Context date October 2009 Glue semantics , or simply Glue Dalrymple et al. 1993 Dalrymple 1999, 2001 is a linguistic theory of semantic composition and the syntax semantics interface which assumes that meaning composition is constrained by a set of instructions stated within a formal logic, Linear logic . These instructions, called meaning constructors , state how the meanings of the parts of a sentence can be combined to provide the meaning of the sentence. Glue was developed as a theory of the syntax semantics interface within the linguistic theory of Lexical functional grammar , and most work within Glue has been conducted within that framework. LFG Glue assumes that the syntactic structure that is most relevant for meaning assembly is the functional structure, a structure which represents abstract syntactic predicate argument structure and relations like subject and object. In this setting, a meaning constructor for an intransitive verb states that the verb combines with the meaning of its subject to produce a meaning for the sentence. This is similar in some respects to the view of the syntax semantics interface assumed within categorial grammar , except that abstract syntactic ... grammar , and Tree adjoining grammar . Glue is a theory of the syntax semantics interface which is compatible not only with various syntactic frameworks, but also with different theories of semantics ... Semantics analyses include versions of Discourse Representation Theory , Intensional logic , First ... semantics via constraints . In Proceedings of the Sixth Meeting of the European ACL pp. 97 105 . University of Utrecht. Dalrymple, Mary Ed. . 1999 . Semantics and syntax in Lexical Functional Grammar ... Functional Grammar, No. 42 in Syntax and Semantics Series. New York Academic Press. ISBN 0126135347 External links http users.ox.ac.uk lina1301 GlueBibliography.htm Glue Semantics Bibliography Category Semantics nl Lijmsemantiek ... more details
In computer science , having value semantics also value type semantics or copy by value semantics means for an object that only its value counts, not its identity. ref cite web accessdate 2011 06 17 location http www.velocityreviews.com publisher velocity reviews title Some Basic QUESTIONS quote The important consideration for value semantics is that only the value of an object is significant, not its identity. So you can copy it copy constructor or assignment as much as you like, and any copy can be used in place of the original with no change. url http www.velocityreviews.com forums t677086 some basic questions.html ref ref cite web accessdate 2011 06 17 author Daniel Elstner location http mail.gnome.org publisher GTK & GNOME Mailing Lists title Re extending Gdk Region quote What are value semantics? ... It s an ad hoc shorthand for value type semantics , or copy by value semantics . url http mail.gnome.org archives gtkmm list 2009 May msg00107.html ref The concept in software design, like in the Standard Template Library for C to some extend. If the concept is fully applied, value semantics implies immutability of the object. ref cite web accessdate 2011 06 17 location http www.velocityreviews.com publisher velocity reviews title Some Basic QUESTIONS quote An object represents an immutable value vs. an object represents a system with a mutable state. ... Not necessarily, at least not in C . I do like the idea that an object with value semantics can only be modified by the assignment operators, but this is far from the general case std string, for example, clearly has value semantics, despite a large number of mutator functions. One can argue that this is a design error, but if so, it s still one we have to live with. url http www.velocityreviews.com forums t677086 some basic questions.html ref The concepts that are used to explain this concept are extensionality , definiteness ... semantics is that only the value of an object is significant, not its identity. So you can copy it copy ... more details
In computer science , particularly in human computer interaction , presentation semantics specify how a particular piece of a formal language is represented in a distinguished manner accessible to human senses , usually human vision. For example, saying that code nowiki bold ... bold nowiki code must render the text between these constructs using some bold typeface is a specification of presentation semantics for that syntax . An example of interactive presentation semantics is defining the expect behavior of a Hyperlink hypertext link on a suitable syntax. Many markup languages like HTML , CSS , DSSSL , XSL FO or troff have presentation semantics, but others like XML , XLink and XPath do not. ref H. P. Alesso, Craig Forsythe Smith, Developing Semantic Web services , A K Peters, Ltd., 2005, ISBN 1568812124, p. 62 and p. 100 ref ref G. Ken Holman, Definitive XSL FO , Prentice Hall PTR, 2003, ISBN 0131403745, p. 13 ref ref Erik Wilde, David Lowe, Xpath, XLink, XPointer, and XML a practical guide to Web hyperlinking and transclusion , Addison Wesley, 2003, ISBN 0201703440, p. 201 ref Character encoding standards like Unicode also have presentation semantics. ref http publib.boulder.ibm.com infocenter printer v1r1 index.jsp?topic com.ibm.printers.infoprintfonts com.ibm.printers.usingopentypefontsinanafpsystem g3a02mst18.htm ref One of the main goals of style sheet language s like CSS is to separate the syntax used to define structured data from the syntax endowed with presentation semantics that is used to render the data in various ways. References reflist compu sci stub Category Semantics Category Human computer interaction Category Programming language topics ... more details
Situation semantics , pioneered by Jon Barwise and John Perry philosopher John Perry in the early 1980s ref Jon Barwise and John Perry philosopher John Perry , Situations and Attitudes , 1983. MIT Press, ISBN 0 262 02189 7 ref , attempts to provide a solid theoretical foundation for reasoning about common sense and real world situations, typically in the context of theoretical linguistics, philosophy, or applied natural language processing , Barwise and Perry Situations, unlike worlds, are not complete in the sense that every proposition or its negation holds in a world. According to Situations and Attitudes , meaning is a relation between a discourse situation, a connective situation and a described situation. The original theory of Situations and Attitudes soon ran into foundational difficulties. A reformulation based on Peter Aczel s non well founded set theory ref Barwise, Jon. 1989. The Situation in Logic. CSLI Lecture Notes 17. Center for the Study of Language CSLI ref was proposed by Barwise before this approach to the subject petered out in the early 1990s. Situation semantics and HPSG Situation semantics is the first semantic theory that was used in Head driven phrase structure grammar HPSG . ref Carl Pollard Pollard, Carl and Ivan Sag Ivan A. Sag , 1987. Information Based Syntax and Semantics. Vol. 1 Fundamentals . CSLI Lecture Notes 13. CSLI, Stanford, CA. ref Angelika Kratzer Barwise and Perry s system was a top down approach which foundered on practical issues which were early identified by Angelika Kratzer and others. She subsequently developed a considerable ... in discourse and the syntax semantics interface ref http people.umass.edu kratzer Umass Faculty Member .... February 14, 2005 ref . See also Circumscription logic Discourse Semantics Situation theory Notes references External links http plato.stanford.edu entries situations semantics Situations in Natural Language Semantics Stanford Encyclopedia of Philosophy DEFAULTSORT Situation Semantics Category Semantics ... more details
Neighborhood semantics , also known as Scott Montague semantics , is a formal semantics for modal logics. It is a generalization, developed independently by Dana Scott and Richard Montague , of the more widely known Kripke semantics relational semantics for modal logic. Whereas a Kripke frame relational frame math langle W,R rangle math consists of a set W of worlds or states and an accessibility relation R intended to indicate which worlds are alternatives to or, accessible from others, a neighborhood frame math langle W,N rangle math still has a set W of worlds, but has instead of an accessibility relation a neighborhood function math N W to 2 2 W math that assigns to each element of W a set of subsets of W . Intuitively, each family of subsets assigned to a world are the propositions necessary at that world, where proposition is defined as a subset of W i.e. the set of worlds at which the proposition is true . Specifically, if M is a model on the frame, then math M,w models square A Longleftrightarrow A M in N w , math where math A M u in W mid M,u models A math is the truth set of A . Neighborhood semantics is used for the classical modal logics that are strictly weaker than the normal modal logic K . Correspondence between relational and neighborhood models To every relational model M W,R,V there corresponds an equivalent in the sense of having point wise equivalent modal theories neighborhood model M W,N,V defined by math N w A M M,w models Box A . math The fact that the converse fails gives a precise sense to the remark that neighborhood models are a generalization of relational ones. Another perhaps more natural generalization of relational structures are general frame general relational structures . References Scott, D. Advice in modal logic , in Philosophical Problems in Logic , ed. Karel Lambert. Reidel, 1970. Montague, R. Universal Grammar , Theoria 36, 373 98, 1970. Chellas, B.F. Modal Logic . Cambridge University Press, 1980. Category Modal logic logic ... more details
Naive semantics is an approach used in computer science for knowledge representation representing basic knowledge about a specific domain, and has been used in applications such as the representation of the meaning of natural language sentences in artificial intelligence applications. In a general setting the term has been used to refer to the use of a limited store of generally understood knowledge about a specific domain in the world, and has been applied to fields such as the knowledge based design of data schemas. ref Naive Semantics to Support Automated Database Design , IEEE Transactions on Knowledge and Data Engineering Volume 14 , issue 1 January 2002 by V. C. Storey, R. C. Goldstein and H. Ullrich http portal.acm.org citation.cfm?id 628188 ref In natural language understanding , naive semantics involves the use of a lexicon lexical theory which maps each word sense to a simple theory or set of assertions about the objects or events of reference. In this sense, naive semantic is based upon a particular language, its syntax and its word senses. For instance the word water and the assertion water X may be associated with the three predicate logic predicates clear X , liquid X and tasteless X . References Naive semantics for natural language understanding by Kathleen Dahlgren 1988 ISBN 0898382874 Notes Reflist Compu AI stub Category Natural language processing ... more details
distinguish General semantics Generative semantics is the name of a research program within linguistics , initiated by the work of various early students of Noam Chomsky John R. Ross , Paul Postal and later ... of deep structure . br A number of ideas from later work in generative semantics have been ... to semantics semantic interpretation . This assumption, combined with a tendency to consider a wider ... and semantics . &ldquo Interpretive&rdquo vs. &ldquo generative&rdquo semantics The controversy surrounding generative semantics stemmed in part from the competition between two fundamentally different approaches to semantics within transformational generative syntax. The first semantic theories ... entirely autonomous with respect to semantics, and was the approach preferred by Chomsky. In contrast ... semantics seemed rather clunky and ad hoc in comparison. This was especially so before the development ... of whose idea generative semantics was. All of the people mentioned here have been credited with its ... Brame, Michael K.. 1976 . Conjectures and refutations in syntax and semantics . New York North ... . New York Harper and Row. Dougherty, Ray C. 1974 . Generative semantics methods A Bloomfieldian ... descriptions . Cambridge, MA MIT Press. Lakoff, George. 1971 . On generative semantics. In D. D. Steinberg & L. A. Jakobovits Eds. , Semantics An interdisciplinary reader in philosophy, linguistics ... generative semantics. In J. D. McCawley Ed. pp. 43 61 . Lakoff, George & Ross, John R. H j . 1976 . Is deep structure necessary?. In J. D. McCawley Ed. , Syntax and semantics 7 pp. 159 164 . McCawley, James D. 1975 . Discussion of Ray C. Dougherty s Generative semantics methods A Bloomfieldian counterrevolution .... . 1976a . Syntax and semantics 7 Notes from the linguistic underground . New York Academic Press. McCawley ... . Doubl ing. In J. Kimball Ed. , Syntax and semantics Vol. 1, pp. 157 186 . New York Seminar Press ... 5. Category Generative linguistics Category Grammar frameworks Category Semantics Category Syntax de ... more details
Seme , the smallest unit of meaning recognized in semantics , refers to a single characteristic of a sememe . These characteristics are defined according to the differences between sememes. The term was introduced by Eric Buyssens in the 1930s and developed by Bernard Pottier in the 1960s. It is the result produced when determining the minimal elements of meaning, which enables one to describe word s multilingually. Such elements provide a bridge to component analysis and the initial work of ontologies . See also Memetics Mimicry Further reading http www.limsi.fr Individu jps research weakaliens doc 03.R 4.wap.func.oct03.pdf Functional Approach to Semantic Heterogeneity http www.google.com search?as q 22ontological semantics and the study of meaning in linguistics 22&hl en&num 100&btnG Google Search&as epq &as oq &as eq &lr lang en&cr &as ft i&as filetype &as qdr all&as nlo &as nhi &as occt any&as dt i&as sitesearch &as rights &safe images Ontological Semantics and the Study of Meaning in Linguistics, Philosophy and Computational Linguistics Lexicography Category Semantic units ling stub ar be x old de Sem Linguistik et Seem fr S me gl Semema it sema ru ... more details
orphan date December 2008 Failure semantics is a concept used in distributed computing to describe and classify error errors that distributed systems can experience. ref Flaviu Christian, Understanding Fault Tolerant Distributed Systems http citeseerx.ist.psu.edu viewdoc summary?doi 10.1.1.30.591 ref ref cite book author Arno Puder coauthors Kay Romer, Frank Pilhofer title Distributed Systems Architecture publisher Morgan Kaufmann year 2005 isbn 1558606483 , pp 14 16. ref Types of errors A list of types of errors that can occur An omission error is when one or more responses fails. A computer crash crash error is when nothing happens. A crash is a special case of omission when all responses fails. A timing error is when one or more responses arrive outside the time interval specified. Timing errors can be early or late . An omission error is a timing error when a response has infinite timing error. An arbitrary error is any error, i.e. a wrong value or a timing error . When a client uses a server computing it can cope with different type errors from the server. If it can manage a crash at the server it is said to assume the server to have crash failure semantics. If it can manage a service omission it is said to assume the server to have omission failure semantics. Failure semantics are the type of errors are expected to appear. Should another type of error appear it will lead to a service failure because it cannot be managed. References reflist Category Failure Category Distributed computing problems ... more details
linguistics Statistical semantics is the study of how the statistical patterns of human word usage can be used to figure out what people mean, at least to a level sufficient for information access George Furnas Furnas , 2006 . How can we figure out what words mean, simply by looking at patterns of words in huge collections of text? What are the limits to this approach to understanding words? History The term Statistical Semantics was first used by Warren Weaver Weaver 1955 in his well known paper on machine translation . He argued that word sense disambiguation for machine translation should be based on the co occurrence frequency of the context words near a given target word. The underlying ... . Delavenay 1960 defined Statistical Semantics as Statistical study of meanings of words and their frequency ... contribution to Statistical Semantics. An early success in the field was Latent semantic analysis Latent Semantic Analysis . Applications of statistical semantics Research in Statistical Semantics has resulted in a wide variety of algorithms that use the Distributional Hypothesis to discover many aspects of semantics , by applying statistical techniques to Text corpus large corpora ... and Littman, 2003 Related fields Statistical Semantics focuses on the meanings of common words ..., document collections, or named entities names of people, places, and organizations . Statistical Semantics is a subfield of computational semantics , which is in turn a subfield of computational linguistics and natural language processing . Many of the applications of Statistical Semantics listed ... of Statistical Semantics. One advantage of corpus based algorithms is that they are typically ..., and Dumais, S.T. 1983 . Statistical semantics Analysis of the potential performance of keyword information ... Translation of Languages , Cambridge, MA MIT Press. ISBN 0 8371 8434 7 DEFAULTSORT Statistical Semantics ... retrieval Category Semantics Category Statistical natural language processing Category Fields ... more details
Game semantics lang de dialogische Logik is an approach to Formal semantics logic formal semantics that grounds the concepts of truth or validity on game theory game theoretic concepts, such as the existence ... of Obligationes . In the late 1950s Paul Lorenzen was the first to introduce a game semantics for logic ... game semantics have been studied in logic. Shahid Rahman Lille and collaborators developed ... science , computational linguistics , artificial intelligence and the formal semantics of programming ..., L. Ong, H. Prakken, G. Sandu D. Walton, and J. Woods who placed game semantics in the center of new ... The simplest application of game semantics is to propositional logic . Each formula of this language ... players. More generally, game semantics may be applied to predicate logic the new rules allow ... logic, denotational semantics, linear logic, logical pluralism The primary motivation for Lorenzen and Kuno Lorenz was to find a game theoretic their term was dialogical Dialogische Logik semantics ... Bot generated title ref was the first to point out connections between game semantics and linear logic ... game semantics, the authors mentioned above have solved the long standing problem of defining a fully ... . Consequently, game semantics has led to fully abstract semantic models for a variety of programming ... ref Quantifiers Foundational considerations of game semantics have been more emphasised by Jaakko ... semantics. To get around this problem, the quantifiers were given a game theoretic meaning. Specifically ... a compositional semantics and proved it equivalent to game semantics for IF logics. Foundational ... logic . Journal of Symbolic Logic 59 1994 543 574. A. Blass, A game semantics for linear logic . Annals ... LICS.2009.26 Applications of Game Semantics From Program Analysis to Hardware Synthesis . 2009 24th ... arxiv.org abs cs.LO 0507045 In the beginning was game semantics . In Ondrej Majer, Ahti Veikko Pietarinen ... japaridz CL gsoll.html Game Semantics or Linear Logic? http plato.stanford.edu entries ... more details
Infobox album See Wikipedia WikiProject Albums Name Semantics Type EP Artist Australian Crawl Cover Semantics.jpg Caption 1983 Australian EP release by EMI Released 10 October 1983 Recorded Rhinoceros Studios Sydney, New South Wales Sydney br AAV studios Melbourne, Victoria Melbourne Genre Surf rock Length 17 53 Extended play EP br 44 09 LP album LP Label EMI EMI Australia Australia br Geffen Records Geffen United States U.S. Producer Mark Opitz Last album This album Next album Misc Singles Name Semantics Type EP single 1 Reckless Australian Crawl song Reckless Don t Be So single 1 date 1983 Extra album cover Upper caption Semantics Type compilation Cover AC semantics.jpg Lower caption 1984 European release Geffen Records Border Album ratings rev1 Allmusic rev1score Rating 4.5 5 ref Allmusic class album id r29557 pure url yes Allmusic review ref Automatically generated by DASHBot Semantics was a 1983 Extended play EP by iconic ref name HoF cite web url http www.ariaawards.com.au history ... Semantics was released in 1984 by Geffen Records as an expanded version LP album LP featuring the EP ... play , Semantics in 1983, ref name Kent ref name ARDb which achieved number 1 on the Kent Music ... ARDb Semantics contained the track Reckless Australian Crawl song Reckless Don t Be So , which some ... peaked at number 2. ref name Kent Geffen released Semantics , internationally, as a long play ... cite web url Allmusic class album id r29557 pure url yes title Semantics Overview last Schnee first ... Zentrum Track listing Semantics EP Reckless Australian Crawl song Reckless Don t Be So James Reyne ... worksearch.axd?q Looking 20for 20Cool accessdate 28 April 2009 ref 4 15 Semantics LP The Boys ... accessdate 28 April 2009 ref 5 14 from Sirocco Semantics Cassette Includes bonus song not available ... references Australian Crawl DEFAULTSORT Semantics Album Category Australian Crawl albums Category 1983 EPs pt Semantics ... more details
A semantics encoding is a translation between formal language s. For programmers, the most familiar form of encoding is the compilation of a programming language into machine code or byte code. Conversion between document formats are also forms of encoding. Compilation of TeX or LaTeX documents to PostScript are also commonly encountered encoding processes. Some high level preprocessors such as OCaml s Camlp4 or Apple Computer s WorldScript also involve encoding of a programming language into another. Formally, an encoding of a language A into language B is a mapping of all terms of A into B. If there is a satisfactory encoding of A into B, B is considered at least as powerful or at least as expressive as A. Properties An informal notion of translation is not sufficient to help determine expressivity of languages, as it permits trivial encodings such as mapping all elements of A to the same element of B. Therefore, it is necessary to determine the definition of a good enough encoding. This notion varies with the application. Commonly, an encoding math cdot A longrightarrow B math is expected to preserve a number of properties. Preservation of compositions soundness For every n ary operator math op A math of A, there exists an n ary operator math op B math of B such that math forall T A 1,T A 2, dots,T A n, op A T A 1,T A 2, cdots,T A n op B T A 1 , T A 2 , cdots, T A n math completeness For every n ary operator math op A math of A, there exists an n ary operator math op B math of B such that math forall T B 1,T B 2, dots,T B n, exists T A 1, dots,T A n, op B T B 1, cdots,T B N op A T A 1,T A 2, cdots,T A n math Note as far as the author is aware of, this criterion of completeness is never used. Preservation of compositions is useful insofar as it guarantees that components ... semantics of the programming language. Preservation of termination This also assumes the existence ... Compiler Semantics Semantic dictionary encoding SDE External links http catamaran.labs.cs.uu.nl ... more details
of semantic processes at the level of both words and sentences References cz Musical semantics ... Musical Semantics Category Semantics ... more details
orphan date August 2009 An extension agency is an organisation that practises Extensionsemanticsextension , in the context of community development . An example is the Cooperative Extension Service , which aims to assist individuals or groups in defining and achieving their goals in rural communities in the USA. Extension agents are trained in the skills of extension, such as communication and group facilitation, and usually in technical areas of the sector they serve for example agriculture, health, or safety . Agricultural extension agencies promote more profitable and sustainable farming, while health extension agencies promote improved health. Extension agents are represented by professional organisations such as the http www.apen.org.au Australasia Pacific Extension Network and publish in journals such as the http www.joe.org Journal of Extension . DEFAULTSORT Extension Agency Category Urban studies and planning ... more details
Unreferenced date December 2009 In Formal semantics logic formal semantics , truth value semantics is an alternative to Semantic theory of truth Tarskian semantics . It has been primarily championed by Ruth Barcan Marcus , H. Leblanc, and M. Dunn and N. Belnap. It is also called the substitution interpretation of the quantifiers or substitutional quantification. The idea of these semantics is that universal quantifier universal existential quantifier may be read as a conjunction disjunction of formulas in which constants replace the variables in the scope of the quantifier. E.g. xPx may be read Pa & Pb & Pc &... where a,b,c are individual constants replacing all occurrences of x in Px. The main difference between truth value semantics and the standard semantics for predicate logic is that there are no domains for truth value semantics. Only the truth clause s for atomic and for quantificational formulas differ from those of the standard semantics. Whereas in standard semantics atomic formula s like Pb or Rca are true if and only if the referent of b is a member of the extension of the predicate P, resp., if and only if the pair c,a is a member of the extension of R, in truth value semantics the truth values of atomic formulas are basic. A universal existential formula is true if and only if all some substitution instances of it are true. Compare this with the standard semantics which says that a universal existential formula is true if and only if for all some members of the domain ... of the domain. Truth value semantics is not without its problems. First, the strong completeness ... and the strong completeness theorem fail for truth value semantics. This is rectified by a modified ... instance in which the constant designates something that exists. See also Game semantics Kripke semantics Model theoretic semantics Proof theoretic semantics Truth conditional semantics Category Semantics DEFAULTSORT Truth Value Semantics zh ... more details
Central extension may refer to Central Extension Long Island Rail Road , a rail line Central extension mathematics , a type of group extension disambig ... more details
Western Extension is generally used for any westward expansion of a road, rail line or populated place. It may also have one of the following meanings The Western Extension of the Pennsylvania Turnpike Western Extension Baltimore and Harrisburg Railway Western Extension of a Maryland railroad South Carolina Western Extension Railway Western Extension Area Disambig ... more details
In mathematics , more specifically in ring theory , a ring extension or extension ring is a ring mathematics ring R with a subring S . We write R S and say R is a ring extension of S Given an extension R S of commutative rings and a prime ideal P of R , it follows that the intersection, say p , of P with S is a prime ideal of S . In this case we say that P lies over p . The situation is more complicated when R is not commutative. Examples A field extension is a special case of ring extension. See also Integral extension Group extension Algebraic extension Ore extension References MathWorld title Extension Ring id ExtensionRing Category Ring theory Abstract algebra stub eo Ringa vastiga o it Estensione di anelli nl Ringuitbreiding ... more details
Unreferenced date January 2011 In field theory mathematics field theory , a branch of algebra, primary extension L of K is a field extension such that the algebraic closure K in L is purely inseparable over K . A subextension of a primary extension is primary. A primary extension of a primary extension is primary transitivity . A primary extension of a perfect field is regular extension regular . Category Field theory Abstract algebra stub ... more details
Web Services Semantics WSDL S is a proposed extension to the Web Services Description Language WSDL standard. WSDL S extends standard WSDL to include semantic elements which should improve the reusability of Web Services by facilitating the composition of services, improving discovery, and enabling the integration of legacy software with a Web Services framework. WSDL S was developed by IBM and the University of Georgia . ref Cite web url http www.w3.org Submission WSDL S title W3C Web Service Semantics WSDL S accessdate 2007 07 13 format work ref See also List of Web service specifications References references Category Web service specifications compu network stub br ... more details
Extension service can refer to the following Agricultural extension services Cooperative extension service Church Multi site church extension service disambig Short pages monitor This long comment was added to the page to prevent it being listed on Special Shortpages. It and the accompanying monitoring template were generated via Template Longcomment. Please do not remove the monitor template without removing the comment as well. ... more details
Image ExtensionTube5733.jpg right thumb A set of extension tubes with a pen illustrating the lack of internal lenses An extension tube also called extension ring is used with lens mount interchangeable lenses to focus optics focus closer, useful in macro photography . ref http www.cambridgeincolour.com tutorials macro extension tubes closeup.htm MACRO EXTENSION TUBES & CLOSE UP LENSES ref Next 2 sentences copied from macro photography article The tube contains no optical elements its sole purpose is to move the lens farther from the image plane. The farther away the lens is, the closer the focus, the greater the magnification, and also the greater the loss of light requiring a longer exposure ... or sensor an extension tube simply imposes this movement. Extension tubes without electrical ... control. More expensive extension tubes contain electrical contacts allowing the user to use autofocus ... kenko slrc 04.html Kenko DG Teleplus Extension Tube Set ref An advantage to the non electrical tubes is their lower price. Other items like lens adapters may unintentionally have an effect similar to an extension ... when a lens adapter places the sensor too far away. Versus teleconverters Extension tubes are sometimes ... effective focal length. See also Canon Extension Tube List of Nikon compatible lenses with integrated autofocus motor Lens extension tube Kenko extension tubes for Nikon F mount References reflist External links http enchantingkerala.org digital photography school diy extension tube macro photography.php DIY Extension Tube How to easily build your own extension tube. http www.the digital picture.com Reviews Canon EF 25mm Extension Tube II Review.aspx Canon EF 25mm Extension Tube II review ..., Chapter Extension tubes at Nikonians.org http www.shutterfreaks.com Tips ExtensionTube.htm Extension ... picture.com Reviews Kenko Extension Tube Set Review.aspx Kenko Extension Tube Set review at http www.the ... Experiments with Close up Lenses and Extension Tubes Spoken Wikipedia En extension tube article.ogg ... more details
In abstract algebra , an abelian extension is a Galois extension whose Galois group is abelian group abelian . When the Galois group is a cyclic group , we have a cyclic extension . More generally, a Galois extension is called solvable if its Galois group is solvable group solvable . Any finite extension of a finite field is a cyclic extension. The development of class field theory has provided detailed information about abelian extensions of number field s, function field of an algebraic variety function fields of algebraic curve s over finite fields, and local field s. There are two slightly different concepts of cyclotomic extension s these can mean either extensions formed by adjoining roots of unity , or subextensions of such extensions. The cyclotomic field s are examples. Any cyclotomic extension for either definition is abelian. If a field K contains a primitive n th root of unity and the n th root of an element of K is adjoined, the resulting so called Kummer extension is an abelian extension if K has characteristic p we should say that p doesn t divide n , since otherwise this can fail even to be a separable extension . In general, however, the Galois groups of n th roots of elements operate both on the n th roots and on the roots of unity, giving a non abelian Galois group as semi direct product . The Kummer theory gives a complete description of the abelian extension case, and the Kronecker Weber theorem tells us that if K is the field of rational number s, an extension is abelian if and only if it is a subfield of a field obtained by adjoining a root of unity. There is an important analogy with the fundamental group in topology , which classifies all covering spaces of a space abelian covers are classified by its abelianisation which relates directly to the first ... min title cyclotomic extension Category Field extensions Category Algebraic number theory Category Class field theory de Abelsche Erweiterung es Extensi n abeliana fr Extension ab lienne nl Abelse uitbreiding ... more details
In mathematics , a Galois extension is an Algebraic extension algebraic field extension E F satisfying certain conditions described below one also says that the extension is Galois . The significance of being a Galois extension is that the extension has a Galois group and obeys the fundamental theorem of Galois theory . The definition is as follows. An algebraic field extension E F is Galois if it is normal extension normal and separable extension separable . Equivalently, the extension E F is Galois if and only if it is algebraic extension algebraic , and the fixed field field fixed by the automorphism group Aut E F is precisely the base field F . See the article Galois group for definitions of some of these terms and some examples. A result of Emil Artin allows one to construct Galois extensions as follows If E is a given field, and G is a finite group of automorphisms of E , then E F is a Galois extension, where F is the fixed field of G . Characterization of Galois extensions An important theorem of Emil Artin states that for a finite extension E F , each of the following statements is equivalent to the statement that E F is Galois E F is a normal extension and a separable extension . E is a splitting field of a separable polynomial with coefficients in F . E F Aut E F that is, the degree field theory degree of the field extension is equal to the order group theory order of the automorphism group of E F . Examples Adjoining to the rational number field the square root of 2 gives a Galois extension, while adjoining the cube root of 2 gives a non Galois extension. Both these extensions are separable, because they have characteristic zero . The first of them is the splitting field of X sup 2 sup &minus 2 the second has Normal extension normal closure that includes the complex ... Extension Category Galois theory Category Algebraic number theory Category Field extensions ca Extensi de Galois es Extensi n de Galois fr Extension de Galois it Estensione di Galois he ... more details
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