36 research outputs found
Exploring the link between test suite quality and automatic specification inference
While no one doubts the importance of correct and complete specifications, many industrial systems
still do not have formal specifications written out â and even when they do, it is hard to check their
correctness and completeness. This work explores the possibility of using an invariant extraction tool
such as Daikon to automatically infer specifications from available test suites with the idea of aiding
software engineers to improve the specifications by having another version to compare to. Given that
our initial experiments did not produce satisfactory results, in this paper we explore which test suite
attributes influence the quality of the inferred specification. Following further study, we found that
instruction, branch and method coverage are correlated to high recall values, reaching up to 97.93%.peer-reviewe
Control-flow residual analysis for symbolic automata
This research has received funding from the European Unionâs Horizon 2020 research and innovation programme under grant number 666363.Where full static analysis of systems fails to scale up due to system size, dynamic monitoring has been increasingly used to ensure system correctness. The downside is, however, runtime overheads which are induced by the additional monitoring code instrumented. To address this issue, various approaches have been proposed in the literature to use static analysis in order to reduce monitoring overhead. In this paper we generalise existing work which uses control-flow static analysis to optimise properties specified as automata, and prove how similar analysis can be applied to more expressive symbolic automata - enabling reduction of monitoring instrumentation in the system, and also monitoring logic. We also present empirical evidence of the effectiveness of this approach through an analysis of the effect of monitoring overheads in a financial transaction system.peer-reviewe
Preliminary results towards contract monitorability
This paper discusses preliminary investigations on the monitorability of contracts for web service descriptions. There are settings where servers do not guarantee statically whether they satisfy some specified contract, which forces the client (i.e., the entity interacting with the server) to perform dynamic checks. This scenario may be viewed as an instance of Runtime Verification, where a pertinent question is whether contracts can be monitored for adequately at runtime, otherwise stated as the monitorability of contracts. We consider a simple language of finitary contracts describing both clients and servers, and develop a formal framework that describes server contract monitoring. We define monitor properties that potentially contribute towards a comprehensive notion of contract monitorability and show that our simple contract language satisfies these properties.peer-reviewe
Reliability and fault-tolerance by choreographic design
Distributed programs are hard to get right because they are required to be open, scalable, long-running,
and tolerant to faults. In particular, the recent approaches to distributed software based on (micro-)services where different services are developed independently by disparate teams exacerbate the
problem. In fact, services are meant to be composed together and run in open context where unpredictable behaviours can emerge. This makes it necessary to adopt suitable strategies for monitoring
the execution and incorporate recovery and adaptation mechanisms so to make distributed programs
more flexible and robust. The typical approach that is currently adopted is to embed such mechanisms
in the program logic, which makes it hard to extract, compare and debug. We propose an approach
that employs formal abstractions for specifying failure recovery and adaptation strategies. Although
implementation agnostic, these abstractions would be amenable to algorithmic synthesis of code,
monitoring and tests. We consider message-passing programs (a la Erlang, Go, or MPI) that are
gaining momentum both in academia and industry. Our research agenda consists of (1) the definition
of formal behavioural models encompassing failures, (2) the specification of the relevant properties of
adaptation and recovery strategy, (3) the automatic generation of monitoring, recovery, and adaptation
logic in target languages of interest.peer-reviewe
Land Productivity and Economic Development: Caloric Suitability vs. Agricultural Suitability
The redmapper galaxy cluster catalog from DES Science Verification data
We describe updates to the redMaPPer algorithm, a photometric red-sequence cluster finder specifically designed for large photometric surveys. The updated algorithm is applied to 150 {{deg}}2 of Science Verification (SV) data from the Dark Energy Survey (DES), and to the Sloan Digital Sky Survey (SDSS) DR8 photometric data set. The DES SV catalog is locally volume limited and contains 786 clusters with richness lambda \gt 20 (roughly equivalent to {M}{{500c}}âł {10}14 {h}70-1 {M}o ) and 0.2\lt z\lt 0.9. The DR8 catalog consists of 26,311 clusters with 0.08\lt z\lt 0.6, with a sharply increasing richness threshold as a function of redshift for zâł 0.35. The photometric redshift performance of both catalogs is shown to be excellent, with photometric redshift uncertainties controlled at the {sigma }z/(1+z)~ 0.01 level for zâČ 0.7, rising to ~0.02 at z~ 0.9 in DES SV. We make use of Chandra and XMM X-ray and South Pole Telescope Sunyaev--Zeldovich data to show that the centering performance and mass--richness scatter are consistent with expectations based on prior runs of redMaPPer on SDSS data. We also show how the redMaPPer photo-z and richness estimates are relatively insensitive to imperfect star/galaxy separation and small-scale star masks
Multi-messenger Observations of a Binary Neutron Star Merger
On 2017 August 17 a binary neutron star coalescence candidate (later
designated GW170817) with merger time 12:41:04 UTC was observed through
gravitational waves by the Advanced LIGO and Advanced Virgo detectors.
The Fermi Gamma-ray Burst Monitor independently detected a gamma-ray
burst (GRB 170817A) with a time delay of ⌠1.7 {{s}} with respect to
the merger time. From the gravitational-wave signal, the source was
initially localized to a sky region of 31 deg2 at a
luminosity distance of {40}-8+8 Mpc and with
component masses consistent with neutron stars. The component masses
were later measured to be in the range 0.86 to 2.26 {M}ÈŻ
. An extensive observing campaign was launched across the
electromagnetic spectrum leading to the discovery of a bright optical
transient (SSS17a, now with the IAU identification of AT 2017gfo) in NGC
4993 (at ⌠40 {{Mpc}}) less than 11 hours after the merger by the
One-Meter, Two Hemisphere (1M2H) team using the 1 m Swope Telescope. The
optical transient was independently detected by multiple teams within an
hour. Subsequent observations targeted the object and its environment.
Early ultraviolet observations revealed a blue transient that faded
within 48 hours. Optical and infrared observations showed a redward
evolution over âŒ10 days. Following early non-detections, X-ray and
radio emission were discovered at the transientâs position ⌠9
and ⌠16 days, respectively, after the merger. Both the X-ray and
radio emission likely arise from a physical process that is distinct
from the one that generates the UV/optical/near-infrared emission. No
ultra-high-energy gamma-rays and no neutrino candidates consistent with
the source were found in follow-up searches. These observations support
the hypothesis that GW170817 was produced by the merger of two neutron
stars in NGC 4993 followed by a short gamma-ray burst (GRB 170817A) and
a kilonova/macronova powered by the radioactive decay of r-process
nuclei synthesized in the ejecta.</p