On the operations over relations in the relational model data with two types of null values.

Pavlović, Gordana M.

Displaying similar documents to “On the operations over relations in the relational model data with two types of null values.”

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Rudolf Berghammer, Gunther Schmidt (1993)

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Formal Specification of Relational Model of Data in Z-Notation Формална спецификация на релационния модел на данни в Z-нотация

Dimitrov, Vladimir (2010)

Union of Bulgarian Mathematicians

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Владимир Димитров - Целта на настоящия доклад е формалната спецификация на релационния модел на данни. Тази спецификация след това може да бъде разширена към Обектно-релационния модел на данни и към Потоците от данни. The aim of this paper is to specify formally the Relational Model of Data. This specification could be extended to cover Object-Relational Model of Data and Data Streams. *2000 Mathematics Subject Classification: 68U35. This work was sponsored by...

An XML-algebra for Efficient Set-at-a-time Execution

Maxim Lukichev, Boris Novikov, Pankaj Mehra (2012)

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Repetitions and permutations of columns in the semijoin algebra

Dirk Leinders, Jan Van Den Bussche (2009)

RAIRO - Theoretical Informatics and Applications - Informatique Théorique et Applications

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Codd defined the relational algebra [E.F. Codd, Communications of the ACM 13 (1970) 377–387; E.F. Codd, Relational completeness of data base sublanguages, in Data Base Systems, R. Rustin, Ed., Prentice-Hall (1972) 65–98] as the algebra with operations projection, join, restriction, union and difference. His projection operator can drop, permute and repeat columns of a relation. This permuting and repeating of columns does not really add expressive power to the relational algebra. Indeed,...

Visual representation of formal software specification.

Bogdan, Crenguţa (2002)

Analele Ştiinţifice ale Universităţii “Ovidius" Constanţa. Seria: Matematică

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Pavlović-Lažetić, Gordana, Nenadić, Goran (1995)

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Remarks on symmetrical operations

Kazimierz Urbanik (1966)

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A coalgebraic semantics of subtyping

Erik Poll (2001)

RAIRO - Theoretical Informatics and Applications - Informatique Théorique et Applications

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Coalgebras have been proposed as formal basis for the semantics of objects in the sense of object-oriented programming. This paper shows that this semantics provides a smooth interpretation for subtyping, a central notion in object-oriented programming. We show that different characterisations of behavioural subtyping found in the literature can conveniently be expressed in coalgebraic terms. We also investigate the subtle difference between behavioural subtyping and refinement. ...