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A candidate key (or minimal superkey) is a superkey that can't be reduced to a simpler superkey by removing an attribute. [ 3 ] For example, in an employee schema with attributes employeeID , name , job , and departmentID , if employeeID values are unique then employeeID combined with any or all of the other attributes can uniquely identify ...
A candidate key is a minimal superkey, [1] i.e., a superkey that does not contain a smaller one. Therefore, a relation can have multiple candidate keys, each with a different number of attributes. [2] Specific candidate keys are sometimes called primary keys, secondary keys or alternate keys.
Only S 1, S 2, S 3 and S 4 are candidate keys (that is, minimal superkeys for that relation) because e.g. S 1 ⊂ S 5, so S 5 cannot be a candidate key. Given that 2NF prohibits partial functional dependencies of non-prime attributes (i.e., an attribute that does not occur in any candidate key ) and that 3NF prohibits transitive functional ...
The law is, in a strict sense, only about correspondence; it does not state that communication structure is the cause of system structure, merely describes the connection. Different commentators have taken various positions on the direction of causality; that technical design causes the organization to restructure to fit, [ 10 ] that the ...
Examples of don't-care terms are the binary values 1010 through 1111 (10 through 15 in decimal) for a function that takes a binary-coded decimal (BCD) value, because a BCD value never takes on such values (so called pseudo-tetrades); in the pictures, the circuit computing the lower left bar of a 7-segment display can be minimized to a b + a c by an appropriate choice of circuit outputs for ...
By hypothesis, I-language—also called universal grammar—corresponds to the initial state of the human language faculty in individual human development. Minimalism is reductive in that it aims to identify which aspects of human language—as well the computational system that underlies it—are conceptually necessary.
A Super key, located between the Control key and the Alt key, on an ISO style PC keyboard. Super key ( ) is an alternative name for what is commonly labelled as the Windows key [1] or Command key [2] on modern keyboards, typically bound and handled as such by Linux and BSD operating systems and software today.
MARC - MAchine Readable Cataloging – standards for the representation and communication of bibliographic and related information in machine-readable form. METS [31] Librarianship: Metadata Encoding and Transmission Standard is an XML schema for encoding descriptive, administrative, and structural metadata regarding objects within a digital ...