64,028 research outputs found
PROSET — A Language for Prototyping with Sets
We discuss the prototyping language PROSET(Prototyping with Sets) as a language for experimental and evolutionary prototyping, focusing its attention on algorithm design. Some of PROSET’s features include generative communication, flexible exception handling and the integration of persistence. A discussion of some issues pertaining to the compiler and the programming environment conclude the pape
Next generation software environments : principles, problems, and research directions
The past decade has seen a burgeoning of research and development in software environments. Conferences have been devoted to the topic of practical environments, journal papers produced, and commercial systems sold. Given all the activity, one might expect a great deal of consensus on issues, approaches, and techniques. This is not the case, however. Indeed, the term "environment" is still used in a variety of conflicting ways. Nevertheless substantial progress has been made and we are at least nearing consensus on many critical issues.The purpose of this paper is to characterize environments, describe several important principles that have emerged in the last decade or so, note current open problems, and describe some approaches to these problems, with particular emphasis on the activities of one large-scale research program, the Arcadia project. Consideration is also given to two related topics: empirical evaluation and technology transition. That is, how can environments and their constituents be evaluated, and how can new developments be moved effectively into the production sector
Answer Sets for Consistent Query Answering in Inconsistent Databases
A relational database is inconsistent if it does not satisfy a given set of
integrity constraints. Nevertheless, it is likely that most of the data in it
is consistent with the constraints. In this paper we apply logic programming
based on answer sets to the problem of retrieving consistent information from a
possibly inconsistent database. Since consistent information persists from the
original database to every of its minimal repairs, the approach is based on a
specification of database repairs using disjunctive logic programs with
exceptions, whose answer set semantics can be represented and computed by
systems that implement stable model semantics. These programs allow us to
declare persistence by defaults and repairing changes by exceptions. We
concentrate mainly on logic programs for binary integrity constraints, among
which we find most of the integrity constraints found in practice.Comment: 34 page
A generic persistence model for CLP systems (and two useful implementations)
This paper describes a model of persistence in (C)LP languages and two different and practically very useful ways to implement this model in current systems. The fundamental idea is that persistence is a characteristic of certain dynamic predicates (Le., those which encapsulate
state). The main effect of declaring a predicate persistent is that the dynamic changes made to such predicates persist from one execution to the next one. After proposing a syntax for declaring persistent predicates, a simple, file-based implementation of the concept is presented and
some examples shown. An additional implementation is presented which stores persistent predicates in an external datábase. The abstraction of the concept of persistence from its implementation allows developing applications
which can store their persistent predicates alternatively in files or databases with only a few simple changes to a declaration stating the location and modality used for persistent storage. The paper presents the model, the implementation approach in both the cases of using files
and relational databases, a number of optimizations of the process (using information obtained from static global analysis and goal clustering), and performance results from an implementation of these ideas
Process-Oriented Parallel Programming with an Application to Data-Intensive Computing
We introduce process-oriented programming as a natural extension of
object-oriented programming for parallel computing. It is based on the
observation that every class of an object-oriented language can be instantiated
as a process, accessible via a remote pointer. The introduction of process
pointers requires no syntax extension, identifies processes with programming
objects, and enables processes to exchange information simply by executing
remote methods. Process-oriented programming is a high-level language
alternative to multithreading, MPI and many other languages, environments and
tools currently used for parallel computations. It implements natural
object-based parallelism using only minimal syntax extension of existing
languages, such as C++ and Python, and has therefore the potential to lead to
widespread adoption of parallel programming. We implemented a prototype system
for running processes using C++ with MPI and used it to compute a large
three-dimensional Fourier transform on a computer cluster built of commodity
hardware components. Three-dimensional Fourier transform is a prototype of a
data-intensive application with a complex data-access pattern. The
process-oriented code is only a few hundred lines long, and attains very high
data throughput by achieving massive parallelism and maximizing hardware
utilization.Comment: 20 pages, 1 figur
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