Relational Algebra

The main contents of the chapter consist of the following: The relational algebra, unary relational operations, relational algebra operations from set theory, binary relational operations, ER-to-Relational mapping algorithm, mapping EER model constructs to relations.

40p nanhankhuoctai10 23-07-2020 20 2   Download

In this paper, we present a definition of fuzzy multivalued dependencies in fuzzy databases with linguistic data based on similarity relation which is built by partitioning the domain of attribute values corresponding to an appropriate hedge algebra. Some properties of fuzzy multivalued dependencies are studied. Finally, the set of inference rules is shown to be sound and complete for a relation scheme class when it satisfies some specified conditions.

15p binhminhmuatrenngondoithonggio 09-06-2017 52 1   Download

Fuzzy databases with linguistic data based on hedge algebras were introduced, where the evaluation of queries containing linguistic data was transformed into that of traditional queries. On this new viewpoint, in this paper a notion of linear functional dependencies in these databases will be defined reasonably. The problems related to increasingly and decreasingly linear functional dependencies will be considered.

12p binhminhmuatrenngondoithonggio 09-06-2017 27 2   Download

In this paper, we introduced a method to approximate data on domain of fuzzy attributes in relation of fuzzy databases based hedge algebra. Because, domain of fuzzy attributes can except values are number, linguistic values, thus we have to effect and simply on method to approximate data.

12p binhminhmuatrenngondoithonggio 09-06-2017 39 4   Download

In this paper, we propose a new approach to overcome the limitations of the approach that is based on hedge algebra structure for building fuzzy object-oriented databases model. Some operators fuzzy object-oriented relation algebra are proposed corresponding with the model. Finally,we propose a method of fuzzy object-oriented query processing flexibly.

13p binhminhmuatrenngondoithonggio 09-06-2017 40 3   Download

This paper introduces a probabilistic relational database model, called PRDB, for representing and querying uncertain information of objects in practice. To develop the PRDB model, first, we represent the relational attribute value as a pair of probabilistic distributions on a set for modeling the possibility that the attribute can take one of the values of the set with a probability belonging to the interval which is inferred from the pair of probabilistic distributions

17p dieutringuyen 07-06-2017 35 1   Download

In this chapter we discuss the two formal languages for the relational model: the relational algebra and the relational calculus. The main contents in this chapter include: Example database application (COMPANY), overview of the QBE language (appendix D),...

53p kiepnaybinhyen_04 15-12-2015 52 3   Download

Có 2 loại xử lý Làm thay đổi dữ liệu (cập nhật) Thêm mới, xóa và sửa Không làm thay đổi dữ liệu (rút trích) Truy vấn (query) Thực hiện các xử lý Đại số quan hệ (Relational Algebra) Biểu diễn câu truy vấn dưới dạng biểu thức Phép tính quan hệ (Relational Calculus) Biểu diễn kết quả SQL (Structured Query Language)

80p tet0202 19-02-2013 151 21   Download

We prove a blow-up formula for cyclic homology which we use to show that infinitesimal K-theory satisfies cdh-descent. Combining that result with some computations of the cdh-cohomology of the sheaf of regular functions, we verify a conjecture of Weibel predicting the vanishing of algebraic K-theory of a scheme in degrees less than minus the dimension of the scheme, for schemes essentially of finite type over a field of characteristic zero. Introduction The negative algebraic K-theory of a singular variety is related to its geometry. ...

26p dontetvui 17-01-2013 53 7   Download

We prove that the existence of an automorphism of finite order on a Q-variety X implies the existence of algebraic linear relations between the logarithm of certain periods of X and the logarithm of special values of the Γ-function. This implies that a slight variation of results by Anderson, Colmez and Gross on the periods of CM abelian varieties is valid for a larger class of CM motives. In particular, we prove a weak form of the period conjecture of Gross-Deligne [11, p. 205]1 .

29p tuanloccuoi 04-01-2013 61 9   Download

We devise a new criterion for linear independence over function fields. Using this tool in the setting of dual t-motives, we find that all algebraic relations among special values of the geometric Γ-function over Fq [T ] are explained by the standard functional equations. Contents 1. Introduction 2. Notation and terminology 3. A linear independence criterion 4. Tools from (non)commutative algebra

78p tuanloccuoi 04-01-2013 55 6   Download

To the memory of Rodica Simion The goals of this paper are two-fold. First, we prove, for an arbitrary finite root system Φ, the periodicity conjecture of Al. B. Zamolodchikov [24] that concerns Y -systems, a particular class of functional relations playing an important role in the theory of thermodynamic Bethe ansatz. Algebraically, Y -systems can be viewed as families of rational functions defined by certain birational recurrences formulated in terms of the root system Φ.

43p tuanloccuoi 04-01-2013 49 7   Download

The basic set of operations for the relational model is known as the relational algebra. These operations enable a user to specify basic retrieval requests. The result of a retrieval is a new relation, which may have been formed from one or more relations. The algebra operations thus produce new relations, which can be further manipulated using operations of the same algebra.

52p thienthanoze 12-11-2012 62 6   Download

ON THE ALGEBRAIC DIFFERENCE EQUATIONS un+2 un = ψ(un+1 ) IN R+ , RELATED TO A FAMILY ∗ OF ELLIPTIC QUARTICS IN THE PLANE G. BASTIEN AND M. ROGALSKI Received 20 October 2004 and in revised form 27 January 2005 We continue the study of algebraic difference equations of the type un+2 un = ψ(un+1 ), which started in a previous paper. Here we study the case where the algebraic curves related to the equations are quartics Q(K) of the plane. We prove, as in “on some algebraic difference equations un+2 un = ψ(un+1 ) in R+ , related to families of...

35p sting12 10-03-2012 33 5   Download

SMOOTH AND DISCRETE SYSTEMS—ALGEBRAIC, ANALYTIC, AND GEOMETRICAL REPRESENTATIONS ˇ FRANTISEK NEUMAN Received 12 January 2004 What is a differential equation? Certain objects may have different, sometimes equivalent representations. By using algebraic and geometrical methods as well as discrete relations, different representations of objects mainly given as analytic relations, differential equations can be considered.

10p sting12 10-03-2012 30 4   Download

In 1991, David Gale and Raphael Robinson, building on explorations carried out by Michael Somos in the 1980s, introduced a three-parameter family of rational recurrence relations, each of which (with suitable initial conditions) appeared to give rise to a sequence of integers, even though a priori the recurrence might produce non-integral rational numbers. Throughout the '90s, proofs of integrality were known only for individual special cases. In the early '00s, Sergey Fomin and Andrei Zelevinsky proved Gale and Robinson's integrality conjecture.

13p thulanh8 19-09-2011 67 4   Download

Tuyển tập các báo cáo nghiên cứu khoa học ngành toán học tạp chí Journal of Operator Theory đề tài: Về cấu trúc của (BCP)-nhà khai thác và đại số có liên quan...

11p matuot_266 27-08-2011 53 4   Download

Tuyển tập các báo cáo nghiên cứu khoa học ngành toán học tạp chí Journal of Operator Theory đề tài: Về cấu trúc của (BCP) nhà khai thác và đại số có liên quan...

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Đại số quan hệ (tiếng Anh: relational algebra) dùng phổ biến trong lí thuyết cơ sở dữ liệu quan hệ là một bộ các toán tử và các quy tắc tương ứng có thể được sử dụng để thao tác trên các toán học (relation) và tạo ra kết quả là một quan hệ khác.

29p cindy03 19-01-2011 79 16   Download

Xét một số xử lý trên quan hệ NHANVIEN: Thêm mới một nhân viên. Chuyển nhân viên có tên là “Tùng” sang phòng số 1. Cho biết họ tên và ngày sinh các nhân viên có lương trên 20000. Có 2 loại xử lý: Làm thay đổi dữ liệu (cập nhật), Thêm mới, xóa và sửa. Không làm thay đổi dữ liệu (rút trích), Truy vấn (query).

94p mrphanhoi 02-09-2010 406 87   Download