Logic-based schedulability analysis for compositional hard real-time embedded systems

This is the author's version of the work. It is posted here by permission of ACM for your personal use. Not for redistribution. The definitive version was published in SIGBED Review, VOL.12, ISS.1, http://doi.acm.org/10.1145/2752801.2752808Over the past decades several approaches for schedu- lability analysis have been proposed for both uniprocessor and multi-processor real-time systems. Although different techniques are employed, very little has been put forward in using formal specifications, with the consequent possibility for misinterpretations or ambiguities in the problem statement. Using a logic based approach to schedulability analysis in the design of hard real-time systems eases the synthesis of correct-by- construction procedures for both static and dynamic verification processes. In this paper we propose a novel approach to schedulability analysis based on a timed temporal logic with time durations. Our approach subsumes classical methods for uniprocessor scheduling analysis over compositional resource models by providing the developer with counter-examples, and by ruling out schedules that cause unsafe violations on the system. We also provide an example showing the effectiveness of our proposal.This work was partially supported by National Funds through FCT (Portuguese Foundation for Science and Technology) and by ERDF (European Regional Development Fund) through COMPETE (Operational Programme ’Thematic Fac- tors of Competitiveness’), within projects Ref. FCOMP-01- 0124-FEDER-022701 (CISTER), FCOMP-01-0124-FEDER- 015006 (VIPCORE) and FCOMP-01-0124-FEDER-020486 (AVIACC)

A Reduction from Unbounded Linear Mixed Arithmetic Problems into Bounded Problems

We present a combination of the Mixed-Echelon-Hermite transformation and the Double-Bounded Reduction for systems of linear mixed arithmetic that preserve satisfiability and can be computed in polynomial time. Together, the two transformations turn any system of linear mixed constraints into a bounded system, i.e., a system for which termination can be achieved easily. Existing approaches for linear mixed arithmetic, e.g., branch-and-bound and cuts from proofs, only explore a finite search space after application of our two transformations. Instead of generating a priori bounds for the variables, e.g., as suggested by Papadimitriou, unbounded variables are eliminated through the two transformations. The transformations orient themselves on the structure of an input system instead of computing a priori (over-)approximations out of the available constants. Experiments provide further evidence to the efficiency of the transformations in practice. We also present a polynomial method for converting certificates of (un)satisfiability from the transformed to the original system

Satisfiability Checking and Symbolic Computation

Symbolic Computation and Satisfiability Checking are viewed as individual research areas, but they share common interests in the development, implementation and application of decision procedures for arithmetic theories. Despite these commonalities, the two communities are currently only weakly connected. We introduce a new project SC-square to build a joint community in this area, supported by a newly accepted EU (H2020-FETOPEN-CSA) project of the same name. We aim to strengthen the connection between these communities by creating common platforms, initiating interaction and exchange, identifying common challenges, and developing a common roadmap. This abstract and accompanying poster describes the motivation and aims for the project, and reports on the first activities.Comment: 3 page Extended Abstract to accompany an ISSAC 2016 poster. Poster available at http://www.sc-square.org/SC2-AnnouncementPoster.pd

Cognitive disorders in patients with chronic kidney disease: Approaches to prevention and treatment

Background: Cognitive impairment is common in patients with chronic kidney disease (CKD), and early intervention may prevent the progression of this condition. Methods: Here, we review interventions for the complications of CKD (anemia, secondary hyperparathyroidism, metabolic acidosis, harmful effects of dialysis, the accumulation of uremic toxins) and for prevention of vascular events, interventions that may potentially be protective against cognitive impairment. Furthermore, we discuss nonpharmacological and pharmacological methods to prevent cognitive impairment and/or minimize the latter's impact on CKD patients' daily lives. Results: A particular attention on kidney function assessment is suggested during work-up for cognitive impairment. Different approaches are promising to reduce cognitive burden in patients with CKD but the availabe dedicated data are scarce. Conclusions: There is a need for studies assessing the effect of interventions on the cognitive function of patients with CKD

Lupus nephritis: Is it necessary to systematically repeat kidney biopsy?

International audienc

Why3 — Where Programs Meet Provers

Abstract. We present Why3, a tool for deductive program verification, and WhyML, its programming and specification language. WhyML is a first-order language with polymorphic types, pattern matching, and inductive predicates. Programs can make use of record types with mutable fields, type invariants, and ghost code. Verification conditions are discharged by Why3 with the help of various existing automated and interactive theorem provers. To keep verification conditions tractable and comprehensible, WhyML imposes a static control of aliases that obviates the use of a memory model. A user can write WhyML programs directly and get correct-by-construction OCaml programs via an automated extraction mechanism. WhyML is also used as an intermediate language for the verification of C, Java, or Ada programs. We demonstrate the benefits of Why3 and WhyML on nontrivial examples of program verification.

[Rituximab-induced acute thrombocytopenia in a patient with chronic lymphocytic leukemia]

Rituximab is a chimeric anti-CD20 monoclonal antibody generally well tolerated. However, a severe but rare rituximab-related immune-toxic syndrome, associating fever, chills and thrombocytopenia can occur shortly after the infusion

Formal analysis of the compact position reporting algorithm

International audienceThe Automatic Dependent Surveillance-Broadcast (ADS-B) system allows aircraft to communicate current state information, including position and velocity messages, to other aircraft in their vicinity andto ground stations. The Compact Position Reporting (CPR) algorithm is the ADS-B protocol responsiblefor the encoding and decoding of aircraft positions. CPR is sensitive to computer arithmetic since it relieson functions that are intrinsically unstable such as floor and modulus. In this paper, a formal verificationof the CPR algorithm is presented. In contrast to previous work, the algorithm presented here encompassesthe entire range of message types supported by ADS-B. The paper also presents two implementations ofthe CPR algorithm, one in double-precision floating-point and one in 32-bit unsigned integers, which areboth formally verified against the real-number algorithm. The verification proceeds in three steps. For eachimplementation, a version of CPR, which is simplified and manipulated to reduce numerical instability andleverage features of the datatypes, is proposed. Then, the Prototype Verification System (PVS) is used toformally prove real conformance properties, which assert that the ideal real-number counterpart of the improved algorithm is mathematically equivalent to the standard CPR definition. Finally, the static analyzerFrama-C is used to verify software conformance properties, which say that the software implementation ofthe improved algorithm is correct with respect to its idealized real-number counterpart. In concert, the twoproperties guarantee that the implementation meets the original specification. The two implementations willbe included in the revised version of the ADS-B standards document as the reference implementation of theCPR algorithm