Ontology-Based Data Access (OBDA) is a recent paradigm aiming at enhancing data access by taking ontological knowledge into account. When using existential rules as ontological language, query answering is an undecidable problem, whence numerous decidable classes of ontologies have been defined, ranging from classes with very good computational complexities (AC0 in data complexity) to classes w...

The evaluation of Datalog rules over large Knowledge Graphs (KGs) is essential for many applications. In this paper, we present a new method of materializing Datalog inferences, which combines a column-based memory layout with novel optimization methods that avoid redundant inferences at runtime. The pro-active caching of certain subqueries further increases efficiency. Our empirical evaluation...

In this chapter I argue that in preindustrial societies where resources were difficult to monopolize and physical coercion was not an option, ideology provided a significant source of social power. This avenue toward social power was especially important in the prehispanic Andes, and the establishment and negotiation of that power was often through ritual feasting involving politically charged ...

1 Introduction

A multimedia mediator aims at providing a well-structured gateway to some application dependent part of a federated multimedia system. Our specific design employs proxy objects for external multimedia items and introduces a new concept of semi-structured and self-describing types for multimedia items. Query evaluation and optimization hide all details of communication with external sources and ...

This paper argues for the need to provide more flexibility in the level of service offered by Grid-enable high-performance, parallel, supercomputing resources. It is envisaged that such need could be satisfied by making separate Service Level Agreements (SLAs) between the resource owner and the user who wants to submit and run a job on these resources. A number of issues related to the material...

The wide dissemination and effective materialization of the foreseen benefits of dynamic virtual organizations require a holistic approach to understand, model, and develop the needed infrastructures and tools to support the full life cycle of this organizational paradigm. Under this scope, the ECOLEAD integrated project was launched with the aim of creating the necessary foundations and mechan...

Flood is the flow of water at ground surface that relatively high and cannot be accommodated by drainage canals or rivers, causing inundation in an amount exceeds normal causes harm to humans. This flood disaster usually occurs lowlands around especially rivers have various environmental problems such as factory waste, plastic soil erosion, so on. One often experience these events Citarum River...