Join dependencies can be divided into cyclic and acyclic join dependencies. A fundamental result in dependency theory is that a join dependency is acyclic if and only if it is equivalent to a set of MVDs. In addition to this characterization it has been shown that such a set of MVDs has...
multivalued dependencyjoin dependencythird normal formfourth normal formfifth normal formthe entity-relationship approachIn this paper, we show that multivalued dependencies and join dependencies are not very viable for certain cases of relational database design; they are sometimes difficult to be ...
A multivalued dependency X Y is a special case of a join dependency expressed as [ XY , X ( U XY )], which specifies that the decomposition of any instance I satisfying [ XY , X ( U XY )] into π XY ( I ) and π X ( U XY ) ( I ) is lossless, i.e., I = π XY ...
One of them is defined as a set including an acyclic joint dependency and a set of functional dependencies such that the left and right sides of each functional dependency are included in one of the attribute sets that construct the acyclic join dependency. (2) For a relation scheme with an...
the value of attributes inYis independent of the value of attributes inZ. A multivalued dependencyX↠Yis a special case of ajoin dependencyexpressed as ⋈[XY,X(U−XY)], which specifies that the decomposition of any instanceIsatisfying ⋈ [XY,X(U−XY)] into πXY(I) and πX(U...
Multivalued dependencyrelational databasefuzzy functionIn this paper we discuss an important integrity constraint called multivalued dependency (mvd), which occurs as a result of the first normal form, in the framework of a newly proposed model called fuzzy multivalued relational data model. The ...
functional dependencymultivalued dependency(MVD) 规范化函数依赖多值依赖多值依赖冗余模式算法DependencyModeThe normalization problem of XML was studied, which should avoid the occurrence of redundant information in documents. First the paper gave the definition of functional dependencies and path for XML, ...
We describe an algorithm to test whether a multivalued dependency is implied by a set of functional and join dependencies. The worst case running time of the algorithm is O ( nm ), where n is the length of the input and m is the number of the attributes in the universe. We also ...
Multivalued dependencyjoin dependencyacyclic database schemasconflict-freedomNathan Goodman and Y.C. TayInformation Processing LettersN. Goodman and Y. C. Tay. A characterization of multivalued dependencies equiv- alent to a join dependency. Inf. Process. Lett., 18(5):261-266, 1984....
In [8] Goodman and Tay have proposed an approach based on the possible equivalence of M to a single (acyclic) join dependency (JD). We remark that their characterization does not lend an insight into the nature of such sets of MVDs. Here, we use notions that are intrinsic to MVDs to...