15,208 research outputs found
RDF Querying
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
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
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
Rule-Based Composite Event Queries
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
Twelve Theses on Reactive Rules for the Web
Reactivity, the ability to detect events and respond to them
automatically through reactive programs, is a key requirement in many
present-day information systems. Work on Web Services re
ects the need
for support of reactivity on a higher abstraction level than just message
exchange by HTTP. This article presents the composite event query facilities
of the reactive rule-based programming language XChange. Composite
events are important in the dynamic world of the Web where
applications, or Web Services, that have not been engineered together
are composed and have to cooperate by exchanging event messages
Reactivity on the Web
Reactivity, the ability to detect simple and composite events and respond in a timely
manner, is an essential requirement in many present-day information systems. With
the emergence of new, dynamic Web applications, reactivity on the Web is receiving
increasing attention. Reactive Web-based systems need to detect and react not only
to simple events but also to complex, real-life situations. This paper introduces
XChange, a language for programming reactive behaviour on the Web, emphasising
the querying of event data and detection of composite events
Use-cases on evolution
This report presents a set of use cases for evolution and reactivity for data in the Web and
Semantic Web. This set is organized around three different case study scenarios, each of them
is related to one of the three different areas of application within Rewerse. Namely, the scenarios
are: “The Rewerse Information System and Portal”, closely related to the work of A3
– Personalised Information Systems; “Organizing Travels”, that may be related to the work
of A1 – Events, Time, and Locations; “Updates and evolution in bioinformatics data sources”
related to the work of A2 – Towards a Bioinformatics Web
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
State-of-the-art on evolution and reactivity
This report starts by, in Chapter 1, outlining aspects of querying and updating resources on
the Web and on the Semantic Web, including the development of query and update languages
to be carried out within the Rewerse project.
From this outline, it becomes clear that several existing research areas and topics are of
interest for this work in Rewerse. In the remainder of this report we further present state of
the art surveys in a selection of such areas and topics. More precisely: in Chapter 2 we give
an overview of logics for reasoning about state change and updates; Chapter 3 is devoted to briefly describing existing update languages for the Web, and also for updating logic programs;
in Chapter 4 event-condition-action rules, both in the context of active database systems and
in the context of semistructured data, are surveyed; in Chapter 5 we give an overview of some relevant rule-based agents frameworks
Enabling Personalized Composition and Adaptive Provisioning of Web Services
The proliferation of interconnected computing devices is fostering the emergence of environments where Web services made available to mobile users are a commodity. Unfortunately, inherent limitations of mobile devices still hinder the seamless access to Web services, and their use in supporting complex user activities. In this paper, we describe the design and implementation of a distributed, adaptive, and context-aware framework for personalized service composition and provisioning adapted to mobile users. Users specify their preferences by annotating existing process templates, leading to personalized service-based processes. To cater for the possibility of low bandwidth communication channels and frequent disconnections, an execution model is proposed whereby the responsibility of orchestrating personalized processes is spread across the participating services and user agents. In addition, the execution model is adaptive in the sense that the runtime environment is able to detect exceptions and react to them according to a set of rules
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