31,180 research outputs found
Automatic Verification of Transactions on an Object-Oriented Database
In the context of the object-oriented data model, a compiletime approach is given that provides for a significant reduction of the amount of run-time transaction overhead due to integrity constraint checking. The higher-order logic Isabelle theorem prover is used to automatically prove which constraints might, or might not be violated by a given transaction in a manner analogous to the one used by Sheard and Stemple (1989) for the relational data model. A prototype transaction verification tool has been implemented, which automates the semantic mappings and generates proof goals for Isabelle. Test results are discussed to illustrate the effectiveness of our approach
Transforming Normal Programs by Replacement
The replacement transformation operation, already defined in [28], is studied wrt normal programs. We give applicability conditions able to ensure the correctness of the operation wrt Fitting's and Kunen's semantics. We show how replacement can mimic other transformation operations such as thinning, fattening and folding, thus producing applicability conditions for them too. Furthermore we characterize a transformation sequence for which the preservation of Fitting's and Kunen's semantics is ensured
More on Unfold/Fold Transformations of Normal Programs: Preservation of Fitting's Semantics
The unfold/fold transformation system defined by Tamaki and Sato was meant for definite programs. It transforms a program into an equivalent one in the sense of both the least Herbrand model semantics and the Computed Answer Substitution semantics. Seki extended the method to normal programs and specialized it in order to preserve also the finite failure set. The resulting system is correct wrt nearly all the declarative semantics for normal programs. An exception is Fitting's model semantics. In this paper we consider a slight variation of Seki's method and we study its correctness wrt Fitting's semantics. We define an applicability condition for the fold operation and we show that it ensures the preservation of the considered semantics through the transformation
A scalable hardware and software control apparatus for experiments with hybrid quantum systems
Modern experiments with fundamental quantum systems - like ultracold atoms,
trapped ions, single photons - are managed by a control system formed by a
number of input/output electronic channels governed by a computer. In hybrid
quantum systems, where two or more quantum systems are combined and made to
interact, establishing an efficient control system is particularly challenging
due to the higher complexity, especially when each single quantum system is
characterized by a different timescale. Here we present a new control apparatus
specifically designed to efficiently manage hybrid quantum systems. The
apparatus is formed by a network of fast communicating Field Programmable Gate
Arrays (FPGAs), the action of which is administrated by a software. Both
hardware and software share the same tree-like structure, which ensures a full
scalability of the control apparatus. In the hardware, a master board acts on a
number of slave boards, each of which is equipped with an FPGA that locally
drives analog and digital input/output channels and radiofrequency (RF) outputs
up to 400 MHz. The software is designed to be a general platform for managing
both commercial and home-made instruments in a user-friendly and intuitive
Graphical User Interface (GUI). The architecture ensures that complex control
protocols can be carried out, such as performing of concurrent commands loops
by acting on different channels, the generation of multi-variable error
functions and the implementation of self-optimization procedures. Although
designed for managing experiments with hybrid quantum systems, in particular
with atom-ion mixtures, this control apparatus can in principle be used in any
experiment in atomic, molecular, and optical physics.Comment: 10 pages, 12 figure
On the practicality of global flow analysis of logic programs
This paper addresses the issue of the practicality of global flow analysis in logic program compilation, in terms of both speed and precision of analysis. It discusses design and implementation aspects of two practical abstract interpretation-based flow analysis systems: MA3, the MOO Andparallel Analyzer and Annotator; and Ms, an experimental mode inference system developed for SB-Prolog. The paper also provides performance data obtained from these implementations. Based on these results, it is concluded that the overhead of global flow analysis is not prohibitive, while the results of analysis can be quite precise and useful
- …