Large infrastructures become technologically more and more complex and interdependencies between ... more Large infrastructures become technologically more and more complex and interdependencies between different infrastructures increase. As a consequence complex infrastructures become more vulnerable to emergencies. The personnel in charge must be supported in the challenging task of identifying and assessing an emergency situation and in choosing an appropriate reaction. This calls for a system which continuously analyses the available sensory data for emergency situations, making predictions for the future development of an emergency and recommending proper reactions to the emergency.
Traditional answering methods evaluate queries only against positive and definite knowledge expre... more Traditional answering methods evaluate queries only against positive and definite knowledge expressed by means of facts and deduction rules. They do not make use of negative, disjunctive or existential information. Negative or indefinite knowledge is however often available in knowledge base systems, either as design requirements, or as observed properties. Such knowledge can serve to rule out unproductive subexpressions during query answering. In this article, we propose an approach for constraining any conventional query answering procedure with general, possibly negative or indefinite formulas, so as to discard impossible cases and to avoid redundant evaluations. This approach does not impose additional conditions on the positive and definite knowledge, nor does it assume any particular semantics for negation. It adopts that of the conventional query answering procedure it constrains. This is achieved by relying on meta-interpretation for specifying the constraining process. The ...
This article proposes an approach to rely on the standard operators of relational algebra (includ... more This article proposes an approach to rely on the standard operators of relational algebra (including grouping and ag- gregation) for processing complex event without requiring window specifications. In this way the approach can pro- cess complex event queries of the kind encountered in appli- cations such as emergency management in metro networks. This article presents Temporal Stream Algebra (TSA) which combines the operators of relational algebra with an analy- sis of temporal relations at compile time. This analysis de- termines which relational algebra queries can be evaluated against data streams, i. e. the analysis is able to distinguish valid from invalid stream queries. Furthermore the analysis derives functions similar to the pass, propagation and keep invariants in Tucker's et al. \Exploiting Punctuation Seman- tics in Continuous Data Streams". These functions enable the incremental evaluation of TSA queries, the propagation of punctuations, and garbage collection...
Temporal knowledge representation and reasoning is a major research field in Artificial Intellige... more Temporal knowledge representation and reasoning is a major research field in Artificial Intelligence, in Database Systems, and in Web and Semantic Web research. The ability to model and process time and calendar data is essential for many applications like appointment scheduling, planning, Web services, temporal and active database systems, adaptive Web applications, and mobile computing applications. This article aims at three complementary goals. First, to provide with a general background in temporal data modeling and reasoning approaches. Second, to serve as an orientation guide for further specific reading. Third, to point to new application fields and research perspectives on temporal knowledge representation and reasoning in the Web and Semantic Web.
The application logic of many information systems often follows a given workflow enforcing certai... more The application logic of many information systems often follows a given workflow enforcing certain orders and dependencies of events. This knowledge can be used to make event processing more efficient. To this end Instantiating Hierarchical Timed Automata (IHTA) capturing the knowledge will be formally defined in this work. Later, constraints will be derived from IHTA and used by the semantic query optimisation algorithm.
An increasing adoption of e-commerce requires application systems and their business processes to... more An increasing adoption of e-commerce requires application systems and their business processes to be opened across organizational boundaries for combination with those of other business partners. Businesses offer more and more of their services by means of Web Services which are a standardized way of integrating applications over the Internet in a loosely coupled fashion. Building upon these offered functionalities one is then able to create new functionality by combining existing services into new ones. This combining of ...
Large infrastructures become technologically more and more complex and interdependencies between ... more Large infrastructures become technologically more and more complex and interdependencies between different infrastructures increase. As a consequence complex infrastructures become more vulnerable to emergencies. The personnel in charge must be supported in the challenging task of identifying and assessing an emergency situation and in choosing an appropriate reaction. This calls for a system which continuously analyses the available sensory data for emergency situations, making predictions for the future development of an emergency and recommending proper reactions to the emergency.
Traditional answering methods evaluate queries only against positive and definite knowledge expre... more Traditional answering methods evaluate queries only against positive and definite knowledge expressed by means of facts and deduction rules. They do not make use of negative, disjunctive or existential information. Negative or indefinite knowledge is however often available in knowledge base systems, either as design requirements, or as observed properties. Such knowledge can serve to rule out unproductive subexpressions during query answering. In this article, we propose an approach for constraining any conventional query answering procedure with general, possibly negative or indefinite formulas, so as to discard impossible cases and to avoid redundant evaluations. This approach does not impose additional conditions on the positive and definite knowledge, nor does it assume any particular semantics for negation. It adopts that of the conventional query answering procedure it constrains. This is achieved by relying on meta-interpretation for specifying the constraining process. The ...
This article proposes an approach to rely on the standard operators of relational algebra (includ... more This article proposes an approach to rely on the standard operators of relational algebra (including grouping and ag- gregation) for processing complex event without requiring window specifications. In this way the approach can pro- cess complex event queries of the kind encountered in appli- cations such as emergency management in metro networks. This article presents Temporal Stream Algebra (TSA) which combines the operators of relational algebra with an analy- sis of temporal relations at compile time. This analysis de- termines which relational algebra queries can be evaluated against data streams, i. e. the analysis is able to distinguish valid from invalid stream queries. Furthermore the analysis derives functions similar to the pass, propagation and keep invariants in Tucker's et al. \Exploiting Punctuation Seman- tics in Continuous Data Streams". These functions enable the incremental evaluation of TSA queries, the propagation of punctuations, and garbage collection...
Temporal knowledge representation and reasoning is a major research field in Artificial Intellige... more Temporal knowledge representation and reasoning is a major research field in Artificial Intelligence, in Database Systems, and in Web and Semantic Web research. The ability to model and process time and calendar data is essential for many applications like appointment scheduling, planning, Web services, temporal and active database systems, adaptive Web applications, and mobile computing applications. This article aims at three complementary goals. First, to provide with a general background in temporal data modeling and reasoning approaches. Second, to serve as an orientation guide for further specific reading. Third, to point to new application fields and research perspectives on temporal knowledge representation and reasoning in the Web and Semantic Web.
The application logic of many information systems often follows a given workflow enforcing certai... more The application logic of many information systems often follows a given workflow enforcing certain orders and dependencies of events. This knowledge can be used to make event processing more efficient. To this end Instantiating Hierarchical Timed Automata (IHTA) capturing the knowledge will be formally defined in this work. Later, constraints will be derived from IHTA and used by the semantic query optimisation algorithm.
An increasing adoption of e-commerce requires application systems and their business processes to... more An increasing adoption of e-commerce requires application systems and their business processes to be opened across organizational boundaries for combination with those of other business partners. Businesses offer more and more of their services by means of Web Services which are a standardized way of integrating applications over the Internet in a loosely coupled fashion. Building upon these offered functionalities one is then able to create new functionality by combining existing services into new ones. This combining of ...
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