20 results on '"Complex objects"'
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2. АЛГОРИТМ ПРЕДСТАВЛЕНИЯ СВОЙСТВ ОБЪЕКТОВ ЭКСПЕРТНОЙ СИСТЕМЫ
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intelligent systems ,сложные объекты ,нечеткость ,knowledge ,complex objects ,интеллектуальные системы ,экспертные системы ,membership function ,знания ,expert systems ,fuzziness ,функция принадлежности - Abstract
Рассматривается проблема представления свойств сложных объектов в базах знаний экспертных систем, когда они характеризуются неопределенностью и отсутствуют способы оценки каких либо значений размытости их количественных характеристик, что существенно затрудняет исследование соответствующего признакого пространства. Анализ поставленной задачи свидетельствует о целесообразности изначальной ориентации програмного обеспечения ее решения на многозначную интерпретацию с позиции нечеткого и лингвистического моделирования рассматриваемой проблемной области., The article considers the problem of presenting the properties of complex objects in the knowledge bases of expert systems when they are characterized by uncertainty, and there is no other way to estimate ambiguity values of their quantitative characteristics, which complicates the study of the corresponding attribute space. The analysis of the task set testifies to the expediency of the initial orientation of the software for its solution to the multi-valued interpretation from the position of fuzzy and linguistic modeling of the problem area under consideration., №4(82) (2019)
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- 2019
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3. Processing of data from complex objects through pattern recognition methods
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Mariya Ivanova Konsulova Bakalova
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complex objects ,Computer science ,business.industry ,pattern recognition ,Scale-invariant feature transform ,Pattern recognition ,statistical processing ,General Medicine ,Pattern recognition (psychology) ,lcsh:Technology (General) ,lcsh:T1-995 ,Artificial intelligence ,Statistical processing ,business - Abstract
In the description of complex objects, we need methods which could reflect the complex interconnections between components and sift out if possible those of them which are substantial for the specific application. It is offered in this publication the pattern recognition methods should be used as a unified method for processing of data from complex objects. The proposed algorithm may be used in the recognition of the condition of objects of various nature. The indicated examples prove the practical applicability of the methodology as they represent the solution of specific practical problems.
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- 2018
4. Design, Implementation and Analysis of a Description Model for Complex Archaeological Objects
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Ozturk, Aybuke and STAR, ABES
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Ceramics ,Entrepôts de données ,OLAP ,Clustering ensembliste ,Clustering de partitions combinées ,Combined Partition Clustering ,Validité des clusters ,Initialisation linéaire MaxMin ,Bases de données ,Céramique ,Cluster Validity ,Data Warehouses ,Clustering ,Archaeometry ,MaxMin Linear Initialization ,Databases ,Archaeology ,Archéologie ,Archéométrie ,Visual TSFD ,[INFO.INFO-DB] Computer Science [cs]/Databases [cs.DB] ,Objets complexes ,Cluster Ensemble ,Complex Objects - Abstract
Ceramics are one of the most important archaeological materials to help in the reconstruction of past civilizations. Information about complex ceramic objects is composed of textual, numerical and multimedia data, which induce several research challenges addressed in this thesis. From a technical perspective, ceramic databases have different file formats, access protocols and query languages. From a data perspective, ceramic data are heterogeneous and experts have differentways of representing and storing data. There is no standardized content and terminology, especially in terms of description of ceramics. Moreover, data navigation and observation are difficult. Data integration is also difficult due to the presence of various dimensions from distant databases, which describe the same categories of objects in different ways.Therefore, the research project presented in this thesis aims to provide archaeologists and archaeological scientists with tools for enriching their knowledge by combining different information on ceramics. We divide our work into two complementary parts: (1) Modeling of Complex Archaeological Data and (2) Clustering Analysis of Complex Archaeological Data. The first part of this thesis is dedicated to the design of a complex archaeological database model for the storage of ceramic data. This database is also used to source a data warehouse for doing online analytical processing (OLAP). The second part of the thesis is dedicated to an in-depth clustering (categorization) analysis of ceramic objects. To do this, we propose a fuzzy approach, where ceramic objects may belong to more than one cluster (category). Such a fuzzy approach is well suited for collaborating with experts, by opening new discussions based on clustering results.We contribute to fuzzy clustering in three sub-tasks: (i) a novel fuzzy clustering initialization method that keeps the fuzzy approach linear; (ii) an innovative quality index that allows finding the optimal number of clusters; and (iii) the Multiple Clustering Analysis approach that builds smart links between visual, textual and numerical data, which assists in combining all types ofceramic information. Moreover, the methods we propose could also be adapted to other application domains such as economy or medicine., La céramique est l'un des matériaux archéologiques les plus importants pour aider à la reconstruction des civilisations passées. Les informations à propos des objets céramiques complexes incluent des données textuelles, numériques et multimédias qui posent plusieurs défis de recherche abordés dans cette thèse. D'un point de vue technique, les bases de données de céramiques présentent différents formats de fichiers, protocoles d'accès et langages d'interrogation. Du point de vue des données, il existe une grande hétérogénéité et les experts ont différentes façons de représenter et de stocker les données. Il n'existe pas de contenu et de terminologie standard, surtout en ce qui concerne la description des céramiques. De plus, la navigation et l'observation des données sont difficiles. L'intégration des données est également complexe en raison de laprésence de différentes dimensions provenant de bases de données distantes, qui décrivent les mêmes catégories d'objets de manières différentes.En conséquence, ce projet de thèse vise à apporter aux archéologues et aux archéomètres des outils qui leur permettent d'enrichir leurs connaissances en combinant différentes informations sur les céramiques. Nous divisons notre travail en deux parties complémentaires : (1) Modélisation de données archéologiques complexes, et (2) Partitionnement de données (clustering) archéologiques complexes. La première partie de cette thèse est consacrée à la conception d'un modèle de données archéologiques complexes pour le stockage des données céramiques. Cette base de donnée alimente également un entrepôt de données permettant des analyses en ligne (OLAP). La deuxième partie de la thèse est consacrée au clustering (catégorisation) des objets céramiques. Pour ce faire, nous proposons une approche floue, dans laquelle un objet céramique peut appartenir à plus d'un cluster (d'une catégorie). Ce type d'approche convient bien à la collaboration avec des experts, enouvrant de nouvelles discussions basées sur les résultats du clustering.Nous contribuons au clustering flou (fuzzy clustering) au sein de trois sous-tâches : (i) une nouvelle méthode d'initialisation des clusters flous qui maintient linéaire la complexité de l'approche ; (ii) un indice de qualité innovant qui permet de trouver le nombre optimal de clusters ; et (iii) l'approche Multiple Clustering Analysis qui établit des liens intelligents entre les données visuelles, textuelles et numériques, ce qui permet de combiner tous les types d'informations sur les céramiques. Par ailleurs, les méthodes que nous proposons pourraient également être adaptées à d'autres domaines d'application tels que l'économie ou la médecine.
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- 2018
5. Opportunity for verbalization does not improve visual change detection performance: A state-trace analysis
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Richard D. Morey, Melissa Prince, Candice C. Morey, Florian Sense, Andrew Heathcote, and Psychometrics and Statistics
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Male ,Visual perception ,FEATURES ,COMPLEX OBJECTS ,Task (project management) ,State-trace ,0302 clinical medicine ,Developmental and Educational Psychology ,GeneralLiterature_REFERENCE(e.g.,dictionaries,encyclopedias,glossaries) ,Psychology(all) ,General Psychology ,INTERFERENCE ,SHORT-TERM-MEMORY ,05 social sciences ,Memory, Short-Term ,Verbalization ,Visual Perception ,ComputingMethodologies_DOCUMENTANDTEXTPROCESSING ,Change detection ,Female ,Psychology (miscellaneous) ,Articulation (phonetics) ,Psychology ,Cognitive psychology ,STORAGE ,Adult ,Articulatory suppression ,BF ,Short-term memory ,Experimental and Cognitive Psychology ,Article ,050105 experimental psychology ,CAPACITY ,Young Adult ,03 medical and health sciences ,BINDING DEFICITS ,WORKING-MEMORY ,Arts and Humanities (miscellaneous) ,Encoding (memory) ,Humans ,0501 psychology and cognitive sciences ,Verbal Behavior ,Working memory ,ATTENTION ,Bayes Theorem ,Working memory capacity ,MAINTENANCE ,Photic Stimulation ,030217 neurology & neurosurgery - Abstract
Evidence suggests that there is a tendency to verbally recode visually-presented information, and that in some cases verbal recoding can boost memory performance. According to multi-component models of working memory, memory performance is increased because task-relevant information is simultaneously maintained in two codes. The possibility of dual encoding is problematic if the goal is to measure capacity for visual information exclusively. To counteract this possibility, articulatory suppression is frequently used with visual change detection tasks specifically to prevent verbalization of visual stimuli. But is this precaution always necessary? There is little reason to believe that concurrent articulation affects performance in typical visual change detection tasks, suggesting that verbal recoding might not be likely to occur in this paradigm, and if not, precautionary articulatory suppression would not always be necessary. We present evidence confirming that articulatory suppression has no discernible effect on performance in a typical visual change-detection task in which abstract patterns are briefly presented. A comprehensive analysis using both descriptive statistics and Bayesian state-trace analysis revealed no evidence for any complex relationship between articulatory suppression and performance that would be consistent with a verbal recoding explanation. Instead, the evidence favors the simpler explanation that verbal strategies were either not deployed in the task or, if they were, were not effective in improving performance, and thus have no influence on visual working memory as measured during visual change detection. We conclude that in visual change detection experiments in which abstract visual stimuli are briefly presented, pre-cautionary articulatory suppression is unnecessary.
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- 2017
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6. Haptically guided grasping. FMRI shows right-hemisphere parietal stimulus encoding, and bilateral dorso-ventral parietal gradients of object- and action-related processing during grasp execution
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Gregory Króliczak, Mattia Marangon, Agnieszka Kubiak, Marangon M, Kubiak A, and Kroliczak G
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complex objects ,Brain activity and meditation ,Posterior parietal cortex ,Kinematics ,Stimulus (physiology) ,Insular cortex ,behavioral disciplines and activities ,050105 experimental psychology ,lcsh:RC321-571 ,03 medical and health sciences ,Behavioral Neuroscience ,0302 clinical medicine ,haptic exploration ,medicine ,action planning ,0501 psychology and cognitive sciences ,Computer vision ,dorsalstream ,lcsh:Neurosciences. Biological psychiatry. Neuropsychiatry ,Biological Psychiatry ,Original Research ,Haptic technology ,grasp execution ,medicine.diagnostic_test ,business.industry ,05 social sciences ,GRASP ,body regions ,Psychiatry and Mental health ,haptic exploration, encoding bias,action planning, grasp execution, complex objects, dorsalstream ,Neuropsychology and Physiological Psychology ,dorsal stream ,Neurology ,Artificial intelligence ,encoding bias ,business ,Functional magnetic resonance imaging ,Psychology ,030217 neurology & neurosurgery ,psychological phenomena and processes ,Neuroscience - Abstract
The neural bases of haptically-guided grasp planning and execution are largely unknown, especially for stimuli having no visual representations. Therefore, we used functional magnetic resonance imaging (fMRI) to monitor brain activity during haptic exploration of novel 3D complex objects, subsequent grasp planning, and the execution of the pre-planned grasps. Haptic object exploration, involving extraction of shape, orientation, and length of the to-be-grasped targets, was associated with the fronto-parietal, temporo-occipital, and insular cortex activity. Yet, only the anterior divisions of the posterior parietal cortex (PPC) of the right hemisphere were significantly more engaged in exploration of complex objects (vs. simple control disks). None of these regions were re-recruited during the planning phase. Even more surprisingly, the left-hemisphere intraparietal, temporal, and occipital areas that were significantly invoked for grasp planning did not show sensitivity to object features. Finally, grasp execution, involving the re-recruitment of the critical right-hemisphere PPC clusters, was also significantly associated with two kinds of bilateral parieto-frontal processes. The first represents transformations of grasp-relevant target features and is linked to the dorso-dorsal (lateral and medial) parieto-frontal networks. The second monitors grasp kinematics and belongs to the ventro-dorsal networks. Indeed, signal modulations associated with these distinct functions follow dorso-ventral gradients, with left aIPS showing significant sensitivity to both target features and the characteristics of the required grasp. Thus, our results from the haptic domain are consistent with the notion that the parietal processing for action guidance reflects primarily transformations from object-related to effector-related coding, and these mechanisms are rather independent of sensory input modality.
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- 2016
7. Managing multi-platform materials: selected case studies
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Langley, Somaya, Carter, Trevor, Davies, Matthew, and Gilmour, Ian
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Digital Archiving ,Digital Preservation ,Case Studies ,Apps ,Multi-Platform ,Complex Objects - Abstract
Mobile devices and Internet usage are now common in most parts of the world. Archives and other cultural agencies are challenged by the increasing amounts, and complexity, of digital content. New strategies are being developed and promoted to enable digital acquisition and preservation. The National Film and Sound Archive of Australia (NFSA) is examining and addressing acquisition and preservation challenges for a range of complex digital content, within available resources. This paper will discuss issues associated with a range of multi-platform content with reference to selected case studies.
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- 2013
8. Supporting Sensemaking of Complex Objects with Visualizations: Visibility and Complementarity of Interactions
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Paul Parsons, Jim Morey, Hai-Ning Liang, and Kamran Sedig
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complex objects ,human–information interaction ,Computer Networks and Communications ,Computer science ,usability evaluation ,02 engineering and technology ,Interaction design ,mixed-methods study ,Human–computer interaction ,0202 electrical engineering, electronic engineering, information engineering ,Interface design ,interaction techniques ,visualization ,complementarity ,lcsh:T58.5-58.64 ,lcsh:Information technology ,business.industry ,Communication ,05 social sciences ,External representation ,interaction design ,050301 education ,sensemaking ,020207 software engineering ,Usability ,Cognition ,visibility ,Sensemaking ,4D structures ,Complementarity (physics) ,Visualization ,Human-Computer Interaction ,interface design ,business ,Library and Information Science ,0503 education - Abstract
Making sense of complex objects is difficult, and typically requires the use of external representations to support cognitive demands while reasoning about the objects. Visualizations are one type of external representation that can be used to support sensemaking activities. In this paper, we investigate the role of two design strategies in making the interactive features of visualizations more supportive of users’ exploratory needs when trying to make sense of complex objects. These two strategies are visibility and complementarity of interactions. We employ a theoretical framework concerned with human–information interaction and complex cognitive activities to inform, contextualize, and interpret the effects of the design strategies. The two strategies are incorporated in the design of Polyvise, a visualization tool that supports making sense of complex four-dimensional geometric objects. A mixed-methods study was conducted to evaluate the design strategies and the overall usability of Polyvise. We report the findings of the study, discuss some implications for the design of visualization tools that support sensemaking of complex objects, and propose five design guidelines. We anticipate that our results are transferrable to other contexts, and that these two design strategies can be used broadly in visualization tools intended to support activities with complex objects and information spaces.
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- 2016
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9. Joining distributed complex objects
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Distributed databases ,Join operation ,Storage structures ,DB-DFDB: DISTRIBUTED OR FEDERATED DATABASES ,Performance aspects ,Complex objects ,InformationSystems_DATABASEMANAGEMENT - Abstract
The performance of a non-standard distributed database system is strongly ifluenced by complex objects. The effective exploitation of parallelism in querying them and a suitable structure to store them are required in order to obtain acceptable response times in these database environments where performance tends to be critical. In this paper we use an hierarchical complex object model with object references and define several join operations for these complex objects which we will call tuple objects. These join queries for tuple-objects can be categorized into materialized, functional and value-based joins. An analytical performance evaluation gives insight into which distributed storage structures for tuple-objects are most effective with regard to executing the different kinds of tuple-object joins.
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- 1992
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10. Deux modèles de fondation dans les Recherches logiques
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Thomas Nenon
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objets ,complex objects ,ontologique ,intuition sensible ,conscience ,species ,phénoménologie ,Klein Jacob ,Heidegger ,consciousness ,philosophie transcendantale ,Husserl ,intuition catégoriale ,intuition ,lcsh:P1-1091 ,fondation ,essences ,passivity ,ontology ,judgment ,ontologie ,mind ,time ,langage ,categorial intuition ,epistemological ,mathematics ,objets dépendants ,donation ,passivité ,logique ,General Medicine ,philosophie contemporaine ,body ,philosophie ancienne ,Kant ,corps ,nombres ,temps ,phenomenology ,ontological ,dependant objects ,ancient philosophy ,gnoséologique ,objets indépendants ,éidétique ,substance ,Mind ,incarnation ,foundation ,objets simples ,Aristotle ,transcendental philosophy ,esprit ,concrete contents ,logic ,language ,sensible intuition ,Augustine ,mathématique ,plasticité ,Aristote ,lcsh:Philology. Linguistics ,objets complexes ,contenus concrets ,plasticity ,Augustin d'Hippone ,numeration ,espèces ,simple objects ,givenness ,contenus abstraits ,independant objects ,jugement ,imagination ,abstract contents - Abstract
Cette étude essaye d’établir qu’il y a deux notions très différentes de « fondation » à l’œuvre dans les Recherches logiques de Husserl. Dans la IIIème Recherche, où le terme est formellement introduit, lorsqu’il se demande quels sont les contenus qui peuvent exister d’une manière autonome (indépendants) et lesquels peuvent exister uniquement en tant que moments d’autre chose (dépendants), Husserl suit ce que j’appelle un « modèle ontologique ». Selon ce modèle, le concret possède une priorité sur à l’abstrait qui est fondé en lui. Dans la VIème Recherche, en revanche, Husserl s’oriente principalement sur un « modèle gnoséologique » qui voit le complexe comme fondé sur ce qui est relativement simple, étant donné que les expériences d’ordre supérieur (telles les perceptions de types d’objets plus complexes) sont « fondées sur » des expériences plus simples, bien qu’elles ne puissent pas y être réduites. L’exemple principal ici est celui des intuitions catégoriales : fondées sur les intuitions sensibles, elles n’y sont pas réductibles. Mais cette distinction entre deux sens différents du terme de « fondation » peut également nous aider à mieux comprendre de nombreuses thèses husserliennes plutôt controversées. Par exemple, elle peut nous permettre de mieux comprendre dans quelle mesure faire l’expérience d’un être humain comme un tout se fonde sur l’expérience d’un corps physique, et cela même si l’étant que nous rencontrons inclut à la fois des aspects corporels et des aspects spirituels – les deux étant vus, d’une manière essentielle, comme des moments de cette unique personne qui fait l’objet de notre expérience.This essay attempts to establish that there are two very different notions of “foundation” at work in Husserl’s Logical Investigation. In the Third Investigation where the term is formally introduced, Husserl is using what I call an « ontological model » that investigates what kinds of contents can exist on their own (independently) and what kinds can exist only as a moment of something else (dependently). According to this model, the concrete has priority over the abstract that is founded upon it. In the Sixth Logical Investigation, by contrast, Husserl orients himself primarily on an « epistemological model » that see the complex as founded upon the relatively simple because they higher-order experiences, e.g. the perceptions of more complex kinds of objects are “founded in” although not reducible to the simpler experiences on which they are founded. The primary example here is that of categorical intuitions that are founded upon, but not reducible to sense intuitions. Distinguishing these two different senses of the term can help us understand better many controversial Husserlian claims, for instance about the way that the experience of the human being as a whole is founded upon the experience of a physical body, even though the entity we encounter includes both bodily and spiritual aspects that are both essentially viewed as moments of the human person who is the object of our experience
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- 2009
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11. Defining the Semantics of Conceptual Modeling Concepts for 3D Complex Objects in Virtual Reality
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Frederic Kleinermann, Olga De Troyer, Wesley Bille, Spaccapietra, S., Delcambre, L., and Web and Information System Engineering
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conceptual Modeling ,complex objects ,Programming language ,Computer science ,media_common.quotation_subject ,formal specifications ,F-logic ,Virtual reality ,computer.software_genre ,Metaverse ,Abstraction layer ,Unified Modeling Language ,Conceptual design ,Human–computer interaction ,Formal specification ,VR-WISE ,Conceptual model ,virtual reality ,F-Logic ,semantics ,computer ,computer.programming_language ,media_common - Abstract
Virtual Reality (VR) allows creating interactive three-dimen sional computer worlds in which objects have a sense of spatial and physical presence and can be manipulated by the user as such. Different software tools have been developed to build virtual worlds. However, most tools require considerable background knowledge about VR and the virtual world needs to be expressed in low-level VR primitives. This is one of the reasons why developing a virtual world is complex, time-consuming and expensive. Introducing a conceptual design phase in the development process will reduce the complexity and provides an abstraction layer to hide the VR implementation details. However, virtual worlds contain features not present in classical software. Therefore, new modeling concepts, currently not available in classical conceptual modeling languages, such as ORM or UML, are required. Next to introducing these new modeling concepts, it is also necessary to define their semantics to ensure unambiguousness and to allow code generation. In this paper, we introduce conceptual modeling concepts to specify complex connected 3D objects. Their semantics are defined using F-logic, a full-fledged logic following the object-oriented paradigm. F-logic will allow applying reasoners to check the consistency of the specifications and to investigate properties before the application is actually built.
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- 2009
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12. Well-definedness and semantic type-checking for the nested relational calculus
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Dirk Van Gucht, Stijn Vansummeren, and Jan Van den Bussche
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Option type ,General Computer Science ,Computer science ,Semantics (computer science) ,0102 computer and information sciences ,02 engineering and technology ,computer.software_genre ,Semantics ,01 natural sciences ,Data type ,Semantic type-checking ,Theoretical Computer Science ,Unit type ,Query equivalence ,0202 electrical engineering, electronic engineering, information engineering ,Complex objects ,Void type ,Type conversion ,Programming language ,Expression (computer science) ,Relational calculus ,Type checking ,010201 computation theory & mathematics ,TheoryofComputation_LOGICSANDMEANINGSOFPROGRAMS ,020201 artificial intelligence & image processing ,Well-definedness ,computer ,Computer Science(all) ,complex objects ,query equivalence ,semantic type-checking ,well-definedness - Abstract
The well-definedness problem for a programming language consists of checking, given an expression and an input type, whether the semantics of the expression is defined for all inputs adhering to the input type. A related problem is the semantic type-checking problem which consists of checking, given an expression, an input type, and an output type whether the expression always returns outputs adhering to the output type on inputs adhering to the input type. Both problems are undecidable for general-purpose programming languages. In this paper we study these problems for the Nested Relational Calculus, a specific-purpose database query language. We also investigate how these problems behave in the presence of prograrruning language features such as singleton coercion and type tests. (c) 2006 Elsevier B.V. All rights reserved.
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- 2007
13. Ciências em trânsito, objetos complexos: práticas e discursos socioambientais
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Dimas Floriani
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complex objects ,environmental epistemology and social theory ,epistemologia ambiental e teoria social ,General Social Sciences ,ciências em trânsito ,objetos complexos ,moving sciences ,General Environmental Science - Abstract
O artigo aborda a discussão sobre epistemologia ambiental e teoria social, considerando o conflito entre os modelos tradicionais de ciência e os atuais, em transição. O conflito da modernidade tecno-científica se expressa também pela imposição de padrões hegemônicos na produção de conhecimento e pelos estilos de vida decorrentes desses padrões. O principal desafio para viabilizar um novo diálogo de saberes é inserir esse debate no interior de um pensamento complexo em construção, que exige novos olhares e práticas epistemológicas, filosóficas e políticas. This paper focuses on the contemporary debate between epistemological conditions of knowledge and social and cultural understanding of these conditions, considering the mutual influences given by the historical context in which both occur. First of all, the traditional view of science is supported by the disciplinary system that reinforces the fragmented conception about social and natural things or ideas; on the other hand, we observe a strong opposition against that former standpoint from supporters of a new philosophical, political and epistemological vision about social and environmental issues, attached to a thought of complexity.
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- 2006
14. New Knowledge Obtaining in Structural-predicate Models of Knowledge
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Koval, Valeriy and Kuk, Yuriy
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Primary Objects ,New Knowledge ,Maximal Discernibleness ,Predicates ,Complex Objects - Abstract
An effective mathematical method of new knowledge obtaining on the structure of complex objects with required properties is developed. The method comprehensively takes into account information on the properties and relations of primary objects, composing the complex objects. It is based on measurement of distances between the predicate groups with some interpretation of them. The optimal measure for measurement of these distances with the maximal discernibleness of different groups of predicates is constructed. The method is tested on solution of the problem of obtaining of new compound with electro-optical properties.
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- 2005
15. The finite difference time domain method on a massively parallel computer
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Ewijk, L.J. van and TNO Fysisch en Elektronisch Laboratorium
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Finite difference time domain method ,Massively parallel computers ,Physics ,Time domain analysis ,Efficiency ,Supercomputers ,Problem size ,Computational electromagnetics ,Electronics laboratories ,Complex objects ,FDTD codes ,Parallel implementations ,Electromagnetic scattering ,Optimisations - Abstract
At the Physics and Electronics Laboratory TNO much research is done in the field of computational electromagnetics (CEM). One of the tools in this field is the Finite Difference Time Domain method (FDTD), a method that has been implemented in a program in order to be able to compute electromagnetic scattering by complex objects. In this paper a parallel implementation of the FDTD code is presented. The implementation is used to investigate the efficiency of the code and to investigate the usefulness of such a parallel implementation, especially with respect to increase in problem size and speed up when compared to a conventional supercomputer. Results of some test computations were compared with results of computations performed on a Convex C230 supercomputer, which indicated a efficiency of 70% and a possible speed up of 4.7 times, with respect to the Convex C230. Current work is on the optimisation of the parallel implementation. © Springer-Verlag Berlin Heidelberg 1996.
- Published
- 1996
16. The finite difference time domain method on a massively parallel computer
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Finite difference time domain method ,Massively parallel computers ,Physics ,Time domain analysis ,Efficiency ,Supercomputers ,Problem size ,Computational electromagnetics ,Electronics laboratories ,Complex objects ,FDTD codes ,Parallel implementations ,Electromagnetic scattering ,Optimisations - Abstract
At the Physics and Electronics Laboratory TNO much research is done in the field of computational electromagnetics (CEM). One of the tools in this field is the Finite Difference Time Domain method (FDTD), a method that has been implemented in a program in order to be able to compute electromagnetic scattering by complex objects. In this paper a parallel implementation of the FDTD code is presented. The implementation is used to investigate the efficiency of the code and to investigate the usefulness of such a parallel implementation, especially with respect to increase in problem size and speed up when compared to a conventional supercomputer. Results of some test computations were compared with results of computations performed on a Convex C230 supercomputer, which indicated a efficiency of 70% and a possible speed up of 4.7 times, with respect to the Convex C230. Current work is on the optimisation of the parallel implementation. © Springer-Verlag Berlin Heidelberg 1996.
- Published
- 1996
17. Set-Oriented retrieval of complex objects in inheritance hierarchies
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Cacace, F., Samarati, P., and Tanca, Letizia
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transitive closure ,ISA hierarchy ,complex objects ,Object-oriented data models - Published
- 1995
18. Joining distributed complex objects: Joining distributed complex objects
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Teeuw, Wouter B., Blanken, Henk M., and Databases (Former)
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Distributed databases ,Join operation ,Storage structures ,DB-DFDB: DISTRIBUTED OR FEDERATED DATABASES ,Performance aspects ,Complex objects ,InformationSystems_DATABASEMANAGEMENT - Abstract
The performance of a non-standard distributed database system is strongly ifluenced by complex objects. The effective exploitation of parallelism in querying them and a suitable structure to store them are required in order to obtain acceptable response times in these database environments where performance tends to be critical. In this paper we use an hierarchical complex object model with object references and define several join operations for these complex objects which we will call tuple objects. These join queries for tuple-objects can be categorized into materialized, functional and value-based joins. An analytical performance evaluation gives insight into which distributed storage structures for tuple-objects are most effective with regard to executing the different kinds of tuple-object joins.
- Published
- 1992
19. Group-Oriented Discretionary Access Controls for Distributed Structurally Object-Oriented Database Systems
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Kelter, Udo
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Buch ,object-oriented databases ,distributed databases ,shared objects ,complex objects ,denial of access ,group paradigms ,discretionary access controls ,hierarchical groups ,ddc:004 - Abstract
Structurally object-oriented database systems [Di86] are a new class of dedicated data storage systems which are intended to be a basis of CAD, CASE, and other design environments which shall support large development teams. This paper presents a concept for discretionary access controls for structurally object-oriented database systems. lt addresses two particular problems: A distinguishing feature of the data model of structurally object-oriented database systems are complex objects. Complex objects are nested and can overlap, i.e. they can share components. Arbitrary complex objects should be units of access control. Shared components cause particular problems because the objects in which they are contained might have contradicting access rights. This problem is solved by introducing certain constraints on the way in which access rights can be granted or denied. A second major problem results from the organization of development projects which use design environments: typically, this is a hierarchy of nested groups. Our concept is group-oriented in the sense that it supports such subgroup hierarchies. Two different interpretations of a subgroup structure, termed group paradigms, are supported. Under one paradigm, a group is used to give several users the same rights, whereas under the other paradigm a group has the set of rights which corresponds to the task of the group. Two final noteworthy features of our concept are that it employs a 4-valued logic which supports explicit denials of access and that it makes provision for distribution of the database.
- Published
- 1990
20. A synthesis of complex objects and object-orientation
- Author
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Marc Scholl and Schek, Hans-Jörg
- Subjects
data models ,object-orientation ,complex objects ,query language ,ddc:004 ,nested relations - Abstract
Complex Object models, semantic or knowledge representation models on the one side, and object-oriented models on the other side are currently considered candidates for future databases. Either of them have their particular strongpoints and weaknesses, such that up to now no single model could be identified to suit all needs. Database models provide limited structuring capabilities and too poor semantics and object-oriented approaches suffer from their navigational one-object-at-a-time style of operation, that is, they need set oriented "object algebra" operations. In this paper we show how the approaches can be mixed into a single coherent approach, in an evolutionary way preserving their respective advantages: flexibility through powerful structuring primitives, rich semantics, encapsulation, and efficiency through optimizable descriptive, set-oriented query and update languages.
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