Mapping RT-LOTOS specifications into Time Petri Nets

RT-LOTOS is a timed process algebra which enables compact and abstract specification of real-time systems. This paper proposes and illustrates a structural translation of RT-LOTOS terms into behaviorally equivalent (timed bisimilar) finite Time Petri nets. It is therefore possible to apply Time Petri nets verification techniques to the profit of RT-LOTOS. Our approach has been implemented in RTL2TPN, a prototype tool which takes as input an RT-LOTOS specification and outputs a TPN. The latter is verified using TINA, a TPN analyzer developed by LAAS-CNRS. The toolkit made of RTL2TPN and TINA has been positively benchmarked against previously developed RT-LOTOS verification tool

Synthesis and verification of constraints in the PGM protocol

Specifications of protocols usually involve several parameters, for example the number of retransmissions or the timeout delays. The properties satisfied by the protocol depend often on the relation between these parameters. Automatic synthesis of such relations becomes a difficult problem when the constraints are too complex, e.g., non-linear expressions between integer and/or real parameters. This paper reports about modeling and constraint synthesis in the Pragmatic General Multicast (PGM) protocol. The property that we aim to satisfy is the full reliability property for data transmission. The complexity of the PGM prevents us from doing automatic synthesis of this constraint. Instead, we propose a methodology to deal with this problem using classical model-checking tools for timed and finite systems. Our methodology consists of several steps. First, we identify the sources of complexity and, for each source, we propose several abstractions preserving the full reliability property. Then, we build an abstract parameterized model on which we test, after instantiation of parameters, that the basic properties of the protocol (deadlock freedom, liveness) are preserved. By analyzing the scenario which invalidate the full reliability property, we find a non-linear constraint between the parameters of the protocol. We check the relation found by instantiating the parameters with relevant values and applying model-checking

Impact on credit freeze before gate closing in CBS and GCL integration into TSN

International audienceThe Time Sensitive Networking (TSN) task group has added a set of mechanisms to Ethernet in order to provide a real-time network. In particular, the output port scheduling based on a Credit-Based Shaper (CBS) algorithm, that was introduced formerly by the Audio-Video Bridging (AVB) task group, has been enhanced with a time driven Gate Control List (GCL). This implies some update in the credit evolution rules, and several solutions may exist. In this paper, we compare the solution used in the standard with another one used in most papers, and also with a third one, designed as a trade-off between the two others. The comparison is first done on some hand-made examples, showing some credit overflow and unfairness potential problems. Then, simulations are done on a single switch with 3 CBS queues

On the compared expressiveness of arc, place and transition time Petri nets

International audienceIn this paper, we consider safe Time Petri Nets where time intervals (strict and large) are associated with places (TPPN), arcs (TAPN) or transitions (TTPN). We give the formal strong and weak semantics of these models in terms of Timed Transition Systems. We compare the expressiveness of the six models w.r.t. (weak) timed bisimilarity (behavioral semantics). The main results of the paper are : (i) with strong semantics, TAPN is strictly more expressive than TPPN and TTPN ; (ii) with strong semantics TPPN and TTPN are incomparable ; (iii) TTPN with strong semantics and TTPN with weak semantics are incomparable. Moreover, we give a complete classification by a set of 9 relations explained in a figure

Friction and inertia for a mirror in a thermal field

The force experienced by a mirror moving in vacuum vanishes in the case of uniform velocity or uniform acceleration, as a consequence of spatial symmetries of vacuum. These symmetries do not subsist in a thermal field. We give a general expression of the corresponding viscosity coefficient valid at any temperature and for any reflectivity function. We show that the computed motional force also contains a non vanishing inertial term. The associated mass correction goes to zero in the limiting cases of perfect reflection or of zero temperature.Comment: 5 page

Proof-by-Instance for Embedded Network Design: From Prototype to Tool Roadmap

International audienceProof-by-instance is a technique that ensures the correctness of the results of a computation rather than proving correct the tool carrying out the computation. We report here on the application of this idea to check the computations relevant for analyzing time bounds for AFDX networks. We have demonstrated the feasibility of the approach by applying a proof-of-concept implementation to an AFDX network of realistic size, and we outline the roadmap towards a mature industrial toolset. This approach should lead to a reduction of the time and cost of developing analysis tools used in the design of embedded networks where certification is mandatory

A Real-time Calculus Approach for Integrating Sporadic Events in Time-triggered Systems

In time-triggered systems, where the schedule table is predefined and statically configured at design time, sporadic event-triggered (ET) tasks can only be handled within specially dedicated slots or when time-triggered (TT) tasks finish their execution early. We introduce a new paradigm for synthesizing TT schedules that guarantee the correct temporal behavior of TT tasks and the schedulability of sporadic ET tasks with arbitrary deadlines. The approach first expresses a constraint for the TT task schedule in the form of a maximal affine envelope that guarantees that as long as the schedule generation respects this envelope, all sporadic ET tasks meet their deadline. The second step consists of modeling this envelope as a burst limiting constraint and building the TT schedule via simulating a modified Least-Laxity-First (LLF) scheduler. Using this novel technique, we show that we achieve equal or better schedulability and a faster schedule generation for most use-cases compared to other approaches inspired by, e.g., hierarchical scheduling. Moreover, we present an extension to our method that finds the most favourable schedule for TT tasks with respect to ET schedulability, thus increasing the probability of the computed TT schedule remaining feasible when ET tasks are later added or changed

Crystallization kinetics of polypropylenes. Effect of nucleating agents?

International audienceThermal conditions and formulation affect the crystallization mechanisms of polymers and the associated kinetics in a coupled manner. In that field, the objective of this investigation is to compare overall crystallization kinetics and structural organization of one clarified polypropylene (specifically designed for stretch-blow molding) and a homopolypropylene. Liquid/solid transitions are investigated in- and ex-situ under isothermal and non-isothermal conditions combining crossed-polarized optical microscopy, differential scanning calorimetry and X-ray diffraction. Clarified polypropylene has a very 'singular behavior' compared to homopolymer since no spherulites can be observed. However, it exhibits a semi-crystalline structure. The major α-phase coexists with some γ-phase even under quiescent conditions. Overall crystallization kinetics is rapid suggesting the existence of very efficient nucleating agent(s) and resulting in an increase of crystallization temperature. In parallel, the melting temperature of copolymer decreases by 20 °C compared to homopolymer, suggesting a drastic change in lamellae thickness. It is concluded that this unusual structure results from nucleation, which enforces high temperature crystallization, and copolymerization, which constraints the crystalline organization