26,955 research outputs found
A common framework for classifying and specifying deductive database updating problems
Several problems may arise when updating a deductive database. Up to now,
the general approach of the research related to deductive database updating problems
has been to provide specific methods for solving particular problems. However, ali
these methods are explicitly or implicitly based on a set of rules that define the
changes that occur in a transition from an old state of a database to a new, updated
state. Therefore, these rules provide the basis of a framework for classifying and
specifying these problems.
In this paper we propose to use the event rules [Oli91], which explicitly define
the insertions and deletions induced by an update, for such a basis. We also define
two interpretations of these rules which provide a common framework for
classifying and specifying deductive database updating problems such as view
updating, materialized view maintenance, integrity constraints checking, integrity
constraints maintenance, repairing inconsistent databases, integrity constraints
satisfiability or condition monitoring. Moreover, these interpretations allow us to
identify and to specify sorne problems that have received little attention up to now
like enforcing or preventing condition activation. By considering only a uniqu~ set
of rules for specifying all these problems, we want to show that it is possible to
provide general methods able to deal with all these problems as a whole
Twelve Theses on Reactive Rules for the Web
Reactivity, the ability to detect and react to events, is an
essential functionality in many information systems. In particular, Web
systems such as online marketplaces, adaptive (e.g., recommender) systems,
and Web services, react to events such as Web page updates or
data posted to a server.
This article investigates issues of relevance in designing high-level programming
languages dedicated to reactivity on the Web. It presents
twelve theses on features desirable for a language of reactive rules tuned
to programming Web and Semantic Web applications
Integrity Constraints in Trust Management
We introduce the use, monitoring, and enforcement of integrity constraints in
trust management-style authorization systems. We consider what portions of the
policy state must be monitored to detect violations of integrity constraints.
Then we address the fact that not all participants in a trust management system
can be trusted to assist in such monitoring, and show how many integrity
constraints can be monitored in a conservative manner so that trusted
participants detect and report if the system enters a policy state from which
evolution in unmonitored portions of the policy could lead to a constraint
violation.Comment: An extended abstract appears in the proc. of the 10th ACM Symp. on
Access Control Models and Technologies (SACMAT). 200
Context-Aware Information Retrieval for Enhanced Situation Awareness
In the coalition forces, users are increasingly challenged with the issues of information overload and correlation of information from heterogeneous sources. Users might need different pieces of information, ranging from information about a single building, to the resolution strategy of a global conflict. Sometimes, the time, location and past history of information access can also shape the information needs of users. Information systems need to help users pull together data from disparate sources according to their expressed needs (as represented by system queries), as well as less specific criteria. Information consumers have varying roles, tasks/missions, goals and agendas, knowledge and background, and personal preferences. These factors can be used to shape both the execution of user queries and the form in which retrieved information is packaged. However, full automation of this daunting information aggregation and customization task is not possible with existing approaches. In this paper we present an infrastructure for context-aware information retrieval to enhance situation awareness. The infrastructure provides each user with a customized, mission-oriented system that gives access to the right information from heterogeneous sources in the context of a particular task, plan and/or mission. The approach lays on five intertwined fundamental concepts, namely Workflow, Context, Ontology, Profile and Information Aggregation. The exploitation of this knowledge, using appropriate domain ontologies, will make it feasible to provide contextual assistance in various ways to the work performed according to a userâs taskrelevant information requirements. This paper formalizes these concepts and their interrelationships
An XML Framework for Integrating Continuous Queries, Composite Event Detection, and Database Condition Monitoring for Multiple Data Streams
With advancements in technology over the last ten years, data management
issues have evolved from a stored persistent form to also include streaming
data generated from sensors and other software monitoring tools.
Furthermore, distributed, event-based systems are becoming more prevalent,
with a need to develop applications that can dynamically respond to information extracted from data streams. This research is investigating the
integration of stream processing and event processing techniques, with
expressive filtering capabilities that include queries over persistent databases
to provide application context to the filtering process. Distributed Event
Processing Agents (DEPAs) continuously filter events from multiple data
streams of different formats that provide XML views. Composite events for
data streams are expressed using the Composite Event Detection Language (CEDL) and mapped to Composite XQuery (CXQ) for implementation. CXQ is a language that extends XQuery with features from CEDL, including operators for expressing sequence, disjunction, conjunction, repetition, aggregation, and time windows for events. Continuous queries and composite event filters are integrated with techniques for materialized view maintenance and
incremental evaluation in condition monitoring to provide efficient ways of
enhancing stream filters with database queries. The filtering and event
detection load is distributed among multiple DEPAs, with CXQ expressions
decomposed to allocate subcomponents of the expression to DEPAs that
efficiently communicate in the global detection of composite events. A unique
aspect of our research is that it extends XQuery with temporal, composite
event features to combine techniques for continuous queries in stream
processing, incremental evaluation in condition monitoring, and detection and
filtering of composite events, creating an expressive environment for the
extraction of meaningful events from multiple data streams with XML views
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