1,720,972 research outputs found
Inputs, Outputs, and Composition in the Logic of Information Flows
No full textThe logic of information flows (LIF) is a general framework in which tasks of a procedural nature can be modeled in a declarative, logic-based fashion. The first contribution of this paper is to propose semantic and syntactic definitions of inputs and outputs of LIF expressions. We study how the two relate and show that our syntactic definition is optimal in a sense that is made precise. The second contribution is a systematic study of the expressive power of sequential composition in LIF. Our results on composition tie in the results on inputs and outputs, and relate LIF to first-order logic (FO) and bounded-variable LIF to bounded-variable FO.This research received funding from the Flemish Government under the “Onderzoeksprogramma Artificiele Intelli- ¨gentie (AI) Vlaanderen” programme, from FWO Flanders project G0D9616N, and from Natural Sciences and Engineering Research Council of Canada (NSERC). Jan Van den Bussche is partially supported by the National Natural Science Foundation of China (61972455)
Inputs, Outputs, and Composition in the Logic of Information Flows
No full textThe logic of information flows (LIF) is a general framework in which tasks of a procedural nature can be modeled in a declarative, logic-based fashion. The first contribution of this paper is to propose semantic and syntactic definitions of inputs and outputs of LIF expressions. We study how the two relate and show that our syntactic definition is optimal in a sense that is made precise. The second contribution is a systematic study of the expressive power of sequential composition in LIF. Our results on composition tie in the results on inputs and outputs, and relate LIF to first-order logic (FO) and bounded-variable LIF to bounded-variable FO.This research received funding from the Flemish Government under the “Onderzoeksprogramma Artificiele Intelli- ¨gentie (AI) Vlaanderen” programme, from FWO Flanders project G0D9616N, and from Natural Sciences and Engineering Research Council of Canada (NSERC). Jan Van den Bussche is partially supported by the National Natural Science Foundation of China (61972455)
Inputs, outputs, and composition in the logic of information flows
No full textThe logic of information flows (LIF) is a general framework in which tasks of a procedural nature can be modeled in a declarative, logic-based fashion. The first contribution of this paper is to propose semantic and syntactic definitions of inputs and outputs of LIF expressions. We study how the two relate and show that our syntactic definition is optimal in a sense that is made precise. The second contribution is a systematic study of the expressive power of sequential composition in LIF. Our results on composition tie in the results on inputs and outputs, and relate LIF to first-order logic (FO) and bounded-variable LIF to bounded-variable FO. This paper is the extended version of a paper presented at KR 2020 [2].This research received funding from the Flemish Government under the “Onderzoeksprogramma Artificiële Intelligentie (AI) Vlaanderen” programme, from FWO Flanders project G0D9616N, and from Natural Sciences and Engineering Research Council of Canada (NSERC). Jan Van den Bussche is partially supported by the National Natural Science Foundation of China (61972455). Heba Aamer is supported by the Special Research Fund (BOF) (BOF19OWB16)
AOD 2.0: A category based submission add-on for DSpace 4.0
Full text linkPresentation at Open Repositories 2014, Helsinki, Finland, June 9-13, 2014DSpace Interest Group PresentationsThe Institute of Biology of the Southern Seas, Ukraine (IBSS) and Hasselt University (Belgium) are developing with the support of FAO of the United Nations a new version of AgriOcean DSpace named AOD 2.0, as an add-on for DSpace 4.0 and later. It works further on the specifications of AgriOcean DSpace 1.x including the type-based submission module, the use of controlled vocabularies (ASFA, AGROVOC) and an easy-to-install version for Windows. While AgriOcean DSpace 1.x was created as a fully customized version of DSpace 1.7.2, AOD 2.0 is developed with a modular approach. Different stand-alone modules are developed and integrated with DSpace 4.0: Ontology Plug-in, Category-based Submission, Batch Import for Submitter. They are made available as AOD 2.0, an easy-to-install package for Linux and Windows.Goovaerts, Marc (Hasselt University, Belgium)Slipetskyy, Denys (Institute of Biology of the Southern Seas)Subirats, Imma (Food and Agriculture Organizations of the United Nations)Keizer, Johannes (Food and Agriculture Organizations of the United Nations)Leinders, Dirk (Hasselt University, Belgium)Dupriez, Christophe (Destin)Surinx, Dimitri (Hasselt University, Belgium)Gybels, Michelle (Hasselt University, Belgium)Vaelen, Jeroen (Hasselt University, Belgium)Vandesbosch, Niki (Hasselt University, Belgium
Executable First-Order Queries in the Logic of Information Flows
Full text linkThe logic of information flows (LIF) has recently been proposed as a general framework in the field of knowledge representation. In this framework, tasks of procedural nature can still be modeled in a declarative, logic-based fashion. In this paper, we focus on the task of query processing under limited access patterns, a well-studied problem in the database literature. We show that LIF is well-suited for modeling this task. Toward this goal, we introduce a variant of LIF called forward LIF (FLIF), in a first-order setting. FLIF takes a novel graph-navigational approach; it is an XPath-like language that nevertheless turns out to be equivalent to the executable fragment of first-order logic defined by Nash and Ludäscher. One can also classify the variables in FLIF expressions as inputs and outputs. Expressions where inputs and outputs are disjoint, referred to as io-disjoint FLIF expressions, allow a particularly transparent translation into algebraic query plans that respect the access limitations. Finally, we show that general FLIF expressions can always be put into io-disjoint form
A Framework for Comparing Query Languages in Their Ability to Express Boolean Queries
No full textWhen a relational database is queried, the result is normally a relation.
Some queries, however, only require a yes/no answer; such
queries are often called boolean queries. In this thesis, we introduce a framework along which we can investigate boolean queries.
We introduce three natural base modalities: testing for nonemptiness of a query; testing for
emptiness; and testing for the containment of the result of one
query in the result of another query. For the class of
first-order queries, these three modalities have exactly the same
expressive power. For other classes of queries, e.g., expressed
in weaker query languages, the modalities may differ in
expressiveness. The expressive power under these different modalities can be compared in several different themes, e.g., we can compare a fixed query language F under emptiness to F under nonemptiness. We introduce four general themes to compare the base modalities:
(1) We identify crucial query features that enable us to go from one modality to
another for a fixed query language. Furthermore, we identify semantical
properties that reflect the lack of these query features to establish
separations.
(2) We compare the expressive power of the base modalities by comparing
different query languages under fixed modalities.
(3) We compare the expressive power of different query languages under
different modalities.
(4) We investigate the closure of the modalities under the boolean connectives.
For each of these themes, we establish subsumption as well as separation results for well known query languages such as conjunctive queries and navigational graph query languages
Navigational Query Languages
No full textIn this thesis we introduce navigational query languages on graphs. Path queries in our languages are built over several operators: identity, union, composition, projection, coprojection, converse, transitive closure, diversity, intersection and difference. The smallest language we will consider only contains the first 3 operators, while the largest language contains all operators. For these query languages we will characterize their complete relative expressive power, i.e., we will compare the expressive power of languages containing different selections of operators.
In these query languages we will also model boolean queries by associating nonempty query results with true and empty query results with false. As for path queries, we will for these boolean queries characterize the complete relative expressive power of our languages. On the other hand, we will also consider other approaches to model boolean queries in our languages and characterize their expressive power
A Framework for Comparing Query Languages in Their Ability to Express Boolean Queries
No full textWhen a relational database is queried, the result is normally a relation.
Some queries, however, only require a yes/no answer; such
queries are often called boolean queries. In this thesis, we introduce a framework along which we can investigate boolean queries.
We introduce three natural base modalities: testing for nonemptiness of a query; testing for
emptiness; and testing for the containment of the result of one
query in the result of another query. For the class of
first-order queries, these three modalities have exactly the same
expressive power. For other classes of queries, e.g., expressed
in weaker query languages, the modalities may differ in
expressiveness. The expressive power under these different modalities can be compared in several different themes, e.g., we can compare a fixed query language F under emptiness to F under nonemptiness. We introduce four general themes to compare the base modalities:
(1) We identify crucial query features that enable us to go from one modality to
another for a fixed query language. Furthermore, we identify semantical
properties that reflect the lack of these query features to establish
separations.
(2) We compare the expressive power of the base modalities by comparing
different query languages under fixed modalities.
(3) We compare the expressive power of different query languages under
different modalities.
(4) We investigate the closure of the modalities under the boolean connectives.
For each of these themes, we establish subsumption as well as separation results for well known query languages such as conjunctive queries and navigational graph query languages
Navigational Query Languages
No full textIn this thesis we introduce navigational query languages on graphs. Path queries in our languages are built over several operators: identity, union, composition, projection, coprojection, converse, transitive closure, diversity, intersection and difference. The smallest language we will consider only contains the first 3 operators, while the largest language contains all operators. For these query languages we will characterize their complete relative expressive power, i.e., we will compare the expressive power of languages containing different selections of operators.
In these query languages we will also model boolean queries by associating nonempty query results with true and empty query results with false. As for path queries, we will for these boolean queries characterize the complete relative expressive power of our languages. On the other hand, we will also consider other approaches to model boolean queries in our languages and characterize their expressive power
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