50 research outputs found
FORMAL SPECIFICATIONS AND COMMAND MODELING IN SOFTWARE SYSTEMS WITH A COMPLEX COMMAND STRUCTURE
Get PDFCommands are an important part of large scale industrial software specifications, especially where the specification is separated from its implementation as in open software standards. Commands can be complex because of large numbers of parameters, dependencies among parameters, subtle side effects, and lack of abstraction. We present a formal approach for command modeling and apply it to IBM\u27s Distributed Data Management Architecture (DDM), a complex, large scale specification of data access on remote and heterogeneous IBM systems. Our approach consists of three parts: a declarative, executable command specification language, an incremental specification technique, and automated reasoning tools. The command specification language provides a formal interpretation of the structural (input-output) and behavioral properties (state constraints/change) of commands. To manage the details of complex commands with numerous inter-dependent arguments, a novel incremental specification technique and several tools for incremental definition and browsing are presented. Two forms of automated reasoning are also demonstrated: type checking to ensure well-typed expressions and target system tracing to simulate command execution. Lessons learned from our experience with the DDM are also discussed
Isotope evidence for the use of marine resources in the Eastern Iberian Mesolithic
Get PDFThere are relatively few coastal Mesolithic sites in the Iberian Mediterranean region, probably due to a number of factors including sea level changes and the disappearance of sites due to agriculture and urbanisation. However, recent excavations have uncovered inland sites that have marine faunal remains (i.e. molluscs and fish) and lithics from the coastal area, which both indicate interactions between the coast and the upland valleys. These inland sites are located at a distance of 30e50 km from todayÂżs coastline and are at altitudes higher than 1000 m. We report on additional information on the links between the coast and these inland sites through the use of dietary isotope analysis (carbon and nitrogen stable isotope analysis) of collagen extracted from human and faunal remains at the sites of Coves de Santa Maira, Penya del Comptador and Cingle del Mas Nou. The results indicate that Mesolithic diet in this region was largely based on C3 terrestrial resources, but there was measurable evidence of low-level consumption of marine resources at both coastal and inland sites
Ten millennia of hepatitis B virus evolution
Get PDFHepatitis B virus (HBV) has been infecting humans for millennia and remains a global health problem, but its past diversity and dispersal routes are largely unknown. We generated HBV genomic data from 137 Eurasians and Native Americans dated between ~10,500 and ~400 years ago. We date the most recent common ancestor of all HBV lineages to between ~20,000 and 12,000 years ago, with the virus present in European and South American hunter-gatherers during the early Holocene. After the European Neolithic transition, Mesolithic HBV strains were replaced by a lineage likely disseminated by early farmers that prevailed throughout western Eurasia for ~4000 years, declining around the end of the 2nd millennium BCE. The only remnant of this prehistoric HBV diversity is the rare genotype G, which appears to have reemerged during the HIV pandemic
