68,100 research outputs found
A Refinement Calculus for Logic Programs
Existing refinement calculi provide frameworks for the stepwise development
of imperative programs from specifications. This paper presents a refinement
calculus for deriving logic programs. The calculus contains a wide-spectrum
logic programming language, including executable constructs such as sequential
conjunction, disjunction, and existential quantification, as well as
specification constructs such as general predicates, assumptions and universal
quantification. A declarative semantics is defined for this wide-spectrum
language based on executions. Executions are partial functions from states to
states, where a state is represented as a set of bindings. The semantics is
used to define the meaning of programs and specifications, including parameters
and recursion. To complete the calculus, a notion of correctness-preserving
refinement over programs in the wide-spectrum language is defined and
refinement laws for developing programs are introduced. The refinement calculus
is illustrated using example derivations and prototype tool support is
discussed.Comment: 36 pages, 3 figures. To be published in Theory and Practice of Logic
Programming (TPLP
HF spectrum occupancy and antennas
This paper deals with the research made during the COST 296 action in the WG2, WP 2.3 in the antennas and HF spectrum management fields, focusing the Mitigation of Ionospheric Effects on Radio Systems as the subject of this COST action.info:eu-repo/semantics/publishedVersio
On the Unification of Process Semantics: Logical Semantics
We continue with the task of obtaining a unifying view of process semantics
by considering in this case the logical characterization of the semantics. We
start by considering the classic linear time-branching time spectrum developed
by R.J. van Glabbeek. He provided a logical characterization of most of the
semantics in his spectrum but, without following a unique pattern. In this
paper, we present a uniform logical characterization of all the semantics in
the enlarged spectrum. The common structure of the formulas that constitute all
the corresponding logics gives us a much clearer picture of the spectrum,
clarifying the relations between the different semantics, and allows us to
develop generic proofs of some general properties of the semantics.Comment: In Proceedings SOS 2011, arXiv:1108.279
Coherent supercontinuum generation in a silicon photonic wire in the telecommunication wavelength range
We demonstrate a fully coherent supercontinuum spectrum spanning 500 nm from a silicon-on-insulator photonic wire waveguide pumped at 1575 nm wavelength. An excellent agreement with numerical simulations is reported. The simulations also show that a high level of two-photon absorption can essentially enforce the coherence of the spectral broadening process irrespective of the pump pulse duration.SCOPUS: ar.jinfo:eu-repo/semantics/publishe
A wide-spectrum language for verification of programs on weak memory models
Modern processors deploy a variety of weak memory models, which for
efficiency reasons may (appear to) execute instructions in an order different
to that specified by the program text. The consequences of instruction
reordering can be complex and subtle, and can impact on ensuring correctness.
Previous work on the semantics of weak memory models has focussed on the
behaviour of assembler-level programs. In this paper we utilise that work to
extract some general principles underlying instruction reordering, and apply
those principles to a wide-spectrum language encompassing abstract data types
as well as low-level assembler code. The goal is to support reasoning about
implementations of data structures for modern processors with respect to an
abstract specification.
Specifically, we define an operational semantics, from which we derive some
properties of program refinement, and encode the semantics in the rewriting
engine Maude as a model-checking tool. The tool is used to validate the
semantics against the behaviour of a set of litmus tests (small assembler
programs) run on hardware, and also to model check implementations of data
structures from the literature against their abstract specifications
Unwinding of a one-dimensional topological superconductor
We show that a topological superconductor made of four chains of
superconducting spinless fermions characterized by four Majorana edge states
can adiabatically be deformed into a trivial band insulator. To unwind this
time-reversal invariant topological superconductor, interactions to spinful
fermions are switched on along an adiabatic path. Thereby, we couple modes
which belong to two different representations of the time-reversal symmetry
operator T with T^2 = 1 and T^2 = -1, respectively. This observation can be
understood by investigating how the relevant symmetries act on the entanglement
spectrum giving rise to four instead of eight different topological phases with
Majorana edge modes. We also show that a simple level crossing of doubly and
singly degenerate states occurs in the entanglement spectrum upon deforming the
quantum state.Comment: 7 pages, substantial changes in the semantics compared to first
versio
- …