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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    BIT 30 (1990), S. 34-41 
    ISSN: 1572-9125
    Keywords: H.2.1
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract In the relational model of data, Rissanen's Theorem provides the basis for the usual normalization process based on decomposition of relations. However, many difficulties occur if information is incomplete in databases and nulls are required to represent missing or unknown data. We concentrate here on the notion of outer join and find some reasonable conditions to guarantee that outer join will also preserve the lossless join property for two relations. Next we provide a generalization of this result to several relations.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Distributed and parallel databases 8 (2000), S. 7-40 
    ISSN: 1573-7578
    Keywords: information warfare ; trusted recovery ; databases ; security ; malicious transactions ; transaction histories
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract We consider recovery from malicious but committed transactions. Traditional recovery mechanisms do not address this problem, except for complete rollbacks, which undo the work of good transactions as well as malicious ones, and compensating transactions, whose utility depends on application semantics. We develop an algorithm that rewrites execution histories for the purpose of backing out malicious transactions. Good transactions that are affected, directly or indirectly, by malicious transactions complicate the process of backing out undesirable transactions. We show that the prefix of a rewritten history produced by the algorithm serializes exactly the set of unaffected good transactions. The suffix of the rewritten history includes special state information to describe affected good transactions as well as malicious transactions. We describe techniques that can extract additional good transactions from this latter part of a rewritten history. The latter processing saves more good transactions than is possible with a dependency-graph based approach to recovery.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Distributed and parallel databases 8 (2000), S. 399-446 
    ISSN: 1573-7578
    Keywords: database management systems ; transaction processing ; transaction dependencies ; commit protocols ; distributed systems ; multilevel security
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract Numerous extended transaction models have been proposed in the literature to overcome the limitations of the traditional transaction model for advanced applications characterized by their long durations, cooperation between activities and access to multiple databases (like CAD/CAM and office automation). However, most of these extended models have been proposed with specific applications in mind and almost always fail to support applications with slightly different requirements. We propose the Multiform Transaction model to overcome this limitation. The multiform transaction model supports a variety of other extended transaction models. A multiform transaction consists of a set of component transactions together with a set of coordinators which specify the transaction completion dependencies among the component transactions. A set of transaction primitives allow the programmer to define custom completion dependencies. We show how a wide range of extended transactions can be implemented as multiform transactions, including sagas, transactional workflows, nested transactions, and contingent transactions. We allow the programmers to define their own primitives—having very well-defined interfaces—so that application specific transaction models like distributed multilevel secure transactions can also be supported.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    International journal of parallel programming 12 (1983), S. 269-283 
    ISSN: 1573-7640
    Keywords: Entity-relationship diagram ; functional dependency ; fundamental fd ; relational scheme ; regular ERD ; Boyce-Codd normal form ; loop-free ERD
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract In Ref. 8, we introduced a simplifying assumption about entity-relationship diagrams (ERDs), called regularity, and showed that regular ERDs have several desirable properties. One such property is that every relation schema in the ERD's canonical relational scheme can be put into Third Normal Form. We left open there the more basic question: under what conditions would the original relation schemas actually be in Boyce-Codd Normal Form (BCNF)? Since the visible semantics of ERDs determine naturally their associated functional dependencies (fd's), it is important to know when an ERD, as designed, already has this strongest normal form given purely in terms of fd's. We show here a sufficient diagrammatic condition (loop-free) under which a regular ERD will have databases enjoying the benefits of BCNF.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Annals of mathematics and artificial intelligence 22 (1998), S. 29-58 
    ISSN: 1573-7470
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract This paper presents a general framework to define time granularity systems. We identify the main dimensions along which different systems can be characterized, and investigate the formal relationships among granularities in these systems. The paper also introduces the notion of a network of temporal constraints with (multiple) granularities emphasizing the semantic and computational differences from constraint networks with a single granularity. Consistency of networks with multiple granularities is shown to beNP‐hard in general and approximate solutions for this problem and for the minimal network problem are proposed.
    Type of Medium: Electronic Resource
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  • 6
    Title: Proceedings of the 1993 ACM SIGMOD International Conference on Management of Data; Vol. 22
    Contributer: Bunemann, Peter , Jajodia, Sushil , ACM , ACM / SIGMOD
    Publisher: New York, NY :ACM,
    Year of publication: 1993
    Pages: 565 S.
    Series Statement: SIGMOD Record Vol. 22
    Type of Medium: Book
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