invention of the first computer mouse

How group work is used in speaking lesson of the first year major students of english at viet nam university of commerce

... the former, 83.3% of the teacher often grouped students of the same sex while only 20% of the students chose it and for the latter, group students of different sexes was the choice of 80% of ... understanding of using group work in the speaking lesson at VUC.1.2. Aims of the study The purpose of this study is to explore the reality of the use of group work in the speaking lesson of 1st- ... for the first- year students is 6. The number of the first- year English major students is estimated at more than 300. They come from various parts of the country. Their levels of English proficiency...

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Tài liệu Paper and Key of the first term test TQC Senor High School - Hoi An Town

Danh mục: Tiếng anh

... until the end after the invention of printing in the 15th century. The first significant decline in illiteracy came with the Reformation, when translation of the Bible into the vernacular became ... you mind if I turn off the air- conditioner? B. Do you have someone turn off the air-conditioner? C. Do you have the air-conditioner turn off? D. Do you delay turning off the air-conditioner?3. ... from the 18th to the 20th century generally included an attack on illiteracy as one of their goals, with the former Soviet Union, China, and Cuba being among the most successful in the 20th...

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Tài liệu Scene Of The Cybercrime Computer Forensics Handbook docx

Danh mục: Quản trị mạng

... Understanding Computer Basics 147Introduction 148Understanding Computer Hardware 149Looking Inside the Machine 150Components of a Digital Computer 150 The Role of the Motherboard 151 The Roles of the ... pictures of minors.All these acts are alreadycriminal in certain jurisdictions and could be committed without the use of the computer network .The “cyber”aspect is not a necessary element of the offense;it ... computer to commit them aswell as to those who commit them without the use of a computer or network.In other cases, the crime is unique and came into existence with the advent of the Internet. Unauthorized...

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ORDER OF BUSINESS of the first part of the 2007 Ordinary Session (22-26 January 2007) adopted by the Assembly on 22 January 2007 doc

Danh mục: Tài chính doanh nghiệp

... in the Chair: Mr Miguel Barceló Pérez (Spain, EPP/CD)) a. Examination of credentials (Doc. 11124) b. Election of the President of the Assembly c. Election of the Vice-Presidents of the ... moratorium on the death penalty by Council of Europe member states" f. Adoption of the order of business g. Adoption of the minutes of the meeting of the Standing Committee (17 November ... 7.30 p.m. End of the sitting - 2 - Monday 22 January 2007 8 a.m. Bureau of the Assembly 9.30 a.m. Political groups 11.30 a.m. 1. Opening of the first part of the 2007 Ordinary...

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Primary school THE TEST OF THE FIRST SEMMETER pdf

Danh mục: Tài liệu khác

...

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Apollonius of Tyana, the Philosopher-Reformer of the First Century A.D. potx

Danh mục: Cao đẳng - Đại học

... Lucian, the witty writer of the first half of the second century, makes the subject of one of his satires the pupil of a disciple of Apollonius, of one of those who were acquainted with "all the ... out of the fears of the citieson the left shores of the Hellespont. These cities had suffered severely from shocks of earthquake, and in theirpanic placed large sums of money in the hands of these ... purification of the many cults of the Empire and to the instruction of the ministers and priests of its religions. With the exception of the Christ no more interesting personageappears upon the stage of...

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So, you want to go to grad school in Economics? A practical guide of the first years (for outsiders) from insiders pptx

Danh mục: Cao đẳng - Đại học

... in the first year. Besides the professors, the TA’s of the courses you are taking in your first year are also an important part of the first year life. Don’t hesitate to talk to them. Go to their ... in terms of the general, and touch abstract and concrete in the same flight of thought. He must study the present in the light of the past for the purposes of the future. No part of man’s nature ... even further: It’s going to be the most difficult experience of your life. However, should you decide to go for it, the rewards are easily greater than the costs. The first moral of the story:...

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Báo cáo khoa học: "Contents and evaluation of the first Slovenian-German online dictionary" doc

Danh mục: Báo cáo khoa học

... equivalent in the other language, as many entries as necessary arecreated.3 Evaluation The evaluations of the Slovenian part of the dic-tionary concern its coverage of a) the corpus of the Slovenian ... method is a good approxi-mation of how much a dictionary user can under-stand of the lexical content of the newspaper text.In the case of non-related lemmas, one of themis usually much more frequent ... There are 2,428 such entries.3.1 Newspaper corpus coverageTo evaluate the coverage of texts by the Slove-nian side of the dictionary, we chose the wordformlist with frequencies of DELO, the...

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a bibliography of the personal computer electronic resource pdf

Danh mục: Kỹ thuật lập trình

...

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A quarterly bulletin of the IEEE computer society technical committee on Database engineering (VOL. 8) ppt

Danh mục: Cơ sở dữ liệu

... Figure5:Acquiring the VirtualRelationsPKCONTandHEMICwindowforquestionsandanswers.When the DBEuses the mouse toselectone of the itemsfrom the threemenus,aset of questionsappearsin the question-answeringareaat the bottom of the display,towhichhecanthenrespond.One of the generalprinciples of acquisitionisevidentfromthisdisplay,namely,that the acquisitioniscenteredupon the relationsandfieldsin the database,becausethisis the informationmostfamiliarto the DBE. The answerstoeachquestioncanaffect the lexicon, the conceptualschema,and the databaseschema. The DBEneednotbeaware of exactlywhyTEAMposes the questionsitdoes—allhehastodoisanswerthemcorrectly.Even the entriesdisplayedin the wordmenuowetheirpresencetoquestionsabout the database. The DBEvolunteersentriestothismenuonlyin the case of verbacquisition,tosupplyanadjectivecorrespondingtosomenounalreadyinTEAM’slexicon,ortoenterasynonymforsomelexicon-residentword. The DBEisassumednottohaveanyknowledge of formallinguisticsor of natural-languageprocessingmethods.Heisassumed,however,toknowsomegeneralfactsaboutEnglish—forexample,whatpropernouns,verbs,plurals,andtenseare,butnothingmoredetailedthanthat.Ifmoresophisticatedlinguisticinformationisrequired,asin the case of verbacquisition,TEAMproceedsbyaskingquestionsaboutsamplesentences,allowing the DBEtorelyonhisintuitionasanativespeaker,andextracting the informationitneedsfromhisresponses.Virtualrelationsarespecifiediconically. The leftside of Figure5shows the acquisition of avirtualrelationthatidentifies the continent(PKCONT-CONTINENT,derivedfromWORLDC-CONTINENT) of apeak(PKCONT-NAME,fromPEAK-NAME)byperformingadatabasejoinon the PEAK-COUNTRYandWORLDC-CONTINENTfields.Similarly, the rightside of Figure5shows the acquisition of the virtualrelationthatencodes the hemisphere(HEMIC-HEMI) of acountry(HEMIC.NAME)byjoiningon the WORLDC-CONTINENTandCONT-NAMEfields.Ifhewishes, the DBEcanchangepreviousanswers.Incrementalupdatesarepossiblebecausemost of the methodsforupdating the variousTEAMstructures(lexicon,schemata)weredevisedtoundo the effects of previousanswersbefore the effects of newanswerscouldbeasserted.Helpinformationisalwaysavailabletoassist the DBEwhenheisunsurehowtoansweraquestion.Selecting the questiontextwith the mouse producesamoreelaboratedescription of the informationTEAMistryingtoelicit,usuallyaccompaniedbypertinentexamples.Finally, the acquisitioncomponentkeepstrack of whatinformationremainstobesuppliedbeforeTEAMhas the minimumitneedstohandlequeries. The DBEdoesnothavetodeterminehimselfhowmuchinformationissufficient;allhehastodoistoperceivethatnoacquisitionwindowindicatesremainingunansweredquestions. Of course, the DBEcanalwaysprovideinformationbeyond the minimum—forexample,bysupplyingadditionalverbs,derivedadjectives,orsynonyms.—20— ... continent of the country.Likewise, the hemisphereinwhichacountryislocatedcanbedeterminedfrom the continentonwhich the countryislocatedand the hemisphere of thatcontinent.TEAMallows the DBEtospecifyvirtualrelationsthatconveysuchadditionalinformation.2 The TEAMSystemArchitecture The design of TEAMreflectsseveralconstraintsimposedby the demandfortransportability;ourdiscussionwillemphasizethoseaspects of the design. The needtodecouple the representation of whatausermeansbyaqueryfrom the procedureforobtainingthatinformationfrom the databaseobviouslyaffected the choice of systemcomponents.Inaddition, the needtoseparate the domain-dependentknowledgetobeacquiredforeachnewdatabasefrom the domain-independentparts of the systeminfluenced the design of the particulardatastructures(or“knowledgesources”)selectedforencoding the informationusedbythesecomponents.Figure2illustrates the majorprocesses of TEAM, the varioussources of knowledgetheyuse,and the flow of language-processingtasksfrom the analysis of anEnglishsentenceto the generation of adatabasequery. The rectangularboxesrepresent the processes,and the ovalstotheirright, the variousknowledgesources. The acquisitionboxon the rightpointstothoseknowledgesourcesthatareaugmentedthroughinteractionwith the DBE.AllothermodulesandknowledgesourcesarebuiltintoTEAMandremainunchangedduringacquisition.Inthissectionwewilllookat the TEAMsystemfromseveralangles.Tobegin,wewillsketch the overallflow of processingduringquestion-answering,describing the variousprocessesinvolvedintransforminganEnglishqueryintoaformaldatabasequery.Because the particularlogicalform(LF)TEAMusestoencode the meaning of aqueryplaysacrucialroleinmediatingbetween the wayqueriesareposedand the wayinformationisobtainedfrom the database,itaffects the design of severalcomponents of the system.Wethenlookinsomewhatmoredetailat the datastructuresthatencodedomain-specificinformation.Finally,wediscuss the overallstrategyusedforacquiringinformationaboutspecificdomainsanddatabases.2.1Flow of Control The flow of controlduringTEAM’stranslation of anatural-languagequeryintoaformalqueryto the databaseisillustratedas the pathon the leftside of Figure2,fromtoptobottom. The transformationtakesplaceintwomajorsteps: first, arepresentation of the literalmeaning of the query,orlogicalform,isconstructed;second,thislogicalformistransformedintoadatabasequery. The translationintologicalformisperformedby the DIALOGICsystem,whichcomprises the following-components,shownsurrounded-by the~ dotted~boxinFigure2: the DIAMONDparser, the DIAGRAMgrammar, the lexicon,semantic-interpretationfunctions,basicpragmaticfunctions,andproceduresfordetermining the scope of quantifiers.Sinceadescription of DIALOGICisprovidedelsewhereGrosS2],letusdiscusshereonlythoseaspects of the systemthatwereinfluencedby the development of TEAM.TwocentraldatastructuresinDIALOGICthatareaffectedbyTEAM’sacquisitionprocessaredescribed: the lexiconand—13— ... schema;7,hence, the choice of logicalformindirectlyaffects the design of thosecomponents of the systemanddetermines,inpart, the information the DBEmustsupply. The logicalformemployedbyTEAMis first- orderlogicextendedbycertainintensionalandhigher-orderoperatorsandaugmentedwithspecialquantifiersfordefinitedeterminersandinterrogativedeterminers.Muchresearchhasbeendonetodeviseappropriatelogicalformsformanykinds of sentencesMoor8l],butthatinvestigationliesbeyond the scope of thisarticle.2.3WhatInformationIsAcquired2.3.1 The Lexicon The lexiconisarepository of the informationabouteachwordthatisnecessaryformorphological,syntactic,andsemanticanalysis.Therearetwoclasses of lexicalitems:closedandopen.Closedclasses(e.g.,pronouns,conjunctions,anddeterminers)containonlyafinite,usuallysmallnumber of lexicalitems.Typically,thesewordshavecomplexandspecializedgrammaticalfunctions,alongwithatleastsome]fixedmeaningsthatareindependent of the domain.Theyarelikelytooccurwithhighfrequencyinqueriestoalmostanydatabase.Openclasses(e.g.,nouns,verbs,adjectives)aremuchlargerand the meanings of theirmemberstendtovary,dependingon the particulardatabaseanddomain.Therefore,mostclosed-classwordsarebuiltinto the initialTEAMlexicon,whileopen-classwordsareacquiredforeachdomainseparately.However,thereareanumber of open-classwords,suchasthosecorrespondingtoconceptsin the initialconceptualschema(seeSection2.3.2)andwordsforcommonunits of measure(e.g.,“meter”,“pound”),thataresobroadlyapplicabletosomanydatabasedomainsthattheyareincludedin the initiallexiconaswell.Lexicalentriesincludethosefor the names of filesubjects(i.e., the entitiesaboutwhichsomerelationcontainsinformation—e.g.,peaksforPEAK,andcountriesforWORLDCin the sampledatabaseillustratedinFigure1.3),fieldnames,andfieldvalues.Inaddition, the DBEcansupplyadjectivesandverbs,aswellassynonymsforwordsalreadyacquired(seeSection2.4).Associatedwitheverylexicalentryissyntacticandsemanticinformationforeach of itssenses.Syntacticinformationconsists of itsprimarycategory(e.g.,noun,verb,oradjective),subcategory(e.g.,count,unit,ormassfornouns;objecttypesforverbs),andmorphology.Semanticinformationdependson the syntacticcategory. The entryforeachnounincludes the sort(s)orindividual(s)in the conceptualschema(Section2.3.2)towhichthatnouncanrefer.Entriesforadjectivesandverbsinclude the conceptualpredicatetowhichtheyrefer,plusinformationabouthow the varioussyntacticconstituents of asentencemapontoarguments of the predicate.Scalaradjectives(e.g.,“high”)alsoincludeanindication of directionon the scale(plusorminus).2.3.2ConceptualSchema The conceptualschemacontainsinformationabout the objects,properties,andrelationsin the domain of the database.Itincludessets of individuals,predicates,constraintson the arguments of predicates,and the informationneededforcertainpragmaticprocessing. The informationalcontentissimilartothatcommonlyencodedinsemanticnetworks,but the apparatususedismoreeclectic. The conceptualschemaconsists of asorthierarchyanddescriptions of variousproperties of nonsortpredicates. The sorthierarchyrelatescertainmonadicjpredicatesthatplayaprimaryroleincategorizingindividuals.Thesearecalledsortpredicates(representedhereinitalicsasinPERSON).TEAMwasdesignedwithaconsiderableamount of thisconceptualinformationbuiltin.Figure3illustrates7Asnotedpreviously, the specificformdependsalsoongeneralsyntactic,semantic,andpragmaticrulesforEnglishthatareencodedin the variouscomponents of DIALOGIC.—16—...

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A quarterly bulletin of the IEEE computer society technical committee on Database engineering (VOL. 9) pptx

Danh mục: Cơ sở dữ liệu

... MESH,MESHisacomplexnetwork of pointers.Ateachstepin the search, the transformationperformedis the onewhichcarries the mostpromisethatitwilleventually,viasubsequenttransformations,leadto the optimalqueryevaluationplan. The crucialelementinthissearchstrategyis the promisecalculation,called the promiseevaluationfunction.Itmustinclude the currentqueryandplan,otherqueriesandplanswhichhavewerefoundearlierin the searchprocess,andinformationabout the transformationruleinvolved. The mostnaturalmeasureforpromiseis the costimprovement of the accessplans.3.Modularization of DBICodeInanextensibledatabasesystem,therearealwayssomepartsin the optimizer(andinothercomponentsaswell)thatcannotbeexpressedinarestricted,e.g.rule-basedlanguage.Thesepartsarebestwrittenin the DBI’simplementationlanguage.Asoftwaretoolisusedtocombine the rulesand the DBI’ssourcecode.Foreasyextensibility,itisveryimportanttoassist the DBIindividing the codeintomeaningful,independentmodules.Notonlyisamodularoptimizereasiertoimplement,weenvisionthisasanaidformaintainingadatabasemanagementsystemthatevolvesovertime.Someoptimizercomponentscanonlybedefinedafter the datamodelhasbeendefined(data-model-dependentcomponents),andhencemustbeprovidedby the DBI.Inthissection,wewillbrieflyreviewthesecomponents,andhowtheyarebrokenintomodules.Wegenerallyassociatetheseprocedureswithone of the conceptsthatwehaveintroducedearlier,namelyoperators,methods,andrules.3.1.Data-Model-DependentDataStructuresTherearetwotypes of data-model-dependentdatastructuresthatareimportantin the optimizationprocess. First, thereareargumentsforoperatorsandmethods.Second,inalmostallcasesitisdesirabletomaintainsomedictionaryinformationforintermediateresultsinaquerytree.Wetermsuchdictionaryinformationproperties of the intermediateresults.Sincedefiningthesedatastructuresispart of customizinganextensibledatabasesystem, the optimizationcomponent of suchasystemmusttreatthesestructuresas“blackboxes”.InEXODUS,wedefineanduseaproceduralinterfacetomaintainandqueryproperties.Furthermore,wedistinguishbetweenoperatorandmethodarguments,andbetweenoperator-dependentandmethod-dependentproperties.Asanexamplefromarelationalsystem,cardinalityandtuplewidthareoperator-dependentproperties,whereassortorderisamethod-dependentproperty.3.2.RulesandConditionsIn the EXODUSoptimizationconcept, the set of operators, the set of methods,transformationrules,andimplementationrulesare the centralcomponentsthat the DBIspecifiestoimplementanoptimizer. The rulesarenon-procedural;theyaregivenasequivalencelawsthat the generatortranslatesintocodetoperformtreetransfonnations.Each of theserulesshouldbeself-contained.Onlythenisitpossibletoexpand the rulesetsafelyas the datamodelevolves. The rulesexpressequivalence of querytrees.Treeexpressions,i.e.algebraicexpressions,embody the shape of atreeand the operatorsinit.Forsomerules,however,applicabilitydoesnotdependon the tree’sshapeand the operatorsalone.Forexample,sometransformationsmightonlybepossibleifanoperatorargumentsatisfiesacertaincondition.Sinceoperatorargumentsshouldbedefinedby the DBI,suchconditionscannotbeexpressedinadatamodelindependentform.Weallow the DBItoaugmentruleswithsourcecodetoinspect the operatorarguments, the datadictionary,etc.3.3.CostFunctionsAsmentionedearlier,processingcostoccursbyexecutingaparticularalgorithm. The costcalculationiscloselyrelatedto the processingmethodbeingexecuted.Hence,weassociatecostfunctionswith the methods,andcalculate the cost of aqueryexecutionplanas the sum of the costs of the methodsinvolved. The parameters of acostfunctionare the characteristics of the datastreamsservingasinputsinto the method,e.g. the number of dataobjectsineachinputdatastream,and the methodargument,e.g.apredicate.3.4.PropertyFunctions The characteristics of the datastreamwhichareneededasparametersto the costfunctionsaredatamodel-dependent.Thus,theymustbedefinedby the DBI.Weattachcharacteristics,whichwecallproperties,withboth the operatorsand the methods.Operators(andtheirarguments)determine the logicalproperties of anodeinaquerytree,e.g.cardinality.Aparticularalgorithmormethodchosendefinesphysicalproperties of an39 ... astobe(easonablyefficient.Inlogicqueriesitisexpectedthat the number of relationscaneasilyexceed10—15relations.InKBZ86],wepresentedaquadratictimealgorithmthatcomputes the optimalordering of conjunctivequerieswhen the queryisacyclic.Further,thisalgorithmwasextendedtoincludecyclicqueriesandothercostmodels.Moreover, the algorithmhasprovedtobeheuristicallyveryeffectiveforcyclicqueriesonce the minimumcostspanningtreeisusedas the treequeryforoptimizationV86].Anotherapproachtosearching the largesearchspaceistouseastochasticalgorithm.Intuitively, the minimumcostpermutationcanbefoundbypicking,randomly,a“large”number of permutationsfrom the searchspaceandchoosing the minimumcostpermutation.Obviously, the number of permutationsthatneedtobechosenapproaches the size of the searchspaceforareasonableassurance of obtaining the minimum.Thisnumberisclaimedtobemuchsmallerbyusingatechniquecalledsimulatedannealing1W87]andthistechniquecanbeusedin the optimization of conjunctivequeries.Insummary, the problem of enumerating the searchspaceisconsidered the majorproblemhere.3.2.NonrecursiveQueries:We first presentasimpleoptimizationalgorithmfor the executionspace{MP,PS,PP,PR}(i.e.,anyflatten/unflattentransformationisdisallowed),usingwhich the issuesarediscussed.Asin the case of conjunctivequeryoptimization,wepushselect/projectdownto the first operationonarelationandlimit the enumerationto{MP,PR}.Recallthat the processinggraphforanyexecution of anonrecursivequeryisanAND/ORtree. First consider the casewhenwematerialize the relationforeachpredicatein the rulebase.Aswedonotallow the flatten/unflattentransformation,wecanproceedasfollows:optimizealowestsubtreein the AND/ORtree.Thissubtreeisaconjunctivequery,asallchildreninthissubtreeareleaves(i.e.,baserelations),andwemayuse the exhaustivecasealgorithm of the previoussection.Afteroptimizing the subtree,wereplace the subtreebya“baserelation”andrepeatthisprocessuntil the treeisreducedtoasinglenode.Itiseasytoshowthatthisalgorithmexhausts the searchspace{PR}.Further,suchanalgorithmisreasonablyefficientifnumber of predicatesin the bodydoesnotexceed10—15.Inordertoexploitsidewaysinformationpassingbychoosingpipelinedexecutions,wemake the followingobservation.Becauseall the subtreeswerematerialized, the bindingpattern(i.e.,allargumentsunbound) of the head of anyrulewasuniquelydetermined.Consequently,wecouldoutlineabottom-upalgorithmusingthisuniquebindingforeachsubtree.Ifwedoallowpipelinedexecution,then the subtreemaybeboundindifferentways,dependingon the ordering of the siblings of the root of the subtree.Consequently, the subtreemaybeoptimizeddifferently.Observethat the number of bindingpatternsforapredicateispurelydependenton the number of arguments of thatpredicate.So the extensionto the abovebottom-upalgorithmistooptimizeeachsubtreeforallpossiblebindingsandtouse the costfor the appropriatebindingwhencomputing the cost of joiningthissubtreewithitssiblings. The maximumnumber of bindingsisequalto the cardinality of the powerset of the arguments.Inordertoavoidoptimizingasubtreewithabindingpatternthatmayneverbeused,atop-downalgorithmcanbedevised.Inanycase, the algorithmisexpectedtobereasonablyefficientforsmallnumbers of arguments,k,and of predicatesin the body,n.Whenkand/ornareverylarge,itmaynotbefeasibletousethisalgorithm.Weexpectthatkisunlikelytobelarge,buttheremayberulebasesthathavelargen.Itisthenpossibletouse the polynomialtimealgorithmor the stochasticalgorithmpresentedin the previoussection.Eventhoughwedonotexpectktobeverylarge,itwouldbecomfortingifwecanfindanapproximationforthiscasetoo.Thisremainsatopicforfurtherresearch.Insummary, the technique of pushingselect/projectinagreedywayforagivenordering(i.e.,asidewaysinformationpassing)canbe ... astobe(easonablyefficient.Inlogicqueriesitisexpectedthat the number of relationscaneasilyexceed10—15relations.InKBZ86],wepresentedaquadratictimealgorithmthatcomputes the optimalordering of conjunctivequerieswhen the queryisacyclic.Further,thisalgorithmwasextendedtoincludecyclicqueriesandothercostmodels.Moreover, the algorithmhasprovedtobeheuristicallyveryeffectiveforcyclicqueriesonce the minimumcostspanningtreeisusedas the treequeryforoptimizationV86].Anotherapproachtosearching the largesearchspaceistouseastochasticalgorithm.Intuitively, the minimumcostpermutationcanbefoundbypicking,randomly,a“large”number of permutationsfrom the searchspaceandchoosing the minimumcostpermutation.Obviously, the number of permutationsthatneedtobechosenapproaches the size of the searchspaceforareasonableassurance of obtaining the minimum.Thisnumberisclaimedtobemuchsmallerbyusingatechniquecalledsimulatedannealing1W87]andthistechniquecanbeusedin the optimization of conjunctivequeries.Insummary, the problem of enumerating the searchspaceisconsidered the majorproblemhere.3.2.NonrecursiveQueries:We first presentasimpleoptimizationalgorithmfor the executionspace{MP,PS,PP,PR}(i.e.,anyflatten/unflattentransformationisdisallowed),usingwhich the issuesarediscussed.Asin the case of conjunctivequeryoptimization,wepushselect/projectdownto the first operationonarelationandlimit the enumerationto{MP,PR}.Recallthat the processinggraphforanyexecution of anonrecursivequeryisanAND/ORtree. First consider the casewhenwematerialize the relationforeachpredicatein the rulebase.Aswedonotallow the flatten/unflattentransformation,wecanproceedasfollows:optimizealowestsubtreein the AND/ORtree.Thissubtreeisaconjunctivequery,asallchildreninthissubtreeareleaves(i.e.,baserelations),andwemayuse the exhaustivecasealgorithm of the previoussection.Afteroptimizing the subtree,wereplace the subtreebya“baserelation”andrepeatthisprocessuntil the treeisreducedtoasinglenode.Itiseasytoshowthatthisalgorithmexhausts the searchspace{PR}.Further,suchanalgorithmisreasonablyefficientifnumber of predicatesin the bodydoesnotexceed10—15.Inordertoexploitsidewaysinformationpassingbychoosingpipelinedexecutions,wemake the followingobservation.Becauseall the subtreeswerematerialized, the bindingpattern(i.e.,allargumentsunbound) of the head of anyrulewasuniquelydetermined.Consequently,wecouldoutlineabottom-upalgorithmusingthisuniquebindingforeachsubtree.Ifwedoallowpipelinedexecution,then the subtreemaybeboundindifferentways,dependingon the ordering of the siblings of the root of the subtree.Consequently, the subtreemaybeoptimizeddifferently.Observethat the number of bindingpatternsforapredicateispurelydependenton the number of arguments of thatpredicate.So the extensionto the abovebottom-upalgorithmistooptimizeeachsubtreeforallpossiblebindingsandtouse the costfor the appropriatebindingwhencomputing the cost of joiningthissubtreewithitssiblings. The maximumnumber of bindingsisequalto the cardinality of the powerset of the arguments.Inordertoavoidoptimizingasubtreewithabindingpatternthatmayneverbeused,atop-downalgorithmcanbedevised.Inanycase, the algorithmisexpectedtobereasonablyefficientforsmallnumbers of arguments,k,and of predicatesin the body,n.Whenkand/ornareverylarge,itmaynotbefeasibletousethisalgorithm.Weexpectthatkisunlikelytobelarge,buttheremayberulebasesthathavelargen.Itisthenpossibletouse the polynomialtimealgorithmor the stochasticalgorithmpresentedin the previoussection.Eventhoughwedonotexpectktobeverylarge,itwouldbecomfortingifwecanfindanapproximationforthiscasetoo.Thisremainsatopicforfurtherresearch.Insummary, the technique of pushingselect/projectinagreedywayforagivenordering(i.e.,asidewaysinformationpassing)canbe...

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Báo cáo toán học: " Decision making for cognitive radio equipment: analysis of the first 10 years of exploration" potx

Danh mục: Toán học

... view on the ﬁrst 10 years of CR. Morespeciﬁcally of the different challenges faced by the CR decision making community and the suggestedsolution to answer them. We state that most of these decision ... pulls. In the OSA framework, the SU is modeledas the gambler while the frequency bands represent the levers. The gambler faces at each trial a trade-offbetween pulling the lever with the highest ... capture from the environment may contain errors. Then wedescribe the potential consequence of such errors on the performance of class of algorithms previouslyclassiﬁed.Due to their lack of ﬂexibility,...

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báo cáo hóa học: " On the solvability conditions of the first boundary value problem for a system of elliptic equations that strongly degenerate at a point" pdf

Danh mục: Hóa học - Dầu khí

... identity˜qn1j(r) ≡0because of the continuity of the function˜qn1jon (0, R). In such a case, the elements of the second row of matrix˜Qnsatisfy the equationln(˜qn2j)=0. For the samereason ... coefficientsBi(x) have the main influence to the asympto tic of the solutions of system (1), then the last requirement is dispensable [8,9]). Therefore, it is important to consider the casewhere C(0) ... statement of the problems The first results in the area of boundary value problems for an elliptic equation withdegeneracy at an inner point of the considereddomainareobtainedin[1].Inthatstudy, the...