963 research outputs found
Formalization and Correctness of the PALS Architectural Pattern for Distributed Real-Time Systems
Many Distributed Real-Time Systems (DRTS), such as integrated modular avionics systems and distributed control systems in
motor vehicles, are made up of a collection of components communicating asynchronously among themselves and with their environment
that must change their state and respond to environment inputs within
hard real-time bounds. Such systems are often safety-critical and need
to be certi???ed; but their certi???cation is currently very hard due to their
distributed nature. The Physically Asynchronous Logically Synchronous
(PALS) architectural pattern can greatly reduce the design and veri???cation complexities of achieving virtual synchrony in a DTRS. This work
presents a formal speci???cation of PALS as a formal model transformation that maps a synchronous design, together with a set of performance
bounds of the underlying infrastructure, to a formal DRTS speci???cation
that is semantically equivalent to the synchronous design. This semantic
equivalence is proved, showing that the formal veri???cation of temporal
logic properties of the DRTS can be reduced to their veri???cation on the
much simpler synchronous design. An avionics system case study is used
to illustrate the usefulness of PALS for formal verification purposes.unpublishednot peer reviewe
Towards Generic Monitors for Object-Oriented Real-Time Maude Specifications
Non-Functional Properties (NFPs) are crucial in the design of software. Specification of systems is used in the very first phases of the software development process for the stakeholders to make decisions on which architecture or platform to use. These specifications may be an- alyzed using different formalisms and techniques, simulation being one of them. During a simulation, the relevant data involved in the anal- ysis of the NFPs of interest can be measured using monitors. In this work, we show how monitors can be parametrically specified so that the instrumentation of specifications to be monitored can be automatically performed. We prove that the original specification and the automati- cally obtained specification with monitors are bisimilar by construction. This means that the changes made on the original system by adding monitors do not affect its behavior. This approach allows us to have a library of possible monitors that can be safely added to analyze different properties, possibly on different objects of our systems, at will.Universidad de Málaga, Campus de Excelencia Internacional Andalucía Tech. Spanish MINECO/FEDER project TIN2014-52034-R, NSF Grant CNS 13-19109
State space c-reductions for concurrent systems in rewriting logic
We present c-reductions, a state space reduction technique.
The rough idea is to exploit some equivalence relation on states (possibly capturing system regularities) that preserves behavioral properties, and explore the induced quotient system. This is done by means of a canonizer
function, which maps each state into a (non necessarily unique) canonical representative of its equivalence class. The approach exploits the expressiveness of rewriting logic and its realization in Maude to enjoy several advantages over similar approaches: exibility and simplicity in
the definition of the reductions (supporting not only traditional symmetry reductions, but also name reuse and name abstraction); reasoning support for checking and proving correctness of the reductions; and automatization
of the reduction infrastructure via Maude's meta-programming
features. The approach has been validated over a set of representative case studies, exhibiting comparable results with respect to other tools
Evaluating the performance of model transformation styles in Maude
Rule-based programming has been shown to be very successful in many application areas. Two prominent examples are the specification of model transformations in model driven development approaches and the definition of structured operational semantics of formal languages. General rewriting frameworks such as Maude are flexible enough to allow the programmer to adopt and mix various rule styles. The choice between styles can be biased by the programmer’s background. For instance, experts in visual formalisms might prefer graph-rewriting styles, while experts in semantics might prefer structurally inductive rules. This paper evaluates the performance of different rule styles on a significant benchmark taken from the literature on model transformation. Depending on the actual transformation being carried out, our results show that different rule styles can offer drastically different performances. We point out the situations from which each rule style benefits to offer a valuable set of hints for choosing one style over the other
One-dimensional dynamics of nearly unstable axisymmetric liquid bridges
A general one-dimensional model is considered that describes the dynamics of slender, axisymmetric, noncylindrical liquid bridges between two equal disks. Such model depends on two adjustable parameters and includes as particular cases the standard Lee and Cosserat models. For slender liquid bridges, the model provides sufficiently accurate results and involves much easier and faster calculations than the full three-dimensional model. In particular, viscous effects are easily accounted for. The one-dimensional model is used to derive a simple weakly nonlinear description of the dynamics near the instability limit. Small perturbations of marginal instability conditions are also considered that account for volume perturbations, nonequality of the supporting disks, and axial gravity. The analysis shows that the dynamics breaks the reflection symmetry on the midplane between the supporting disks. The weakly nonlinear evolution of the amplitude of the perturbation is given by a Duffing equation, whose coefficients are calculated in terms of the slenderness as a part of the analysis and exhibit a weak dependence on the adjustable parameters of the one-dimensional model. The amplitude equation is used to make quantitative predictions of both the (first stage of) breakage for unstable configurations and the (slow) dynamics for stable configurations
Growth and formation of inverse GaP and InP opals
Opals consist of an ordered array of SiO2 spheres. This leads to a modulation of the refractive index and hence photonic stop bands behaviour over the visible/IR range of the electro-magnetic spectrum. The exact position of the stop bands depends on the size of the silica spheres. However, the refractive index contrast between the SiO2 spheres and air spaces is not great enough to open up a full photonic band gap (PBG), only the pseudogap. To increase the contrast the air spaces are filled with a material of high refractive index such as InP or GaP. To further increase the contrast the SiO2 is removed leaving a III-V framework as the inverse opal structure.
By use of MOCVD we have been able to infill opals with InP and GaP to such a level that has supported the inversion of the composite forming a structure of air holes within a III-V lattice. XRD and Raman confirmed the quality of the III-V infill, while the extent of the infill was studied by SEM and reflectance measurements
Rewriting Semantics of Meta-Objects and Composable Distributed Services1 1Supported by DARPA through Rome Laboratories Contract F30602-97-C-0312, by DARPA and NASA through Contract NAS2-98073, by Office of Naval Research Contract N00014-99-C-0198, and by National Science Foundation Grants CCR-9505960 and CCR-9633363, and CCR-9900334.
AbstractCommunication between distributed objects may have to be protected against random failures and malicious attacks; also, communication timeliness may be essential or highly desired. Therefore, a distributed application often has to be extended with communication services providing some kind of fault-tolerance, secrecy, or quality-of-service guarantees. Ideally, such services should be defined in a highly modular and dynamically composable way, so that the combined assurance of several services can be achieved by composition in certain cases, and so that services can be added or removed from applications at runtime in response to changes in the environment. To reason about the formal properties of such composable communication services one first needs to give them a precise semantics. This paper proposes a rewriting logic semantics for the so-called “onion skin” model of distributed object reflection, in which different meta-objects, providing different communication services, can be stacked on top of a basic application object. Since the correct behavior of a service depends on the type of hostile environment, against which the service must protect the application, rewriting logic should also be used to specify such hostile environments. The service guarantees are then guarantees about the behavior specified by the union of the rewrite theories specifying the basic application, the services, and the hostile environment
Diacritical study of light, electrons, and sound scattering by particles and holes
We discuss the differences and similarities in the interaction of scalar and
vector wave-fields with particles and holes. Analytical results are provided
for the transmission of isolated and arrayed small holes as well as surface
modes in hole arrays for light, electrons, and sound. In contrast to the
optical case, small-hole arrays in perforated perfect screens cannot produce
acoustic or electronic surface-bound states. However, unlike electrons and
light, sound is transmitted through individual holes approximately in
proportion to their area, regardless their size. We discuss these issues with a
systematic analysis that allows exploring both common properties and unique
behavior in wave phenomena for different material realizations.Comment: 3 figure
Analysis of the feeding system in the injection process of peek in fixed partial dentures
[EN] In dental sector, PEEK is a new material used in the injection process of fixed partial dentures (FPD). The design of the feeding system is one of the most important stages in the injection process. This study simulates different locations of the feeding system in fixed partial dentures of PEEK, varying number of the injection points, using the software Moldflow. Variables used to compare simulations are the complete filling of the FPD mould cavity, the filling time, the minimum amount of rejected material of the feeding system, defects due to air traps, welding lines, etc. As results, depending on the geometric complexity, and the number and position of the injection points, it is possible to reduce the rejected material and to improve the filling time of the FPD.Gutiérrez, SC.; Meseguer, MD.; Gandía Barberá, A. (2015). Analysis of the feeding system in the injection process of peek in fixed partial dentures. Procedia Engineering. 132:1021-1028. doi:10.1016/j.proeng.2015.12.591S1021102813
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
- …