362 research outputs found
Lending Petri nets and contracts
Choreography-based approaches to service composition typically assume that,
after a set of services has been found which correctly play the roles
prescribed by the choreography, each service respects his role. Honest services
are not protected against adversaries. We propose a model for contracts based
on a extension of Petri nets, which allows services to protect themselves while
still realizing the choreography. We relate this model with Propositional
Contract Logic, by showing a translation of formulae into our Petri nets which
preserves the logical notion of agreement, and allows for compositional
verification
Maude: specification and programming in rewriting logic
Maude is a high-level language and a high-performance system supporting executable specification and declarative programming in rewriting logic. Since rewriting logic contains equational logic, Maude also supports equational specification and programming in its sublanguage of functional modules and theories. The underlying equational logic chosen for Maude is membership equational logic, that has sorts, subsorts, operator overloading, and partiality definable by membership and equality conditions. Rewriting logic is reflective, in the sense of being able to express its own metalevel at the object level. Reflection is systematically exploited in Maude endowing the language with powerful metaprogramming capabilities, including both user-definable module operations and declarative strategies to guide the deduction process. This paper explains and illustrates with examples the main concepts of Maude's language design, including its underlying logic, functional, system and object-oriented modules, as well as parameterized modules, theories, and views. We also explain how Maude supports reflection, metaprogramming and internal strategies. The paper outlines the principles underlying the Maude system implementation, including its semicompilation techniques. We conclude with some remarks about applications, work on a formal environment for Maude, and a mobile language extension of Maude
An exponential chemorheological model for viscosity dependence on degree-of-cure of a polyfurfuryl alcohol resin during the post-gel curing stage
La regeneración del pinsapar en la sierra de Grazalema. I: análisis de la fase de plántula
Se estudia la dinámica de la regeneración del pinsapar en la Sierra de Grazalema. Previamente
se ha llevado a cabo una diferenciación del conjunto del pinsapar a partir de la información disponible
de inventarios, fotointerpretación, bibliografía y datos de campo, dando como resultados cuatro
tipos estructurales: Pinsapar puro estructurado, Pinsapar puro latizal-fustal, Quejigal con pinsapos
y Encinar con pinsapos. En este estudio, el análisis del proceso de regeneración se centra en el
regenerado en estado de plántula, donde la mortalidad puede tener una incidencia enorme debida
especialmente a la sequía estival propia del ámbito mediterráneo. Se ha establecido un dispositivo
de muestreo sistemático en los cuatro estratos, medido una vez finalizada la germinación de semillas
del año y después del verano. Con los datos obtenidos se ha estudiado tanto la incorporación,
como la mortalidad de nuevas plántulas. Se han encontrado diferencias significativas entre los estratos
de pinsapar puro y los mixtos, tanto en incorporación de nuevas plántulas como en mortalidad.
También existen diferencias dentro de los dos estratos de pinsapar pur
La regeneración del pinsapar en la sierra de Grazalema. II: estructura y dinámica del regenerado consolidado en el pinsapar puro
En los tipos estructurales de pinsapar puro, se estudia la dinámica y la estructura del regenerado
consolidado (plantas de más de un año de edad que no alcanzan las dimensiones de los pies menores,
es decir, menos de 1,5 m de altura). El motivo de separar este grupo del de plántulas menores
de un año, estriba en las diferentes posibilidades de supervivencia de uno y otro estado ya que en el
regenerado consolidado va a depender en mayor medida del grado de competencia al que se vea
sometido que de las condiciones locales del medio en que se asienta. El análisis de la distribución
de alturas por clases muestra importantes diferencias significativas entre ambos estratos de pinsapar
puro, para la clase < 15 cm pero no para las demás clases. Se ha analizado la evolución de la densidad
del regenerado por clases de altura desde la fase de plántula hasta la de pie menor, obteniendo
una gráfica descendente similar en ambos estratos con una caída brusca inexplicada en la clase de
100 a 150 cm, seguida de una subida en la clase de pies menores atribuida al estancamiento en el
crecimiento en altura. El estudio de la relación altura edad demuestra que ésta es significativa, para
el regenerado, pero no para los pies menores, indicando así que este grupo se compone de árboles
dominados de numerosas y muy distintas edades. El regenerado consolidado constituye una reserva
de regeneración a la espera, cuyos individuos aprovecharían las perturbaciones en la estructura para
prosperar. Puede decirse que en las circunstancias actuales y frente a perturbaciones no catastróficas,
la persistencia del pinsapar está asegurad
Debugging of Web Applications with Web-TLR
Web-TLR is a Web verification engine that is based on the well-established
Rewriting Logic--Maude/LTLR tandem for Web system specification and
model-checking. In Web-TLR, Web applications are expressed as rewrite theories
that can be formally verified by using the Maude built-in LTLR model-checker.
Whenever a property is refuted, a counterexample trace is delivered that
reveals an undesired, erroneous navigation sequence. Unfortunately, the
analysis (or even the simple inspection) of such counterexamples may be
unfeasible because of the size and complexity of the traces under examination.
In this paper, we endow Web-TLR with a new Web debugging facility that supports
the efficient manipulation of counterexample traces. This facility is based on
a backward trace-slicing technique for rewriting logic theories that allows the
pieces of information that we are interested to be traced back through inverse
rewrite sequences. The slicing process drastically simplifies the computation
trace by dropping useless data that do not influence the final result. By using
this facility, the Web engineer can focus on the relevant fragments of the
failing application, which greatly reduces the manual debugging effort and also
decreases the number of iterative verifications.Comment: In Proceedings WWV 2011, arXiv:1108.208
Maude: specification and programming in rewriting logic
AbstractMaude is a high-level language and a high-performance system supporting executable specification and declarative programming in rewriting logic. Since rewriting logic contains equational logic, Maude also supports equational specification and programming in its sublanguage of functional modules and theories. The underlying equational logic chosen for Maude is membership equational logic, that has sorts, subsorts, operator overloading, and partiality definable by membership and equality conditions. Rewriting logic is reflective, in the sense of being able to express its own metalevel at the object level. Reflection is systematically exploited in Maude endowing the language with powerful metaprogramming capabilities, including both user-definable module operations and declarative strategies to guide the deduction process. This paper explains and illustrates with examples the main concepts of Maude's language design, including its underlying logic, functional, system and object-oriented modules, as well as parameterized modules, theories, and views. We also explain how Maude supports reflection, metaprogramming and internal strategies. The paper outlines the principles underlying the Maude system implementation, including its semicompilation techniques. We conclude with some remarks about applications, work on a formal environment for Maude, and a mobile language extension of Maude
Synaptic and extrasynaptic NMDA receptors are gated by different endogenous coagonists.
N-methyl-D-aspartate receptors (NMDARs) are located in neuronal cell membranes at synaptic and extrasynaptic locations, where they are believed to mediate distinct physiological and pathological processes. Activation of NMDARs requires glutamate and a coagonist whose nature and impact on NMDAR physiology remain elusive. We report that synaptic and extrasynaptic NMDARs are gated by different endogenous coagonists, D-serine and glycine, respectively. The regionalized availability of the coagonists matches the preferential affinity of synaptic NMDARs for D-serine and extrasynaptic NMDARs for glycine. Furthermore, glycine and D-serine inhibit NMDAR surface trafficking in a subunit-dependent manner, which is likely to influence NMDARs subcellular location. Taking advantage of this coagonist segregation, we demonstrate that long-term potentiation and NMDA-induced neurotoxicity rely on synaptic NMDARs only. Conversely, long-term depression requires both synaptic and extrasynaptic receptors. Our observations provide key insights into the operating mode of NMDARs, emphasizing functional distinctions between synaptic and extrasynaptic NMDARs in brain physiology
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