1,726 research outputs found
Revisiting LFSMs
Linear Finite State Machines (LFSMs) are particular primitives widely used in
information theory, coding theory and cryptography. Among those linear
automata, a particular case of study is Linear Feedback Shift Registers (LFSRs)
used in many cryptographic applications such as design of stream ciphers or
pseudo-random generation. LFSRs could be seen as particular LFSMs without
inputs.
In this paper, we first recall the description of LFSMs using traditional
matrices representation. Then, we introduce a new matrices representation with
polynomial fractional coefficients. This new representation leads to sparse
representations and implementations. As direct applications, we focus our work
on the Windmill LFSRs case, used for example in the E0 stream cipher and on
other general applications that use this new representation.
In a second part, a new design criterion called diffusion delay for LFSRs is
introduced and well compared with existing related notions. This criterion
represents the diffusion capacity of an LFSR. Thus, using the matrices
representation, we present a new algorithm to randomly pick LFSRs with good
properties (including the new one) and sparse descriptions dedicated to
hardware and software designs. We present some examples of LFSRs generated
using our algorithm to show the relevance of our approach.Comment: Submitted to IEEE-I
A Visual Language for Web Querying and Reasoning
As XML is increasingly being used to represent information on the Web, query and reasoning languages for such data are needed. This article argues that in contrast to the navigational approach taken in particular by XPath and XQuery, a positional approach as used in the language Xcerpt is better suited for a straightforward visual representation. The constructs of the pattern- and rule-based query language Xcerpt are introduced and it is shown how the visual representation visXcerpt renders these constructs to form a visual query language for XML
Completing Queries: Rewriting of IncompleteWeb Queries under Schema Constraints
Reactive Web systems, Web services, and Web-based publish/
subscribe systems communicate events as XML messages, and in
many cases require composite event detection: it is not sufficient to react
to single event messages, but events have to be considered in relation to
other events that are received over time.
Emphasizing language design and formal semantics, we describe the
rule-based query language XChangeEQ for detecting composite events.
XChangeEQ is designed to completely cover and integrate the four complementary
querying dimensions: event data, event composition, temporal
relationships, and event accumulation. Semantics are provided as
model and fixpoint theories; while this is an established approach for rule
languages, it has not been applied for event queries before
Identification of Design Principles
This report identifies those design principles for a (possibly new) query and transformation
language for the Web supporting inference that are considered essential. Based upon these
design principles an initial strawman is selected. Scenarios for querying the Semantic Web
illustrate the design principles and their reflection in the initial strawman, i.e., a first draft of
the query language to be designed and implemented by the REWERSE working group I4
A Generic Module System forWeb Rule Languages: Divide and Rule
An essential feature in practically usable programming languages is
the ability to encapsulate functionality in reusable modules. Modules make large
scale projects tractable by humans. For Web and Semantic Web programming,
many rule-based languages, e.g. XSLT, CSS, Xcerpt, SWRL, SPARQL, and RIF
Core, have evolved or are currently evolving. Rules are easy to comprehend
and specify, even for non-technical users, e.g. business managers, hence easing
the contributions to the Web. Unfortunately, those contributions are arguably
doomed to exist in isolation as most rule languages are conceived without modularity,
hence without an easy mechanism for integration and reuse. In this paper
a generic module system applicable to many rule languages is presented. We
demonstrate and apply our generic module system to a Datalog-like rule language,
close in spirit to RIF Core. The language is gently introduced along the
EU-Rent use case. Using the Reuseware Composition Framework, the module
system for a concrete language can be achieved almost for free, if it adheres to
the formal notions introduced in this paper
Effective and Efficient Data Access in the Versatile Web Query Language Xcerpt
Access to Web data has become an integral part of many applications
and services. In the past, such data has usually been accessed
through human-tailoredHTMLinterfaces.Nowadays, rich client interfaces
in desktop applications or, increasingly, in browser-based clients ease data
access and allow more complex client processing based on XML or RDF
data retrieved throughWeb service interfaces. Convenient specifications of
the data processing on the client and flexible, expressive service interfaces
for data access become essential in this context.Web query languages such
as XQuery, XSLT, SPARQL, or Xcerpt have been tailored specifically for
such a setting: declarative and efficient access and processing ofWeb data.
Xcerpt stands apart among these languages by its versatility, i.e., its ability
to access not just oneWeb format but many. In this demonstration, two aspects
of Xcerpt are illustrated in detail: The first part of the demonstration
focuses on Xcerpt’s pattern matching constructs and rules to enable effective
and versatile data access. It uses a concrete practical use case from
bibliography management to illustrate these language features. Xcerpt’s
visual companion language visXcerpt is used to provide an intuitive interface
to both data and queries. The second part of the demonstration shows
recent advancements in Xcerpt’s implementation focusing on experimental
evaluation of recent complexity results and optimization techniques, as
well as scalability over a number of usage scenarios and input sizes
Modular Web Queries — From Rules to Stores
Even with all the progress in Semantic technology, accessing Web
data remains a challenging issue with new Web query languages and approaches
appearing regularly. Yet most of these languages, including W3C approaches
such as XQuery and SPARQL, do little to cope with the explosion of the data
size and schemata diversity and richness on the Web. In this paper we propose
a straightforward step toward the improvement of this situation that is simple to
realize and yet effective: Advanced module systems that make partitioning of (a)
the evaluation and (b) the conceptual design of complex Web queries possible.
They provide the query programmer with a powerful, but easy to use high-level
abstraction for packaging, encapsulating, and reusing conceptually related parts
(in our case, rules) of a Web query. The proposed module system combines ease
of use thanks to a simple core concept, the partitioning of rules and their consequences
in flexible “stores”, with ease of deployment thanks to a reduction
semantics. We focus on extending the rule-based Semantic Web query language
Xcerpt with such a module system though the same approach can be applied to
other (rule-based) languages as well
Trajectoire(s) de l’hydrosystème Saône-Rhône au paléoanthropocène
Notre PCR a pour objectif de documenter le paléoanthropocène rhodanien (depuis le Néolithique), de proposer des scenarii socio-environnementaux rétrospectifs, d’associer des connaissances sur les temporalités et processus du paléoanthropocène fluvial rhodanien, en insistant sur les principales bifurcations historiques de sa trajectoire (jusqu’au court-circuitage anthropogénique se son cours au xxe s.). Il aborde trois principales questions sur un continuum nord-sud de plus de 600 km, le co..
Milieux et peuplements en Bas-Dauphiné
Date de l'opération : 2007 (PC) L’étude des sources historiques et cartographiques depuis la fin du Moyen Âge La période comprise entre la fin du Moyen Âge et le XIXe s. a fait l’objet de nouvelles recherches en 2007 qui documentent l’occupation et la gestion du sol et la démographie historique des quatre ou cinq derniers siècles, une période qui a vu un développement sociétal considérable dans les milieux palustres et alluviaux des Basses Terres dauphinoises, lors d’un épisode de péjoration ..
Comment élaborer un environnement interactif adapté à la formation par le projet ? Étude d'un processus de conception
International audienceAujourd'hui, la formation ouverte et à distance (FOAD), dans l'enseignement supérieur en France, a dépassé le stade des projets et des expérimentations pilotes. On parle de campus numérique, de plate-forme de formation à distance, de LCMS, de générateur de documents hypermédias, etc. En ce sens, les ingénieries et recherches, dans le domaine, semblent s'attacher prioritairement à des questions de médiatisation de contenus, de production standardisée, d'indexation normée par des méta-données en vue de leur ré-exploitation et/ou mutualisation. Comme si les problématiques de contenus étaient premières au regard de celles des relations de formation. D'autres travaux, comme ceux sur l'apprentissage coopératif et le travail collaboratif (Bourguin et al., 2002), mettent cependant l'accent sur l'instrumentation des relations et interactions sociales et cognitives des acteurs de la formation. C'est dans une perspective proche, bien qu'un peu différente, que s'inscrivent nos travaux, qui cherchent à articuler pratiques de travail et de recherche, par la modélisation d'instruments et de dispositifs, développés à partir de situations concrètes de travail. Notre démarche a consisté, en premier lieu, à conduire un processus d'ingénierie en réponse à une commande d'instrumentation d'un dispositif de formation existant. L'analyse de cette demande, la prise en compte de son contexte et le processus de conception lui-même ont permis de travailler sur une triple problématique : pédagogique, économique, technologique. Ce processus d'ingénierie a débouché sur la construction d'un dispositif, intitulé Appui et la mise au point d'une plate-forme, visant à prendre en compte cette problématique. Les usages du dispositif et leur réinterrogation nous ont permis, en second lieu, d'envisager, de façon plus générale, une modélisation de l'accompagnement de projet à distance à partir du système de représentation des actions et interactions, intégré dans le dispositif. En conclusion de l'article, nous situerons les limites du modèle élaboré, en questionnant les conditions de sa reproductibilité
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