The Nested Universal Relation Database ModelSpringer Science & Business Media, 1992 M05 20 - 177 páginas This monograph describes a method of data modelling whose basic aim is to make databases easier to use by providing them with logical data independence. To achieve this, the nested UR (universal relation) model is defined by extending the classical UR model to nested relations. Nested relations generalize flat relations and allow hierarchically structured objects to be modelled directly, whereas the classical UR model allows the user to view the database as if it were composed of a single flat relation. The author presents a comprehensive formalisation of the nested relational model, which incorporated null values into the model. Functional data dependencies and the classical notion of lossless decomposition are extended to nested relations and an extended chase procedure is defined to test the satisfaction of the data dependencies. The nested UR model is defined, and the classical UR model is shown to be a special case of the nested model.This implies that an UR interface canbe implemented by using the nested UR model, thus gaining the full advantages of nested relations over flat relations. |
Contenido
I | 1 |
III | 3 |
IV | 9 |
V | 11 |
VI | 12 |
VIII | 13 |
IX | 15 |
X | 18 |
XXIX | 67 |
XXX | 74 |
XXXI | 77 |
XXXII | 79 |
XXXIII | 81 |
XXXIV | 84 |
XXXV | 88 |
XXXVI | 94 |
XI | 19 |
XII | 21 |
XIII | 25 |
XIV | 26 |
XV | 29 |
XVII | 30 |
XVIII | 31 |
XIX | 32 |
XX | 35 |
XXI | 36 |
XXII | 37 |
XXIII | 42 |
XXIV | 45 |
XXV | 48 |
XXVI | 49 |
XXVII | 52 |
XXVIII | 58 |
XXXVII | 106 |
XXXVIII | 109 |
XXXIX | 111 |
XL | 122 |
XLI | 125 |
XLII | 128 |
XLIII | 134 |
XLIV | 137 |
XLV | 138 |
XLVI | 144 |
XLVII | 147 |
XLVIII | 153 |
XLIX | 157 |
L | 159 |
LI | 163 |
175 | |
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Términos y frases comunes
ATT(n Atzeni Bachman diagram CHASE(r CLASS EXAM Computer DBMS defined Definition denoted easily be verified EDOM empty node insertion empty set extended chase rules extended data dependencies extended nested relational Fagin FD(T FDS(F FF(T flat database HEIGHT(T hierarchical relations interface join dependencies joinable NDS Lemma Let R(T Levene & Loizou Maier MVD(T MVDs Naomi null NEFD-rule NEJD nested database nested flat relation nested relational model nested UR model nested weak instance NMVDs NRSS null extended algebra null extended data null extended join null extended nested null null null null values NURS possesses the UMC Proposition query R(T₁ r₁ r₂ relational algebra result root weighting running example Schek scheme tree semantics set of attributes set of null shown in Figure single nested relation Subsection superkey t₁ t₂ Theorem tuples Ullman UMC property UNNEST operators weak instance approach window function y-acyclic
Referencias a este libro
Uncertainty Management in Information Systems: From Needs to Solutions Amihai Motro,Philippe Smets Vista previa limitada - 1996 |