Concepts inData exchange with arithmetic operations
Data exchange
Data exchange is the process of taking data structured under a source schema and actually transforming it into data structured under a target schema, so that the target data is an accurate representation of the source data. Data exchange is similar to the related concept of data integration except that data is actually restructured (with possible loss of content) in data exchange. There may be no way to transform an instance given all of our constraints.
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Arithmetic
Arithmetic or arithmetics is the oldest and most elementary branch of mathematics, used by almost everyone, for tasks ranging from simple day-to-day counting to advanced science and business calculations. It involves the study of quantity, especially as the result of operations that combine numbers. In common usage, it refers to the simpler properties when using the traditional operations of addition, subtraction, multiplication and division with smaller values of numbers.
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Schema matching
The terms schema matching and mapping are often used interchangeably. For this article, we differentiate the two as follows: Schema matching is the process of identifying that two objects are semantically related (scope of this article) while mapping refers to the transformations between the objects. For example, in the two schemas DB1. Student (Name, SSN, Level, Major, Marks) and DB2. Grad-Student (Name, ID, Major, Grades); possible matches would be: DB1. Student ¿ DB2. Grad-Student; DB1.
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Axiom schema
In mathematical logic, an axiom schema generalizes the notion of axiom. An axiom schema is a formula in the language of an axiomatic system, in which one or more schematic variables appear. These variables, which are metalinguistic constructs, stand for any term or subformula of the system, which may or may not be required to satisfy certain conditions. Often, such conditions require that certain variables be free, or that certain variables not appear in the subformula or term.
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Conjunctive query
In database theory, a conjunctive query is a restricted form of first-order queries. A large part of queries issued on relational databases can be written as conjunctive queries, and large parts of other first-order queries can be written as conjunctive queries. Conjunctive queries also have a number of desirable theoretical properties that larger classes of queries (e.g. , the relational algebra queries) do not share.
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Algebraic number
In mathematics, an algebraic number is a number that is a root of a non-zero polynomial in one variable with rational coefficients (or equivalently¿by clearing denominators¿with integer coefficients). Numbers such as ¿ that are not algebraic are said to be transcendental; almost all real and complex numbers are transcendental. (Here "almost all" has the sense "all but a countable set"; see Properties below.)
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Database schema
A database schema of a database system is its structure described in a formal language supported by the database management system (DBMS) and refers to the organization of data to create a blueprint of how a database will be constructed (divided into database tables). The formal definition of database schema is a set of formulas (sentences) called integrity constraints imposed on a database. These integrity constraints ensure compatibility between parts of the schema.
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PSPACE
In computational complexity theory, PSPACE is the set of all decision problems which can be solved by a Turing machine using a polynomial amount of space.
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