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60
Parallel database systems: the future of high performance database systems
- COMMUNICATIONS OF THE ACM
, 1992
"... Parallel database machine architectures have evolved from the use of exotic hardware to a software parallel dataflow architecture based on conventional shared-nothing hardware. These new designs provide impressive speedup and scaleup when processing relational database queries. This paper reviews t ..."
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Cited by 641 (13 self)
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Parallel database machine architectures have evolved from the use of exotic hardware to a software parallel dataflow architecture based on conventional shared-nothing hardware. These new designs provide impressive speedup and scaleup when processing relational database queries. This paper reviews the techniques used by such systems, and surveys current commercial and research systems.
Parallel Database Systems: The Future of Database Processing or a Passing Fad?
- SIGMOD RECORD
, 1991
"... Parallel database machine architectures have evolved from the use of exotic hardware to a software parallel dataflow architecture based on conventional shared-nothing hardware. These new designs provide impressive speedup and scaleup when processing relational database queries. This paper reviews th ..."
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Cited by 53 (7 self)
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Parallel database machine architectures have evolved from the use of exotic hardware to a software parallel dataflow architecture based on conventional shared-nothing hardware. These new designs provide impressive speedup and scaleup when processing relational database queries. This paper reviews the techniques used by such systems, and surveys current commercial and research systems.
On the Complexity of Nonrecursive XQuery and Functional Query Languages on Complex Values
- In Proc. PODS’05
"... This article studies the complexity of evaluating functional query languages for complex values such as monad algebra and the recursion-free fragment of XQuery. We show that monad algebra with equality restricted to atomic values is complete for the class TA[2O(n) , O(n)] of problems solvable in lin ..."
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Cited by 47 (2 self)
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This article studies the complexity of evaluating functional query languages for complex values such as monad algebra and the recursion-free fragment of XQuery. We show that monad algebra with equality restricted to atomic values is complete for the class TA[2O(n) , O(n)] of problems solvable in linear exponential time with a linear number of alternations. The monotone fragment of monad algebra with atomic value equality but without negation is complete for nondeterministic exponential time. For monad algebra with deep equality, we establish TA[2O(n) , O(n)] lower and exponential-space upper bounds. We also study a fragment of XQuery, Core XQuery, that seems to incorporate all the features of a query language on complex values that are traditionally deemed essential. A close connection between monad algebra on lists and Core XQuery (with “child ” as the only axis) is exhibited, and it is shown that these languages are expressively equivalent up to representation issues. We show that Core XQuery is just as hard as monad algebra w.r.t. query and combined complexity, and that it is in TC0 if the query is assumed fixed. As Core XQuery is NEXPTIME-hard, it is commonly believed that any algorithm for evaluating Core XQuery has to require exponential amounts of working memory and doubly exponential time in the worst case. We present a property of queries – the lack of a certain form of composition – that virtually all real-world XQueries have and that allows for query evaluation in singly exponential time and polynomial space. Still, we are able to show for an important special case – Core XQuery with equality testing restricted to atomic values – that the composition-free language is just as expressive as the language with composition. Thus, under widely-held complexitytheoretic assumptions, the composition-free language is an exponentially less succinct version of the language with composition.
A Conceptual Modelling Formalism for Temporal Database Applications
- Information Systems
, 1991
"... Arguably the most critical of all activities in the development of an information system is that of requirements modelling. The effectiveness of such a specification depends largely on the ability of the chosen conceptual model to represent the problem domain in such a way so as to permit natural an ..."
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Cited by 43 (3 self)
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Arguably the most critical of all activities in the development of an information system is that of requirements modelling. The effectiveness of such a specification depends largely on the ability of the chosen conceptual model to represent the problem domain in such a way so as to permit natural and rigorous descriptions within a methodological framework. Recent years have witnessed an increased demand for information systems which cover a wide spectrum of application domains. This, inevitably, has had the effect of demanding conceptual models of enhanced functionality and expressive power than is currently possible in practice. This paper introduces the TEMPORA modelling paradigm for developing information system applications from a unified perspective which deals with definitional, intentional and constrain knowledge. The paper discusses in detail one of the components of the TEMPORA conceptual model, the Entity-Relationship-Time (ERT) model, which deals with structural aspects in...
Ontology based Business Process Description
- In: Proceedings of the CAiSE´05 WORKSHOPS
, 2005
"... Abstract. Coupling of cross-organizational business processes in electronic markets is a difficult and time-consuming task. In practice business processes are geographically distributed which makes it particulary difficult for business partners to coordinate their supply chains and customer relation ..."
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Cited by 27 (4 self)
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Abstract. Coupling of cross-organizational business processes in electronic markets is a difficult and time-consuming task. In practice business processes are geographically distributed which makes it particulary difficult for business partners to coordinate their supply chains and customer relationship management with business units. By using formal description languages such as Petri nets for modeling inter-organizational business processes, purely syntactic composition problems of distributed business environments can be solved. However, the missing semantic representation of Petri nets can hamper the interconnectivity of business processes. Usually, several business partners, even if they share similar demands, have their own specific vocabularies. By representing business processes with Petri nets in combination with the Web Ontology Language (OWL) our approach provides flexibility, ease of integration and a significant level of automation of loosely coupled business processes even if they do not share their respective vocabularies. 1
The Time Dimension in Conceptual Modelling
, 1991
"... In recent years there has been a growing interest in the explicit introduction of time modelling in a conceptual schema. This has come about as as a result of the relaisation that realisation that the development of large information systems is becoming increasingly more difficult as user requiremen ..."
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Cited by 26 (0 self)
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In recent years there has been a growing interest in the explicit introduction of time modelling in a conceptual schema. This has come about as as a result of the relaisation that realisation that the development of large information systems is becoming increasingly more difficult as user requirements become broader and more sophisticated. Arguably the most critical activity in the development of a large data-intensive information system is that of requirements capture and specification. The effectiveness of such a specification depends largely on the ability of the chosen conceptual model to represent the problem domain in such a way so as to permit natural and rigorous descriptions within a methodological framework. The explicit representation of time in a conceptual model plays a major role in achieving this effectiveness. This paper examines the ontology and properties of time in the context of information systems and conceptual modelling. In particular, a critical set of ontologic...
A Cost-Space Approach to Distributed Query Optimization in Stream Based Overlays
- In Proc. IEEE International Workshop on Networking Meets Databases (NetDB ’05
, 2005
"... Abstract — Distributed stream-based applications, such as continuous query systems, have network scale and time characteristics that challenge traditional distributed query optimization. The optimization sub-problems of plan generation and service placement should be integrated to meet these challen ..."
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Cited by 12 (3 self)
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Abstract — Distributed stream-based applications, such as continuous query systems, have network scale and time characteristics that challenge traditional distributed query optimization. The optimization sub-problems of plan generation and service placement should be integrated to meet these challenges. These tasks have typically been treated as independent sub-problems because of the complexity of their integration. We suggest cost spaces as one way to mitigate this complexity. We further consider how cost spaces can be used to allow tractable multi-query optimization. I.
DLFM: A transactional resource manager
- In Proc. of the 2000 ACM SIGMOD Intl. Conference on Management of Data
, 2000
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An overview of nonprocedural languages
- In Proceedings ofa Symposium on Very High Level Languages. ACM-SIGPLAN
, 1974
"... This paper attempts to describe some of the basic characteristics and issues involving the class of programming languages commonly referred to as "nonprocedural " or "very high level". The paper discusses major issues such as terminology, rela-tiveness, and arbitrary sequencing. ..."
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Cited by 6 (0 self)
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This paper attempts to describe some of the basic characteristics and issues involving the class of programming languages commonly referred to as "nonprocedural " or "very high level". The paper discusses major issues such as terminology, rela-tiveness, and arbitrary sequencing. Five features of nonprocedural languages are described, and a number of specific languages are discussed brief-ly. A short history of the subject is included. I t is characteristic of the programming f ie ld that much time and energy has been, and wi l l con-tinue to be, spent on terminology. This is per-haps an indication of the youth as well as the
Information Modeling and Higher-Order Types
- Riga Tech. University
, 2004
"... Abstract: While some information modeling approaches (e.g. the Relational Model, and Object-Role Modeling) are typically formalized using first-order logic, other approaches to information modeling include support for higher-order types. There appear to be three main reasons for requiring higher-ord ..."
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Cited by 4 (1 self)
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Abstract: While some information modeling approaches (e.g. the Relational Model, and Object-Role Modeling) are typically formalized using first-order logic, other approaches to information modeling include support for higher-order types. There appear to be three main reasons for requiring higher-order types: (1) to permit instances of categorization types to be types themselves (e.g. the Unified Modeling Language introduced power types for this purpose); (2) to directly support quantification over sets and general concepts; (3) to specify business rules that cross levels/metalevels (or ignore level distinctions) in the same model. As the move to higher-order logic may add considerable complexity to the task of formalizing and implementing a modeling approach, it is worth investigating whether the same practical modeling objectives can be met while staying within a first-order framework. This paper examines some key issues involved, suggests techniques for retaining a first-order formalization, and also makes some suggestions for adopting a higher-order semantics. 1
