential to scale to large industrial software systems. While a particular model checker, UPPAAL, was used, it should be relatively straightforward to adapt the approach for use with other CTL based model checkers. A potential additional benefit of the approach is that it provides a visual description of the state-based testing of distributed systems, which may be beneficial in other contexts such as education and comprehension
Interference Alignment for Partially Connected MIMO Cellular Networks
In this paper, we propose an iterative interference alignment (IA) algorithm
for MIMO cellular networks with partial connectivity, which is induced by
heterogeneous path losses and spatial correlation. Such systems impose several
key technical challenges in the IA algorithm design, namely the overlapping
between the direct and interfering links due to the MIMO cellular topology as
well as how to exploit the partial connectivity. We shall address these
challenges and propose a three stage IA algorithm. As illustration, we analyze
the achievable degree of freedom (DoF) of the proposed algorithm for a
symmetric partially connected MIMO cellular network. We show that there is
significant DoF gain compared with conventional IA algorithms due to partial
connectivity. The derived DoF bound is also backward compatible with that
achieved on fully connected K-pair MIMO interference channels.Comment: Submitted to IEEE Transactions on Signal Processing, accepte
Controllability in partial and uncertain environments
© 2014 IEEE.Controller synthesis is a well studied problem that attempts to automatically generate an operational behaviour model of the system-to-be that satisfies a given goal when deployed in a given domain model that behaves according to specified assumptions. A limitation of many controller synthesis techniques is that they require complete descriptions of the problem domain. This is limiting in the context of modern incremental development processes when a fully described problem domain is unavailable, undesirable or uneconomical. Previous work on Modal Transition Systems (MTS) control problems exists, however it is restricted to deterministic MTSs and deterministic Labelled Transition Systems (LTS) implementations. In this paper we study the Modal Transition System Control Problem in its full generality, allowing for nondeterministic MTSs modelling the environments behaviour and nondeterministic LTS implementations. Given an nondeterministic MTS we ask if all, none or some of the nondeterministic LTSs it describes admit an LTS controller that guarantees a given property. We show a technique that solves effectively the MTS realisability problem and it can be, in some cases, reduced to deterministic control problems. In all cases the MTS realisability problem is in same complexity class as the corresponding LTS problem
Model checking quantum Markov chains
Although the security of quantum cryptography is provable based on the
principles of quantum mechanics, it can be compromised by the flaws in the
design of quantum protocols and the noise in their physical implementations.
So, it is indispensable to develop techniques of verifying and debugging
quantum cryptographic systems. Model-checking has proved to be effective in the
verification of classical cryptographic protocols, but an essential difficulty
arises when it is applied to quantum systems: the state space of a quantum
system is always a continuum even when its dimension is finite. To overcome
this difficulty, we introduce a novel notion of quantum Markov chain, specially
suited to model quantum cryptographic protocols, in which quantum effects are
entirely encoded into super-operators labelling transitions, leaving the
location information (nodes) being classical. Then we define a quantum
extension of probabilistic computation tree logic (PCTL) and develop a
model-checking algorithm for quantum Markov chains.Comment: Journal versio
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