The paper surveys some recent work on formal aspects of the logic of theory change. It begins with a general discussion of the intuitive processes of contraction and revision of a theory, and of differing strategies f...
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The paper surveys some recent work on formal aspects of the logic of theory change. It begins with a general discussion of the intuitive processes of contraction and revision of a theory, and of differing strategies for their formal study. Specific work is then described, notably Gärdenfors' postulates for contraction and revision, maxichoice contraction and revision functions and the condition of orderliness, partial meet contraction and revision functions and the condition of relationality, and finally the operations of safe contraction and revision. Verifications and proofs are omitted, with references given to the literature, but definitions and principal results are presented with rigour, along with discussion of their significance
The article describes data compression on a database system. Compressing information in a database system is attractive for two major reasons: storage saving and performance improvement. Storage saving is a direct and...
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The article describes data compression on a database system. Compressing information in a database system is attractive for two major reasons: storage saving and performance improvement. Storage saving is a direct and obvious benefit, whereas performance improvement derives from the fact that less physical data need be moved for any particular operation on the database. Data in an Information Management System (IMS) database are stored as a set of segments (records). The IMS system makes provision for a data compression exit to be invoked whenever a segment is stored, and for a complementary expansion exit to be called whenever a segment is retrieved. Thus, compression and expansion exits become an integral part of the IMS system and are therefore heavily constrained. In this scenario, it is inconvenient for exit routines to have to determine any information about the format of a segment being processed, such as where the field boundaries are or what type of data the fields contain. Finally, because the exit routines become part of the IMS system and are loaded into common storage, a proliferation of different exits is undesirable: One pair of exits must apply to a very wide variety of data. Indeed, each exit should be able to handle all possible character sequences.
Abstract: In this paper the following result is proved. Let r, s and n be integers satisfying $0 \leqslant r < s < n$, $s > {n^{1/3}}$, $\gcd (r,s) = 1$. Then there exist at most 11 positi...
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Abstract: In this paper the following result is proved. Let r, s and n be integers satisfying $0 \leqslant r < s < n$, $s > {n^{1/3}}$, $\gcd (r,s) = 1$. Then there exist at most 11 positive divisors of n that are congruent to r modulo s. Moreover, there exists an efficient algorithm for determining all these divisors. The bound 11 is obtained by means of a combinatorial model related to coding theory. It is not known whether 11 is best possible; in any case it cannot be replaced by 5. Nor is it known whether similar results are true for significantly smaller values of $\log s/\log n$. The algorithm treated in the paper has applications in computational number theory.
Discusses a low-level approach to achieving efficiency in computer programming through code tuning which involves locating the expensive parts of an existing program and then modifying that code to improve its perform...
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Discusses a low-level approach to achieving efficiency in computer programming through code tuning which involves locating the expensive parts of an existing program and then modifying that code to improve its performance. Benefits of using code tuning; Discussion of problems that arise in several applications and the solutions which use general principles; Role of code tuning in large data processing shops.
We consider extensions of Peano arithmetic suitable for doing some of nonstandard analysis, in which there is a predicate N(x) for an elementary initial segment, along with axiom schemes approximating ω1-saturation. ...
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We consider extensions of Peano arithmetic suitable for doing some of nonstandard analysis, in which there is a predicate N(x) for an elementary initial segment, along with axiom schemes approximating ω1-saturation. We prove that such systems have the same proof-theoretic strength as their natural analogues in second order arithmetic. We close by presenting an even stronger extension of Peano arithmetic, which is equivalent to ZF for arithmetic statements.
This paper is a survey of matrix error correcting codes and presents existing theory for matrix code literature since 1950. A brief description of several contributions and books concerned with the theory relevant onl...
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This paper is a survey of matrix error correcting codes and presents existing theory for matrix code literature since 1950. A brief description of several contributions and books concerned with the theory relevant only to matrix codes is presented. Two and three dimensional arrays of digital information occur frequently in today's applications in digital communication systems, computer systems and automatia. The error control of such systems (like error detection and correction) is a fact that takes place for a variety of reasons. Matrix codes, which are a straight forward application of the one, two, or more dimensional arrays, have a great advantages over the other codes surveyed. These codes use a systematic specification with simple parity checking. For this reason we are giving a survey of the existing literature about matrix codes today with relevant comments. Most of the references used here are cited to illustrate these themes. [ABSTRACT FROM AUTHOR]
In this paper it is proved that the dual of a code of order r + (r + 1 )m,swhich is a linear code over GF(2) obtained by annexing some vectors to the basis vectors of an rth order Reed-Muller code R(r, m), is a code o...
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In this paper it is proved that the dual of a code of order r + (r + 1 )m,swhich is a linear code over GF(2) obtained by annexing some vectors to the basis vectors of an rth order Reed-Muller code R(r, m), is a code of order (m −r −2) + (m −r−1)m,swhereFurther, the weight distribution of such codes is obtained in some particular cases.
Let EG( m , 2) denote the m -dimensional finite Euclidean space (or geometry) based on GF(2), the finite field with elements 0 and 1. Let T be a set of points in this space, then T is said to form a q -covering (where...
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Let EG( m , 2) denote the m -dimensional finite Euclidean space (or geometry) based on GF(2), the finite field with elements 0 and 1. Let T be a set of points in this space, then T is said to form a q -covering (where q is an integer satisfying 1⩽ q ⩽ m ) of EG( m , 2) if and only if T has a nonempty intersection with every ( m - q )-flat of EG( m , 2). This problem first arose in the statistical context of factorial search designs where it is known to have very important and wide ranging applications. Evidently, it is also useful to study this from the purely combinatorial point of view. In this paper, certain fundamental studies have been made for the case when q =2. Let N denote the size of the set T . Given N , we study the maximal value of m .
Bounded rationality forces an entity to divide its responses between those it does immediately (called adaptedness) and those it does with delay (called adaptability). Information theory is used to show how coding is ...
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Bounded rationality forces an entity to divide its responses between those it does immediately (called adaptedness) and those it does with delay (called adaptability). Information theory is used to show how coding is related to the problem of choosing between adaptedness and adaptability.
A wide variety of different applications lead to problems in which sequences of different lengths must be compared, to see how different they are, and to see which elements in one sequence correspond to which elements...
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A wide variety of different applications lead to problems in which sequences of different lengths must be compared, to see how different they are, and to see which elements in one sequence correspond to which elements in the other sequence. Successful methods for handling these problems been repeatedly reinvented which incorporate two basic ideas a systematic concept of distance between sequences, and elegant recursive algorithms for doing the necessary computations. The major application areas are speech processing and macromolecular biology. Computer science is another significant application area, and applications have also been made to bird song, handwriting analysis, gas chromatography, geological strata, and text collation. This paper surveys the applications, methods and theory of sequence comparison.
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