NF-NR: A practical normal form for nested relations

Ling, Tok Wang; Yan, Limei

doi:10.1007/bf01976278

Cited by 17 publications

(14 citation statements)

References 11 publications

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“…ORA-SS not only reflects the nested of structured data, but also distinguish between objects, relationships and attributes. The definitions of a normal form ORA-SS schema diagram give the necessary and sufficient conditions for ensuring the corresponding set of nested relations in normal form for set of nested relations [23,24]. (d) XER Extensible Entity Relationship Modeling (XER) model [6], a conceptual modeling approach that can describe XML document structures in a simple visual form reminiscent of the ER model, and has the capability to automatically generate XML document type definitions and schema from such structures.…”

Section: Related Models Summarymentioning

confidence: 99%

Evaluations of Conceptual Models for Semi-structured Database System

Ganguly¹,

Sarkar²

2012

IJCA

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In the latest years many different models for semi structured data have been proposed; most of them, however, are too specific to allow immediate comparison with other models, and do not easily support incremental model design. A number of features which can be considered interesting for a semi structured data model are listed. E.g. we review the more widely used models in Conceptual Modeling for Information Systems (Entity-Relationship and UML), and argue that they do not support effectively modeling of semi structured data. As a consequence, structured and semi structured data cannot be treated in an integrated, holistic way during requirements specification. Research about similarity between semi structured documents (particularly for XML documents) has produced many works in the areas of Database Systems, Artificial Intelligence and Data Mining. In this work introducing a brief survey about it. At first introducing some basic properties. After that, some works are reviewed, highlighting their particularities and general approach. Concluding with a comparison of these works, analyzing their benefits and problems.

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Section: Related Models Summarymentioning

confidence: 99%

Evaluations of Conceptual Models for Semi-structured Database System

Ganguly¹,

Sarkar²

2012

IJCA

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“…The following example is given by Makinouchi (1977) where this type of dependency is shown. In Ling & Yan (1994), the above example is discussed. Two problems are considered.…”

Section: Unnesting and Nesting In Nested Relationsmentioning

confidence: 99%

“…The first one concerns the fact that in this particular example, nested relation 3_POINTS should contain exactly three tuples. The second one is that according to Ling & Yan (1994), the above dependency is difficult to justify, and therefore, the attribute 3_POINTS is better considered as an atomic attribute with a type such as "3 ordered integer pairs" rather than a nested attribute.…”

Section: Unnesting and Nesting In Nested Relationsmentioning

confidence: 99%

Nest and Unnest Operators in Nested Relations

Garani

2008

Data Sci. J.

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By distinguishing nested attributes as Decomposable and Non-Decomposable, it is proved that for all nested relations, unnesting and then renesting on the same attribute yields the original relation subject only to the elimination of duplicate data. Therefore, the statement that was popular in nested relations research: "Unnesting and then nesting on the same attribute of a nested relation does not always yield the original relation" is reconsidered.Keywords: Non-First Normal Form database, Nested relation, Decomposable nested attribute INTRODUCTIONThe Nested or Non-First Normal Form (N1NF) data model was first introduced by Makinouchi (1997), in an effort to relax the first normal form (1NF) assumption, i.e. attributes must contain only atomic values. In contrast, in the N1NF data model, relations are allowed to have both atomic and non-atomic attributes that is the value of an attribute can be a relation itself, which can be considered as a subrelation of the relation. The N1NF data model allows each such subrelation to have relation-valued attributes, thus allowing nesting of relations or embedding of one relation within another. In this paper, relations that contain relation-valued attributes are called nested relations, whereas relations that do not contain relation valued attributes are called flat relations.The N1NF data model has been widely investigated since 1977, as it has offered good solutions for a number of applications, such as engineering design and textual data (Hernández, 1993). The major advantage claimed for nested relations over flat relations is that they minimise data fragmentation (Garani, 2006). The nested structure of the relation makes the semantics of the stored data clear. In addition, redundancy and update anomalies can be minimised and less storage is needed as one relation in non-first normal form can represent many relations in first normal form representation (Gyssens, Suciu & Van Gucht, 2001;Liu, Vincent & Mohania, 1999). As a result, query processing can be faster because a smaller number of join operations may be required (Despande & Larson, 1991).This paper is structured as follows. In Section 2 definitions of nested relations are given and two different categories of nested attributes are distinguished based on the semantics of the data they hold. In Section 3, this distinction is used to demonstrate that unnesting and then nesting on the same attribute of a nested relation R returns the original relation R, subject to the elimination of duplicate tuples. Therefore, the proposition that unnesting a nested relation R and then nesting it on the same attribute does not, necessarily, give the original R relation at all times, which is mentioned in Fischer & Thomas (1983), Jaeschke & Schek (1982), Schek & Scholl (1986) and Thomas & Fischer (1986), is reconsidered. It is shown that this is only a theoretical issue because a case such as that discussed in the earlier papers either cannot exist in the real world or if it does, that no information is lost by unnesting a nes...

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“…Our NF-SS definition and normalization process is similar to that of [7] in concept, but is different in essence, which we have mentioned in the first section.…”

Section: Related Workmentioning

confidence: 99%

“…Normal forms defined for relational databases, either 3NF, BCNF, 4NF and 5NF for the flat relational model, or nested relations like NNF [8] and NF-NR [7], are not directly applicable to semistructured data for the following reasons. First, the semistructured data model is richer and more complex than the flat relational data model.…”

Section: Introductionmentioning

confidence: 99%

NF-SS: A Normal Form for Semistructured Schema

Ling

Lee

et al. 2002

Conceptual Modeling for New Information Systems Technologies

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Abstract. Semistructured data is becoming increasingly important for web applications with the development of XML and related technologies. Designing a "good" semistructured database is crucial to prevent data redundancy, inconsistency and undesirable updating anomalies. However, unlike relational databases, there is no normalization theory to facilitate the design of good semistructured databases. In this paper, we introduce the notion of a semistructured schema and identify the various anomalies that may occur in such a schema. A Normal Form for Semistructured Schemata, NF-SS, is proposed. A semistructured schema in NF-SS guarantees minimal redundancy and hence no undesirable updating anomalies for the associated semistructured databases. Furthermore, a semistructured schema in NF-SS gives a more reasonable representation of real world semantics. We develop an iterative algorithm based on a set of heuristic rules to restructure a semistructured schema into a normal form. These design methods also provide insights into the normalization task for semistructured databases.

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NF-NR: A practical normal form for nested relations

Cited by 17 publications

References 11 publications

Evaluations of Conceptual Models for Semi-structured Database System

Evaluations of Conceptual Models for Semi-structured Database System

Nest and Unnest Operators in Nested Relations

NF-SS: A Normal Form for Semistructured Schema

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