Inductive Verification of Data Model Invariants for Web Applications ∗

Modern software applications store their data in remote cloud servers. Users interact with these applications using web browsers or thin clients running on mobile devices. A key issue in dependability of these applications is the correctness of the actions that update the data store, which are triggered by user requests. In this paper, we present techniques for automatically checking if the actions of an application preserve the data model invariants. Our approach first automatically data store, from a given application using instrumented execution. The abstract data store identifies the sets of objects and relations (associations) used by the application, and the actions that update the data store by deleting or creating objects or by changing the relations among the objects. We show that checking invariants of an abstract data store corresponds to inductive invariant verification, and can be done using a mapping to First Order Logic (FOL) and using a FOL theorem prover. We implemented this approach for the Rails framework and applied it to three open source applications. We found four previously unknown bugs and reported them to the developers, who confirmed and immediately fixed two of them

Education, occupational class, and cognitive decline in preclinical dementia

We investigated education and occupational influences as markers of cognitive reserve in relation to cognitive performance and decline on multiple fluid and crystallized abilities in preclinical dementia. From the total sample of 702 participants stemming from the OCTO-Twin Study (Sweden), aged 80+ at baseline in 1992-1993, only those who developed dementia during the study period (N = 127) were included in these analyses. Random effects models were used to examine the level of performance at the time of dementia diagnosis and the rates of decline prior to diagnosis. The results demonstrated that both fluid and crystallized abilities decline in preclinical stages, and that education and occupational class have independent moderating roles on the cognitive performance at the time of diagnosis, but not on the rates of decline

An international evaluation of cognitive reserve and memory changes in early old age in ten European countries

BACKGROUND: Cognitive reserve was postulated to explain individual differences in susceptibility to ageing, offering apparent protection to those with higher education. We investigated the association between education and change in memory in early old age. METHODS: Immediate and delayed memory scores from over 10,000 individuals aged 65 years and older, from 10 countries of the Survey of Health, Ageing and Retirement in Europe (SHARE), were modeled as a function of time in the study over an 8-year period, fitting independent latent growth models (LGM). Education was used as a marker of cognitive reserve and evaluated in associations with memory performance and rate of change, while accounting for income, general health, smoking, body mass index (BMI), sex and baseline age. RESULTS: In most countries, more educated individuals performed better on both memory tests at baseline, compared to those less educated. However, education was not protective against faster decline, except for in Spain for both immediate and delayed recall (0.007 (SE=0.003) & 0.006 (SE=0.002), and Switzerland for immediate recall 0.006 (SE=0.003). Interestingly, highly educated Italian respondents had slightly faster declines in immediate recall (-0.006 (SE=0.003)). CONCLUSIONS: We found weak evidence of a protective effect of education on memory change in most European samples, although there was a positive association with memory performance at individuals' baseline assessment

Does education explain the terminal decline in the oldest-old? Evidence from two longitudinal studies of ageing

AbstractBackground Cognitive performance substantially deteriorates close to death, as postulated by the terminal decline hypothesis. However, the association between education and terminal decline remains controversial. This study investigated the role of education in terminal decline in two European longitudinal studies of oldest-old. Methods Participants were from the Newcastle 85+, UK (n=702), and Octogenarian Twins (OCTO-Twin), Sweden (n= 845). They were assessed biannually over three and five consecutive waves, respectively. In a coordinated analysis, multilevel models were used to examine the association between education and terminal decline on mini-mental state examination (MMSE), controlling for age at baseline, dementia incidence, sex, and time to death from the study entry within each cohort. Cognitive decline was modelled as a linear function of time to death in both cohorts and as a quadratic function in the OCTO-Twin study (because of longer follow-up). Education was a continuous measure (ranging from 6 to 20 years in Newcastle 85+ and 0 to 23 years in OCTO-Twin). Findings A typical British man, aged 85 at baseline, with 10 years’ education, entered the terminal phase at around 2·5 years before death, and the mean rate of decline was −1·04 MMSE points with each year closer to the time of death (SEM 0·25, p<0·0001). By contrast, a Swedish man, aged 83 years, with an average of 7 years’ education, entered the terminal phase at around 8 years from death, after which the rate of cognitive decline steepened by −1·70 points per year closer to the time of death (SEM 0·20, p<0·0001) and accelerated by −0·11 (SEM 0·01, p<0·0001). Education was positively associated with the estimated mean MMSE scores before death only in OCTO-Twin (0·43, SEM 0·15; p=0·003) and did not attenuate the rate of terminal decline in either cohort. Interpretation Decline and acceleration of this decline were detectable in both studies before death, with steeper rates of decline observed in the Swedish cohort. However, this process was not lessened by education itself. This work contributes to a better understanding of the transition from the subtle cognitive changes associated with age to those of neurological substance, and the role of education in this decline. Funding The funding sources of this work were the Alzheimer's Society (grant number 144) and the Medical Research Council (unit programme number MC_UU_12019/1)

Checking Interaction-Based Declassification Policies for Android Using Symbolic Execution

Mobile apps can access a wide variety of secure information, such as contacts and location. However, current mobile platforms include only coarse access control mechanisms to protect such data. In this paper, we introduce interaction-based declassification policies, in which the user's interactions with the app constrain the release of sensitive information. Our policies are defined extensionally, so as to be independent of the app's implementation, based on sequences of security-relevant events that occur in app runs. Policies use LTL formulae to precisely specify which secret inputs, read at which times, may be released. We formalize a semantic security condition, interaction-based noninterference, to define our policies precisely. Finally, we describe a prototype tool that uses symbolic execution to check interaction-based declassification policies for Android, and we show that it enforces policies correctly on a set of apps.Comment: This research was supported in part by NSF grants CNS-1064997 and 1421373, AFOSR grants FA9550-12-1-0334 and FA9550-14-1-0334, a partnership between UMIACS and the Laboratory for Telecommunication Sciences, and the National Security Agenc

Symbolic Partial-Order Execution for Testing Multi-Threaded Programs

We describe a technique for systematic testing of multi-threaded programs. We combine Quasi-Optimal Partial-Order Reduction, a state-of-the-art technique that tackles path explosion due to interleaving non-determinism, with symbolic execution to handle data non-determinism. Our technique iteratively and exhaustively finds all executions of the program. It represents program executions using partial orders and finds the next execution using an underlying unfolding semantics. We avoid the exploration of redundant program traces using cutoff events. We implemented our technique as an extension of KLEE and evaluated it on a set of large multi-threaded C programs. Our experiments found several previously undiscovered bugs and undefined behaviors in memcached and GNU sort, showing that the new method is capable of finding bugs in industrial-size benchmarks.Comment: Extended version of a paper presented at CAV'2

Network-wide Configuration Synthesis

Computer networks are hard to manage. Given a set of high-level requirements (e.g., reachability, security), operators have to manually figure out the individual configuration of potentially hundreds of devices running complex distributed protocols so that they, collectively, compute a compatible forwarding state. Not surprisingly, operators often make mistakes which lead to downtimes. To address this problem, we present a novel synthesis approach that automatically computes correct network configurations that comply with the operator's requirements. We capture the behavior of existing routers along with the distributed protocols they run in stratified Datalog. Our key insight is to reduce the problem of finding correct input configurations to the task of synthesizing inputs for a stratified Datalog program. To solve this synthesis task, we introduce a new algorithm that synthesizes inputs for stratified Datalog programs. This algorithm is applicable beyond the domain of networks. We leverage our synthesis algorithm to construct the first network-wide configuration synthesis system, called SyNET, that support multiple interacting routing protocols (OSPF and BGP) and static routes. We show that our system is practical and can infer correct input configurations, in a reasonable amount time, for networks of realistic size (> 50 routers) that forward packets for multiple traffic classes.Comment: 24 Pages, short version published in CAV 201

Investigating pediatric disorders with induced pluripotent stem cells

The study of disease pathophysiology has long relied on model systems, including animal models and cultured cells. In 2006, Shinya Yamanaka achieved a breakthrough by reprogramming somatic cells into induced pluripotent stem cells (iPSCs). This revolutionary discovery provided new opportunities for disease modeling and therapeutic intervention. With established protocols, investigators can generate iPSC lines from patient blood, urine, and tissue samples. These iPSCs retain ability to differentiate into every human cell type. Advances in differentiation and organogenesis move cellular in vitro modeling to a multicellular model capable of recapitulating physiology and disease. Here, we discuss limitations of traditional animal and tissue culture models, as well as the application of iPSC models. We highlight various techniques, including reprogramming strategies, directed differentiation, tissue engineering, organoid developments, and genome editing. We extensively summarize current established iPSC disease models that utilize these techniques. Confluence of these technologies will advance our understanding of pediatric diseases and help usher in new personalized therapies for patients

Co-circulation of a novel phlebovirus and Massilia virus in sandflies, Portugal

Free PMC Article: www.ncbi.nlm.nih.gov/pmc/articles/pmid/26497645/Background: In Portugal, entomological surveys to detect phleboviruses in their natural vectors have not been performed so far. Thus, the aims of the present study were to detect, isolate and characterize phleboviruses in sandfly populations of Portugal. Findings: From May to October 2007–2008, 896 female sandflies were trapped in Arrábida region, located on the southwest coast of Portugal. Phlebovirus RNA was detected by using a pan-phlebovirus RT-PCR in 4 out of 34 Phlebotomus perniciosus pools. Direct sequencing of the amplicons showed that 2 samples exhibited 72 % nucleotide identity with Arbia virus, and two showed 96 % nucleotide identity with Massilia virus. The Arbia-like virus (named Alcube virus) was isolated in cell culture and complete genomic sequences of one Alcube and two Massila viruses were determined using next-generation sequencing technology. Phylogenetic analysis demonstrated that Alcube virus clustered with members of the Salehabad virus species complex. Within this clade, Alcube virus forms a monophyletic lineage with the Arbia, Salehabad and Adana viruses sharing a common ancestor. Arbia virus has been identified as the most closely related virus with 20-28 % nucleotide and 10-27 % amino acid divergences depending on the analysed segment. Conclusions: We have provided genetic evidence for the circulation of a novel phlebovirus species named Alcube virus in Ph. perniciosus and co-circulation of Massilia virus, in Arrábida region, southwest of Portugal. Further epidemiological investigations and surveillance for sandfly-borne phleboviruses in Portugal are needed to elucidate their medical importance.This work was partially funded by the FCT project “New arboviruses isolated in Portugal. Risk assessment and public health application" (PTDC/SAU-SAP/119199/2010)