Productividad: proyecto de resolución aprobado por el Comité V el 12 de septiembre de 1955

Nowadays, many formal methods are used in the area of software development accompanied by a number of advanced theories and tools. However, more experiments are still required in order to provide significant evidence that will convince and encourage users to use, and gain more benefits from, those theories and tools. Event-B is a formalism used for specifying and reasoning about systems. Rodin is an open and extensible tool for Event-B specification, refinement and proof. The flash file system is a complex system. Such systems are a challenge to specify and verify at this moment in time. This system was chosen as a case study for our experiments, carried out using Event-B and the Rodin tool. The experiments were aimed at developing a rigorous model of flash-based file system; including implementation of the model, providing useful evidence and guidelines to developers and the software industry. We believe that these would convince users and make formal methods more accessible. An incremental refinement was chosen as a strategy in our development. The refinement was used for two different purposes: feature augmentation and structural refinement (covering event and machine decomposition). Several techniques and styles of modelling were investigated and compared; to produce some useful guidelines for modelling, refinement and proof. The model of the flash-based file system we have completed covers three main issues: fault-tolerance, concurrency and wear-levelling process. Our model can deal with concurrent read/write operations and other processes such as block relocation and block erasure. The model tolerates faults that may occur during reading/writing of files. We believe our development acts as an exemplar that other developers can learn from. We also provide systematic rules for translation of Event-B models into Java code. However, more work is required to make these rules more applicable and useful in the future

Systematic Construction of Critical Embedded Systems Using Event-B

International audienceWe propose a method to build critical embedded control systems in a systematic way. The method covers the modelling of both the digital part and the physical environment of a considered system, and their refinement until more concrete levels. It is based on Event-B in order to benefit from its materials, step-wise refinements and tools. Two main processes are distinguished: one to capture the global model, the other to detail the global model; they are made of several refinement steps which are accompanied with guidelines. The precise description of the interface between the digital and physical parts is used to start the modelling process. The recurrent categories of variables and events in control systems are described and used as guidelines to conduct a systematic construction. We illustrate the method with the landing gear system case study

A Formal Model of a Virtual Filesystem Switch

This work presents a formal model that is part of our effort to construct a verified file system for Flash memory. To modularize the verification we factor out generic aspects into a common component that is inspired by the Linux Virtual Filesystem Switch (VFS) and provides POSIX compatible operations. It relies on an abstract specification of its internal interface to concrete file system implementations (AFS). We proved that preconditions of AFS are respected and that the state is kept consistent. The model can be made executable and mounted into the Linux directory tree using FUSE

Detection of Babesia caballi (Nuttall, 1901) and Babesia equi (Laveran, 1901) in horses by microscopic examination in military farm in Gemlik

This study was caried out in military farm in Gemlik. A total of 133 horses were examined microscopically between March and September 1995. Peripher blood smears were prepared from the tail of the each horse. At the same time ticks were collected from the horses and the field. The blood smears were stained with 5% Giemsa solution and they were examined under microscope with ail objective. Babesia caballi and B. equi were detected in 16 (12%) and 8 (6%) out of the 133 horses examined respectively. B. caballi and B. equi were also found in 6 (4.5%) of the horses. None of the infected animals showed clinical reactions of babesiosis. The ticks were identified as Hyalomma marginatum and Rhipicephalus turanicus