234 research outputs found
Modeling a Language for Embedded Systems in Timed Automata
We present a compositional method for translating real-timeprograms into networks of timed automata. Programs are written in anassembly like real-time language and translated into models supportedby the tool Uppaal. We have implemented the translation and give anexample of its application on a simple control program for a car. Someproperties of the behavior of the control program are verified using thegenerated model
New systems for heterogeneous catalytic epoxidation
Epoxides are very useful key intermediates in the construction of synthetically
challenging molecules. Owing to their strategic importance in organic synthesis, novel
polymer-supported iminium salts were investigated for the catalytic oxidation of
unfunctionalised alkenes. A solid-phase methodology was initiated and then developed for
the evaluation of several heterogeneous catalysts.
In an initial approach, immobilised iminium salts were prepared by condensation of
2-(bromoethyl)benzaldehyde with commercially available aminomethyl resins. These
materials were shown to be able to successfully catalyse the epoxidation of 1-phenylcyclohexene. The epoxidation reactions were performed in a triphasic system using
Oxone® as the oxidising agent and 25 mol% of the catalyst. For all the resin type
employed, namely NovaSyn TG, NovaGel, ArgoGel or PEGA, complete conversion of the
alkenes to their respective epoxides was obtained. [Continues.
Processing SPARQL queries with regular expressions in RDF databases
Background: As the Resource Description Framework (RDF) data model is widely used for modeling and sharing a lot of online bioinformatics resources such as Uniprot (dev.isb-sib.ch/projects/uniprot-rdf) or Bio2RDF (bio2rdf.org), SPARQL - a W3C recommendation query for RDF databases - has become an important query language for querying the bioinformatics knowledge bases. Moreover, due to the diversity of users' requests for extracting information from the RDF data as well as the lack of users' knowledge about the exact value of each fact in the RDF databases, it is desirable to use the SPARQL query with regular expression patterns for querying the RDF data. To the best of our knowledge, there is currently no work that efficiently supports regular expression processing in SPARQL over RDF databases. Most of the existing techniques for processing regular expressions are designed for querying a text corpus, or only for supporting the matching over the paths in an RDF graph.
Results: In this paper, we propose a novel framework for supporting regular expression processing in SPARQL query. Our contributions can be summarized as follows. 1) We propose an efficient framework for processing SPARQL queries with regular expression patterns in RDF databases. 2) We propose a cost model in order to adapt the proposed framework in the existing query optimizers. 3) We build a prototype for the proposed framework in C++ and conduct extensive experiments demonstrating the efficiency and effectiveness of our technique.
Conclusions: Experiments with a full-blown RDF engine show that our framework outperforms the existing ones by up to two orders of magnitude in processing SPARQL queries with regular expression patterns.X113sciescopu
Using Model 204 Databse Management System to Build a Computer Assited Test Construction System for a Fortran Course
Linear Parametric Model Checking of Timed Automata
We present an extension of the model checker Uppaal capable of synthesizing linear parameter constraints for the correctness ofparametric timed automata. The symbolic representation of the (parametric) state-space is shown to be correct. A second contribution of thispaper is the identification of a subclass of parametric timed automata(L/U automata), for which the emptiness problem is decidable, contraryto the full class where it is know to be undecidable. Also we present anumber of lemmas enabling the verification effort to be reduced for L/Uautomata in some cases. We illustrate our approach by deriving linearparameter constraints for a number of well-known case studies from theliterature (exhibiting a flaw in a published paper)
Language Emptiness of Continuous-Time Parametric Timed Automata
Parametric timed automata extend the standard timed automata with the
possibility to use parameters in the clock guards. In general, if the
parameters are real-valued, the problem of language emptiness of such automata
is undecidable even for various restricted subclasses. We thus focus on the
case where parameters are assumed to be integer-valued, while the time still
remains continuous. On the one hand, we show that the problem remains
undecidable for parametric timed automata with three clocks and one parameter.
On the other hand, for the case with arbitrary many clocks where only one of
these clocks is compared with (an arbitrary number of) parameters, we show that
the parametric language emptiness is decidable. The undecidability result
tightens the bounds of a previous result which assumed six parameters, while
the decidability result extends the existing approaches that deal with
discrete-time semantics only. To the best of our knowledge, this is the first
positive result in the case of continuous-time and unbounded integer
parameters, except for the rather simple case of single-clock automata
LTL Parameter Synthesis of Parametric Timed Automata
The parameter synthesis problem for parametric timed automata is undecidable
in general even for very simple reachability properties. In this paper we
introduce restrictions on parameter valuations under which the parameter
synthesis problem is decidable for LTL properties. The investigated bounded
integer parameter synthesis problem could be solved using an explicit
enumeration of all possible parameter valuations. We propose an alternative
symbolic zone-based method for this problem which results in a faster
computation. Our technique extends the ideas of the automata-based approach to
LTL model checking of timed automata. To justify the usefulness of our
approach, we provide experimental evaluation and compare our method with
explicit enumeration technique.Comment: 23 pages, extended versio
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