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1996
We givea straightforward definition for redundancy in individual nested relations and define a new normal form that precisely characterizes redundancy for nested relations. We base our definition of redundancy on an arbitrary set of functional and multivalued dependencies, and show that our definition of nested normal form generalizes standard relational normalization theory. In addition, we give a condition that can prevent an unwanted structural anomaly in nested relations, namely, embedded nested relations with at most one tuple, Like other normal forms, our nested normal form can serve as a guide for database design.
ACM Transactions on Database Systems, 1996
We givea straightforward definition for redundancy in individual nested relations and define a new normal form that precisely characterizes redundancy for nested relations. We base our definition of redundancy on an arbitrary set of functional and multivalued dependencies, and show that our definition of nested normal form generalizes standard relational normalization theory. In addition, we give a condition that can prevent an unwanted structural anomaly in nested relations, namely, embedded nested relations with at most one tuple, Like other normal forms, our nested normal form can serve as a guide for database design.
Programming and Computer Software, 2002
ACM Transactions on Database Systems, 1992
A key is simple if it consists of a single attribute.
ACM Transactions on Database Systems, 1987
We consider nested relations whose schemes are structured as trees, called scheme trees, and introduce a normal form for such relations, called the nested normal form. Given a set of attributes U, and a set of multivalued dependencies (MVD´s) M over these attributes, we present an algorithm to obtain a nested normal form decomposition of U with respect to M. Such a decomposition has several desirable properties, such as explicitly representing a set of full and embedded MVD´s implied by M, and being a faithful and nonredundant representation of U. Moreover, if the given set of MVD´s is conflict free, then the nested normal form decomposition is also dependency preserving. Finally, we show that if M is conflict free, then the set of root-to-leaf paths of scheme trees in nested normal form decomposition is precisely the unique 4NF decomposition [Fa, L2] of U with respect to M. Recently, several researchers have reported query languages for non-first normal form relational databases. Jaeschke and Schek [JS] extended relational algebra by nest and unnest operators over single attributes to obtain nested relations from normalized relations and vice versa. Fischer and Thomas [FT] study operators for non-first normal form relations in a more general setting. Abiteboul and Bideout [AB] describe the use of non-first normal form relations in the VERSO machine [Ba], and give algebraic operators and their properties. Ozsoyoglu and Ozsoyoglu [OO] consider operators similar to that of [JS], for set valued relations (i.e., relations with at most one level of __________________ *
ACM Transactions on Database Systems, 1981
A new normal form for relational databases, called domain-key normal form (DK/NF), is defined. Also, formal definitions of insertion anomaly and deletion anomaly are presented. It is shown that a schema is in DK/NF if and only if it has no insertion or deletion anomalies. Unlike previously defined normal forms, DK/NF is not defined in terms of traditional dependencies (functional, multivalued, or join). Instead, it is defined in terms of the more primitive concepts of domain and key, along with the general concept of a "constraint."
When an attempt is made to modify tables that have not been sufficiently normalized undesirable sideeffects may follow. This can be further specified as an update, insertion or deletion anomaly depending on whether the action that causes the error is a row update, insertion or deletion respectively. If a relation R has more than one key, each key is referred to as a candidate key of R. Most of the practical recent works on database normalization use a restricted definition of normal forms where only the primary key (an arbitrary chosen key) is taken into account and ignoring the rest of candidate keys. In this paper, we propose an algorithmic approach for database normalization up to third normal form by taking into account all candidate keys, including the primary key. The effectiveness of the proposed approach is evaluated on many real world examples.
This paper develops the database design methodology proposed in [19] which is based on the graphical representation of dependencies among database attributes. Rooted in the papers of Bernstein, Smith, Mannila and Raiha, Ausiello, D'Atri and Sacca, the methodology lacks the formalistic bedrock so abundant in normalization papers. It is intentionally less rigorous but more relevant to the database designers. Some issues presented in [19] are deepened: adding new attributes, surrogate keys, and removing symmetric dependencies. Others are completely new, such as: fixing functional dependencies problems using inclusion dependencies, altering the dependencies graph in order to achieve Boyce-Codd Normal Form, and transforming Multi-Valued Dependencies into Functional Dependencies.
International journal of engineering research and technology, 2013
This paper propose an efficient data cleaning by using extended Conditional Functional Dependencies (eCFD’s), which is an extension of Conditional Functional Dependencies(CFD’s). eCFD’s intend to solve the multi-valued inconsistencies to trounce drawbacks of CFD’s which use pattern tableau to hold individual tuples in a table for cleaning relational data by supporting only single valued attributes. SQL techniques are used to create patterns of semantically related values for detecting single tuple CFD violations. By introducing a query and an algorithm we provide better competence for eliminating data redundancy in multi-valued attributes using nested relational database. We experimentally analyze the efficiency and performance of these eCFD based techniques in improving data quality and displays the tentative results graphically.
Proceedings of the International …, 2003
Object-Relational Data Model (ORM) has included various Object-Oriented (OO) conceptual implementations in a relational environment. One of the advances is the inclusion of ROW type feature to facilitate nested relation structure. In this paper, we propose a new ...
FoIKS, 2020
Classical normalisation theory has a number of lacunas although it is commonly and widely accepted and it is the basis for database theory since the 80ies. Most textbooks and monographs still follow this approach despite the good number of open problems. Today, modern object-relational DBMS offer far better capabilities than the systems that have been built in the past based on the strict relational paradigm. Constraint maintenance has been oriented on transformation of structures to structures that are free of functional dependencies beside key constraints. The maintenance of coherence constraints such as two-type inclusion constraints has been neglected although this maintenance might be the most expensive one. In reality normalisation is local optimisation that exclusively considers functional dependency maintenance. We thus need a different normalisation approach. This paper develops an approach towards optimisation of schemata and global normalisation. This approach results in a denormalisation and object-relational database schemata. 1 Normalisation-The Good, The Bad, The Ugly Normalisation is considered to be one of the pearls of database theory. There is almost no database course that does not teach this part of a theory. The main results have been achieved during the 70ies, 80ies and early 90ies. Since then the theory is considered to be completed although new DBMS (database management systems) and new database paradigms have been developed since then. There are very few publications on object-relational structures. XML approaches have mainly be following this research paradigm.
Zenodo (CERN European Organization for Nuclear Research), 2010
We initiate in this work the study of a sort of redundancy problem revealed by what we call redundant relations. Roughly, we define a redundant relation in a database instance (dbi) as a k-ary relation R such that there is a first-order query which evaluated in the reduced dbi, (i.e., the dbi without the redundant relation R) gives us R. So, given that first-order types are isomorphism types on finite structures, we can eliminate that relation R as long as the equivalence classes of the relation of equality of the first-order types for all k-tuples in the dbi are not altered. It turns out that in a fixed dbi, the problem of deciding whether a given relation in the dbi is redundant is decidable, though intractable, as well as the problem of deciding whether there is any relation symbol in the schema which is a redundant relation in the given dbi. We then study redundant relations with a restricted notion of equivalence so that the problem becomes tractable.
Journal of Database Management, 2002
This paper discusses normalization of relations when the candidate keys of a relation have missing information represented by nulls. The paper shows that when the missing information is of the type “not applicable” or “does not exist,” problems and confusion can arise in normalizing relations. Candidate keys with missing information commonly are found in relations that represent information on two entities with a one-to-one relationship between them. The current definition of Boyce-Codd Normal Form (BCNF) is ineffective in identifying poor designs in such relations that may have insertion/deletion anomalies. It is shown that the above problem can be corrected by incorporating the concept of entity integrity rule into the definition of BCNF. This paper also shows that incorporating the entity integrity rule into the definition of either a relation or a candidate key does not provide a satisfactory solution to the problem.
2011
Thenormalizationis a practiceused to design the relation (s)for agood databaseeliminating undesirablefunctional dependencies am ongst that exist amongst attributes oftherelation.The complexities involved in the normalization of relations, have mowed down vendors from automating the n ormalization processes. Althoughthe keywordnormalizationisexisting indata manipulation l anguageofStructuredQuery Language (SQL)standard This paperunravels the complexities involved in the normalization process and proposes an automatic methodologyfor refining the relations with normalization.The primary key for each re lation is designe d based on thesuperset ofminimum attribute(s), whichuniquely determines other attribute values of the tuple in the relation. Utilizing the blend of analytical and synthetic approaches, the proposedimplementation processforms and refines the relationsgrouping (with the use of axioms) the desirable functional dependencies of the relation to satisfy the first, second and t...
Lecture Notes in Computer Science, 2012
In the relational model of data the Fourth Normal Form condition guarantees the elimination of data redundancy in terms of functional and multivalued dependencies. For efficient means of data processing the industry standard SQL permits partial data and duplicate rows of data to occur in database systems. Here, the combined class of uniqueness constraints, functional and multivalued dependencies is more expressive than the class of functional and multivalued dependencies itself. Consequently, the Fourth Normal Form condition is not suitable for SQL databases. We characterize the associated implication problem of the combined class in the presence of NOT NULL constraints axiomatically, algorithmically and logically. Based on these results we are able to establish a suitable Fourth Normal Form condition for SQL.
International Journal of Database Management Systems, 2011
In this paper a tool called RDBNorma is proposed, that uses a novel approach to represent a relational database schema and its functional dependencies in computer memory using only one linked list and used for semi-automating the process of relational database schema normalization up to third normal form. This paper addresses all the issues of representing a relational schema along with its functional dependencies using one linked list along with the algorithms to convert a relation into second and third normal form by using above representation. We have compared performance of RDBNorma with existing tool called Micro using standard relational schemas collected from various resources. It is observed that proposed tool is at least 2.89 times faster than the Micro and requires around half of the space than Micro to represent a relation. Comparison is done by entering all the attributes and functional dependencies holds on a relation in the same order and implementing both the tools in same language and on same machine.
Proceedings of the Thirtieth Australasian Conference on Computer Science Volume 62, 2007
A common approach in designing relational databases is to start with a universal relation schema, which is then decomposed into multiple subschemas. A good choice of subschemas can be determined using integrity constraints defined on the schema, such as functional, multivalued or join dependencies.
Information Sciences, 1992
We consider the problem of unifying functional dependencies (FDs) and multivalued dependencies (MVDS) in designing relational database schemes. Given a set D of dependencies (MVDs and FDs) over a universal scheme Li, we define a different set of MVDs over U, called the envelope set for D, so that a database scheme with respect to D can be designed by considering only the MVDs in the envelope set for D, instead of treating MVDs and FDs in D separately. We show that a database scheme is in 4NF with respect to D (BCNF when D has only FDs) if it is 4NF with respect to the envelope set for D. By utilizing the envelope set of dependencies we extend the conflict free property of sets of MVDs to apply to sets of FDs and MVDs. We show that if a set D of dependencies is extended conflict-free, then there exists an acyclic, joint lossless 4NF decomposition (BCNF) with respect to D which is also dependency preserving. Except for the case where D is a set of MVDs only, this was an open problem in the literature. We also show that, for a set M of MVDs, an acyclic join lossless 4NF decomposition exists if M does not split its keys. Given a set of dependencies D, obtaining the envelope set for D, determining whether D is extended conflict free, and if D is extended conflict free, then obtaining a dependency preserving, acyclic, join lossless, 4NF decomposition can be done in time polynomial in the size of D. *This research is supported by the NSF under Grants No. 8306616 and No. 8605554 and an IBM Faculty Development Award.
Lecture Notes in Computer Science, 2011
In the relational model of data the Boyce-Codd-Heath normal form, commonly just known as Boyce-Codd normal form, guarantees the elimination of data redundancy in terms of functional dependencies. For efficient means of data processing the industry standard SQL permits partial data and duplicate rows of data to occur in database systems. Consequently, the combined class of uniqueness constraints and functional dependencies is more expressive than the class of functional dependencies itself. Hence, the Boyce-Codd-Heath normal form is not suitable for SQL databases. We characterize the associated implication problem of the combined class in the presence of NOT NULL constraints axiomatically, algorithmically and logically. Based on these results we are able to establish a suitable normal form for SQL.
Acta Cybernetica
PREFACE "It will be seen that logic can be used as a programming language, as a query language, to perform deductive searches, to maintain the integrity of data bases, to provide a formalism for handling negative information, to generalize concepts in knowledge representation, and to represent and manipulate data structures. Thus, logic provides a powerful tool for databases that is accomplished by no other approach developed to data. It provides a unifying mathematical theory for data bases." H. Gallaire, J. Minker April 1978 Today, database is a fascinating word. Commercial database management systems have been available for two decades, at the beginning in the form of hierarchical and network models. Two opposing research trends in database were created in the early -E (mployees) Address -Salary -D (epartments) Name -D (epartments) N (umbe) r -A (rticles) Name -M (arket) N (umbe) r (of the article) -M (arket) Price -Quantity -S (uppliers) Name -S (uppliers) Address -S (uppliers) N (umbe) r -S (uppliers) Price . The corresponding domains are obvious by the names and therefore omitted. Given now the following entity schemes Employees = ({EmpNr, EName, EAddress, Salary}, {EmpNr}), Department = ({DName, DNr}, {DNr}), Article = ({AName, MNr, MPrice, Quantity}, {MNr}), Supplier = ({SName, SAddress}, {SName, SAddress}).
Journal of Computer and System Sciences, 1985
Nesting is a way of transforming a tirst-normal-form relation into a structure with setvalued entries in some positions instead of atomic entries. In this paper we study how functional and multivalued dependencies interact with nesting. We describe how nesting preserves, alters, or destroys dependencies holding in a tirst-normal-form relation. We then consider dependencies which hold in each block of the horizontally decomposed relation induced by nesting and study the relationship between these "local" dependencies and "global" dependencies in the normalized relation. 0 1985 Academic PESS, IX.
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