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Knowledge and Data Engineering, IEEE Transactions on

Issue 3 • Date Jun 1996

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Displaying Results 1 - 13 of 13
  • A trie compaction algorithm for a large set of keys

    Page(s): 476 - 491
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1364 KB)  

    A trie structure is frequently used for various applications, such as natural language dictionaries, database systems and compilers. However, the total number of states of a trie (and transitions between them) becomes large, so that the space cost may not be acceptable for a huge key set. In order to resolve this disadvantage, this paper presents a new scheme, called a “two-trie”, that enables us to perform efficient retrievals, insertions and deletions for the key sets. The essential idea is to construct two tries for both front and rear compressions of keys, which is similar to a DAWG (directed acyclic word-graph). The approach differs from a DAWG in that the two-trie approach presented can uniquely determine information corresponding to keys while a DAWG cannot. For an efficient implementation of the two-trie, two types of data structures are introduced. Theoretical and experimental observations show that the method presented is more practical than existing ones considering the use of dynamic key sets, information storage of keys and compression of transitions View full abstract»

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  • A graph-based framework for multiparadigmatic visual access to databases

    Page(s): 455 - 475
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    Describes an approach for multiparadigmatic visual access integration of different interaction paradigms. The user is provided with an adaptive interface augmented by a user model, supporting different visual representations of both data and queries. The visual representations are characterized on the basis of the chosen visual formalisms, namely forms, diagrams and icons. To access different databases, a unified data model called the “graph model” is used as a common underlying formalism to which databases, expressed in the most popular data models, can be mapped. Graph model databases are queried through the adaptive interface. The semantics of the query operations is formally defined in terms of graphical primitives. Such a formal approach permits us to define the concept of an “atomic query”, which is the minimal portion of a query that can be transferred from one interaction paradigm to another and processed by the system. Since certain interaction modalities and visual representations are more suitable for certain user classes, the system can suggest to the user the most appropriate interaction modality as well as the visual representation, according to the user model. Some results on user model construction are presented View full abstract»

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  • Testing expert systems in process control

    Page(s): 403 - 415
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    Special features of process control expert systems (PCX) make it both necessary and feasible to test them in a comprehensive manner. FAITH, an automated regression testing environment for PCX, integrates five specially adapted testing techniques, exploiting external specifications gained from the process control environment. FAITH also offers a set of metrics which can be used to predict testability during the early phases of PCX development. FAITH has been developed for a major German chemicals company where it is routinely used for certifying PCX, and for guiding design-for-testability View full abstract»

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  • Principles for organizing semantic relations in large knowledge bases

    Page(s): 492 - 496
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    Defines principles for organizing semantic relations represented by slots in frame-structured knowledge bases. We organize slots based on the knowledge-level semantics of relations and the symbol-level function of slots that implement the representation language. The symbol-level organization of slots depends on the inferencing and expressive capabilities of the knowledge representation system. At the knowledge level, two entirely different organizational schemes are identified: one based on linguistic similarities and differences, and another based on the types of concepts being related View full abstract»

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  • An optimal resource scheduler for continuous display of structured video objects

    Page(s): 508 - 511
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (392 KB)  

    A structured video consists of a collection of background objects, characters, spatial and temporal constructs, and rendering features. Assuming a platform consisting of a fixed amount of memory and a magnetic disk drive, this study presents a resource scheduler for the continuous display of structured video that minimizes both the latency observed by a display and its required amount of memory View full abstract»

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  • Objective-driven monitoring for broadband networks

    Page(s): 391 - 402
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    An approach to sensor configuration, installation, and activation for real-time monitoring of broadband networks for performance management is presented. An objective-driven measurement strategy for establishing the dynamic and statistical databases of the network is described. Objective driven monitoring allows the activation of sensors for data collection and abstraction based on a set of objectives. The objectives are derived from the quality of service requirements for real-time traffic control and operator submitted queries. The methodology of objective-driven monitoring for selective activation of sensors is implemented as a set of rules in the knowledge base of the monitor View full abstract»

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  • Towards the correctness and consistency of update semantics in semantic database schema

    Page(s): 503 - 507
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    Discusses a paradigm and prototype system for the design-time expression, checking and automatic implementation of the semantics of database updates. Enforcement rules are viewed as the implementation of constraints and are specified, checked for consistency, and then finally mapped to object-oriented code during database design. A classification of enforcement rule types is provided as a basis for these design activities, and the general strategy for specification, analysis and implementation of these rules within a semantic modeling paradigm is discussed. SORAC (Semantics, Objects, Relationships And Constraints), a prototype database design system of the University of Rhode Island, is also described View full abstract»

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  • A deductive object-oriented database system for situated inference in law

    Page(s): 496 - 503
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    Deductive object-oriented databases and situation theory are two important areas of research in the fields of databases and of linguistics. “AI and law” is a new field attracting both AI researchers and legal practitioners. Our research brings together the former two fields with the aim of designing knowledge applications in the latter. This is achieved through a formal model for legal reasoning, 𝒮ℳ (“Situation-theoretic Model”), and a deductive object-oriented database system, 𝒬𝒰ℐ𝒳𝒪𝒯ℰ. The purpose of this paper is to introduce the key features of this formal model, based on situation theory, and to describe how this database system can implement this abstract model for complex legal reasoning applications. Concrete examples from legal precedents are used to illustrate these advanced features View full abstract»

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  • Optimization of parallel execution for multi-join queries

    Page(s): 416 - 428
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    We study the subject of exploiting interoperator parallelism to optimize the execution of multi-join queries. Specifically, we focus on two major issues: (1) scheduling the execution sequence of multiple joins within a query, and (2) determining the number of processors to be allocated for the execution of each join operation obtained in (1). For the first issue, we propose and evaluate by simulation several methods to determine the general join sequences, or bushy trees. Despite their simplicity, the heuristics proposed can lead to the general join sequences that significantly outperform the optimal sequential join sequence. The quality of the join sequences obtained by the proposed heuristics is shown to be fairly close to that of the optimal one. For the second issue, it is shown that the processor allocation for exploiting interoperator parallelism is subject to more constraints-such as execution dependency and system fragmentation-than those in the study of intraoperator parallelism for a single join. The concept of synchronous execution time is proposed to alleviate these constraints. Several heuristics to deal with the processor allocation, categorized by bottom-up and top-down approaches, are derived and are evaluated by simulation. The relationship between issues (1) and (2) is explored. Among all the schemes evaluated, the two-step approach proposed, which first applies the join sequence heuristic to build a bushy tree as if under a single processor system, and then, in light of the concept of synchronous execution time, allocates processors to execute each join in the bushy tree in a top-down manner, emerges as the best solution to minimize the query execution time View full abstract»

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  • Intelligent query answering by knowledge discovery techniques

    Page(s): 373 - 390
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    Knowledge discovery facilitates querying database knowledge and intelligent query answering in database systems. We investigate the application of discovered knowledge, concept hierarchies, and knowledge discovery tools for intelligent query answering in database systems. A knowledge-rich data model is constructed to incorporate discovered knowledge and knowledge discovery tools. Queries are classified into data queries and knowledge queries. Both types of queries can be answered directly by simple retrieval or intelligently by analyzing the intent of query and providing generalized, neighborhood or associated information using stored or discovered knowledge. Techniques have been developed for intelligent query answering using discovered knowledge and/or knowledge discovery tools, which includes generalization, data summarization, concept clustering, rule discovery, query rewriting, deduction, lazy evaluation, application of multiple-layered databases, etc. Our study shows that knowledge discovery substantially broadens the spectrum of intelligent query answering and may have deep implications on query answering in data- and knowledge-base systems View full abstract»

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  • Path signatures: a way to speed up recursion in relational databases

    Page(s): 446 - 454
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    Composite objects often involve recursive relationships, so-called bills-of-materials, which are cumbersome to handle in relational database systems. The relationships constitute a directed graph, where the successors of a node represent its components, recursively. Instead of the whole transitive closure (all ancestor-descendant pairs), the task is to retrieve the descendants of any given node. A simple relational solution is suggested, which packs information of the ancestor path of each node into a fixed-length code, called the signature. The code is nonunique, and its purpose is to define a relatively small superset of the descendants, as well as to establish a basis for clustering. It supports effective retrieval of the descendants, in terms of both disk accesses and DBMS calls. The method performs best for tree-structured graphs, where the processing time typically decreases by a factor of more than 10, compared to a simple loop of joins. Also, general directed graphs, both acyclic and cyclic, can be processed more effectively. The method is implemented on top of a relational system, but advantages can be gained on other platforms, too View full abstract»

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  • Current approaches to handling imperfect information in data and knowledge bases

    Page(s): 353 - 372
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    This paper surveys methods for representing and reasoning with imperfect information. It opens with an attempt to classify the different types of imperfection that may pervade data, and a discussion of the sources of such imperfections. The classification is then used as a framework for considering work that explicitly concerns the representation of imperfect information, and related work on how imperfect information may be used as a basis for reasoning. The work that is surveyed is drawn from both the field of databases and the field of artificial intelligence. Both of these areas have long been concerned with the problems caused by imperfect information, and this paper stresses the relationships between the approaches developed in each View full abstract»

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  • Parallel optimization of large join queries with set operators and aggregates in a parallel environment supporting pipeline

    Page(s): 429 - 445
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    Proposes a parallel optimizer for queries containing a large number of joins, as well as set operators and aggregate functions. The platform for the execution is a shared-disk multiprocessor machine supporting bushy parallelism and pipeline processing. Our model partitions the query into almost independent subtrees that can be optimized simultaneously, and it applies an enhanced variation of the iterative improvement technique on those subtrees which contain a large number of joins; this technique is parallelized, too. In order to estimate the cost of the states constructed during the optimization of join subtrees, cost formulae are developed that estimate the cost of relational algebra operators when executed across coalescing pipes View full abstract»

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Aims & Scope

IEEE Transactions on Knowledge and Data Engineering (TKDE) informs researchers, developers, managers, strategic planners, users, and others interested in state-of-the-art and state-of-the-practice activities in the knowledge and data engineering area.

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Meet Our Editors

Editor-in-Chief
Jian Pei
Simon Fraser University