晶体CIF文件语法中英对照.docx

晶体CIF文件语法中英对照.docx

《晶体CIF文件语法中英对照.docx》由会员分享，可在线阅读，更多相关《晶体CIF文件语法中英对照.docx（37页珍藏版）》请在冰点文库上搜索。

晶体CIF文件语法中英对照

Syntax

Version1.1Workingspecification

∙Introduction

∙Definitionofterms

∙Filesyntax

oGeneralfeatures

oCharacterset

oWhitespace

oEnd-of-lineconventions

oCasesensitivity

oImplementationrestrictions

▪Maximumlinelengthandcharacterset

▪Maximumdataname,blockcodeandframecodelengths

▪Single-levelloopconstructions

▪Non-expansionofsaveframereferences

▪Exclusionofglobal_blocks

∙Versionidentification

∙AppendixA:

AformalgrammarforCIF

oSummary

oExplanationoftheformalsyntax

oLexicaltokens

oCIFgrammar

∙References

Introduction

1.ThisdocumentdescribesthefullsyntaxoftheCrystallographicInformationFile（CIF）.

Definitionofterms

2.ThefollowingtermsareusedintheCIFspecificationdocumentswiththespecificmeaningsindicatedhere.

∙2.1.ACIFisafileconformingtothespecificationhereinstated,containingeitherinformationonacrystallographicexperimentoritsresults（orsimilarscientificcontent）;ordescriptionsofthedataidentifiersinsuchafile.

∙2.2.Adatafileisunderstoodtoconveyinformationrelatingtoacrystallographicexperiment.

∙2.3.Adictionaryfileisunderstoodtocontaininformationaboutthedataitemsinoneormoredatafilesasidentifiedbytheirdatanames.

∙2.4.Adatanameisacase-insensitiveidentifier（astringofcharactersbeginningwithanunderscorecharacter）ofthecontentofanassociateddatavalue.

∙2.5.Adatavalueisastringofcharactersrepresentingaparticularitemofinformation.Itmayrepresentasinglenumericalvalue;aletter,wordorphrase;extendeddiscursivetext;orinprincipleanycoherentunitofdatasuchasanimage,audiocliporvirtual-realityobject.

∙2.6.Adataitemisaspecificpieceofinformationdefinedbyadatanameandanassociateddatavalue.

∙2.7.Atagisunderstoodinthisdocumenttobeasynonymfordataname.

∙2.8.Adatablockisthehighest-levelcomponentofaCIF,containingdataitemsorsaveframes.Adatablockisidentifiedbyadatablockheader,whichisanisolatedcharacterstring（thatis,boundedbywhitespaceandnotformingpartofadatavalue）beginningwiththecase-insensitivereservedcharactersdata_.

∙2.9.Ablockcodeisthevariablepartofadatablockheader,e.g.thestringfoointheheaderdata_foo.

∙2.10.Asaveframeisapartitionedcollectionofdataitemswithinadatablock,startedbyasaveframeheader,whichisanisolatedcharacterstringbeginningwiththecase-insensitivereservedcharacterssave_,andterminatedwithanisolatedcharacterstringcontainingonlythecase-insensitivereservedcharacterssave_.

∙2.11.Aframecodeisthevariablepartofasaveframeheader,e.g.thestringfoointheheadersave_foo.

Filesyntax

3.ThesyntaxofCIFisapropersubsetofthesyntaxofSTARFilesasdescribedbyHall（1991）andHall&Spadaccini（1994）.ThegeneralstructureisdescribedbelowundertheheadingGeneralfeatures,andanumberofsubsectionslistspecificrestrictionstotheSTARsyntaxthatareinforcewithinCIF.AformallanguagegrammarusingcomputersciencenotationisincludedasAppendixA.

Generalfeatures

4.ACIFconsistsofdatanames（tags）andassociatedvaluesorganizedintodatablocks.Adatablockmaycontaindataitems（associateddatanamesanddatavalues）and/oritmaycontainsaveframes.

5.Saveframesmayonlybeusedindictionaryfiles.

Implementationnote:

Atapurelysyntacticlevelthereisnowaytodistinguishbetweendictionaryanddatafiles.（Itisalsotobenotedthatnotalldictionaryfilescontainsaveframes.）Afullyvalidatingparsermustthereforebeabletodetectthestartandterminationofsaveframes,theuniquenessoftheframecodewithinadatablock,andtheuniquenessofdatanameswithinaframecode.Itishoweverlegitimateforanapplication-basedparserdesignedtohandleonlythecontentsofdatafilestoconsiderthepresenceofasaveframeasanerror.

6.Adatablockbeginswiththereservedcase-insensitivestringdata_followedimmediatelybythenameofthedatablock,formingadatablockheader.Asaveframehasasimilarstructuretoadatablock,butmaynotitselfcontainfurthersaveframes.Asaveframebeginswiththereservedcase-insensitivestringsave_followedimmediatelybythenameofthesaveframe,formingasaveframeheader.Unlikeadatablock,asaveframealsohasamarkerfortheendoftheframeintheformofarepetitionofthereservedcase-insensitivewordsave_,thistimewithoutthenameoftheframe.Saveframesmaynotnest.WithinasingleCIF,notwodatablocksmayhavethesamename;withinasingledatablocknotwosaveframesmayhavethesamename,althoughasaveframemayhavethesamenameasadatablockinthesameCIF.

7.Agivendataname（tag）（see2.4and2.7）mayappearnomorethanonceinagivendatablockorsaveframe.Atagmaybefollowedbyasinglevalue,oralistofoneormoretagsmaybemarkedbytheprecedingreservedcase-insensitivewordloop_astheheadingsofthecolumnsofatableofvalues.Whitespaceisusedtoseparateadatablockorsaveframeheaderfromthecontentsofthedatablockorsaveframe,andtoseparatetags,valuesandthereservedwordloop_.Dataitems（tagsalongwiththeirassociatedvalues）thatarenotpresentedinatableofvaluesmayberelocatedalongwiththeirvalueswithinthesamedatablockorsaveframewithoutchangingthemeaningofthedatablockorsaveframe.Completetablesofvalues（thetablecolumnheadingsalongwithallcolumnsofdata）mayberelocatedwithinthesamedatablockorsaveframewithoutchangingthemeaningofthedatablockorsaveframe.Withinatableofvalues,eachtagmayberelocatedalongwithitsassociatedcolumnofvalueswithinthesametableofvalueswithoutchangingthemeaningofthetableofvalues.Ingeneraleachrowofatableofvaluesmayalsoberelocatedwithinthesametableofvalueswithoutchangingthemeaningofthetableofvalues.Combiningtablesofvaluesorbreakinguptablesofvalueswouldchangethemeanings,andislikelytoviolatetherulesforconstructingsuchtablesofvalues.

8.Thecase-insensitivewordglobal_,usedinSTARFilestointroduceagroupofdatavalueswithascopeextendingtotheendofthefile,isanadditionalreservedwordinCIF（thatis,itmaynotbeusedastheunquotedvalueofanydataitem）.

9.Ifadatavalue（see2.5）containswhitespaceorbeginswithacharacterstringreservedforaspecialpurpose,itmustbedelimitedbyoneofseveralsetsofspecialcharacterstrings（thechoiceofwhichisconstrainedifthedatavaluecontainscharactersinterpretableasmarkinganewlineoftextaccordingtothediscussioninthefollowingparagraphs）.Suchadatavaluewillbeindicatedbythetermnon-simpledatavalue.

10.Asimpledatavalue（i.e.onewhichdoesnotcontainwhitespaceorbeginwithaspecialcharacterstring）mayoptionallybedelimitedbyanyofthesamesetofdelimitingcharacterstrings,exceptfordatavaluesthataretobeinterpretedasnumbers.

11.Thespecialcharacterstringsinthiscontextarelistedinthefollowingtable.Theterm"non-simpledatavalues"inthistablereferstodatavaluesbeginningwiththesespecialcharacterstrings.

characterorstring

role

_（underscore）

identifiesdataname

#

identifiescomment

$

identifiessaveframepointer

'

delimitsnon-simpledatavalues

"

delimitsnon-simpledatavalues

[

reservedopeningdelimiterfornon-simpledatavalues（seeparagraph19）

]

reservedclosingdelimiterfornon-simpledatavalues（seeparagraph19）

;atbeginningoflineoftext

delimitsnon-simpledatavalues

data_

identifiesdatablockheader（case-insensitive）

save_

identifiessaveframeheaderorterminator（case-insensitive）

Inadditionthefollowingcase-insensitivereservedwordsmaynotoccurasunquoteddatavalues.

reservedword

role

loop_

identifiesloopedlistofdata

stop_

reservedSTARwordterminatingnestedloopsorloopheaders

global_

reservedasSTARglobalblockheader

12.ThecompletesyntacticdescriptionofanumericdatavalueisincludedinAppendixA（paragraph57）undertheproduction（i.e.ruleforconstructingapartofthelanguage）.

13.ThebaseCIFspecificationdistinguishesbetweencharacterandnumericvalues（seeparagraph15ofthedocumentCommonsemanticfeatures）.ParticularCIFapplicationsmaymakemorefinely-graineddistinctionswithinthesetypes.Theparagraphsimmediatelyabovehavethecorollarythatadatavaluesuchas12thatappearswithinaCIFmaybequoted（e.g.'12'）if,andonlyifitistobeinterpretedandstoredincomputermemoryasacharacterstringandnotanumericvalue.Forexample'12'mightlegitimatelyappearasalabelforanatomicsite,whereanotheralphabeticoralphanumericstringsuchas'C12'isalsoacceptable;butitmaynotlegitimatelybeusedtorepresentanintegerquantitytwelve.

14.Matchingsingleordoublequotecharacters（'or"）maybeusedtoboundastringrepresentinganon-simpledatavalueprovidedthestringdoesnotextendovermorethanoneline.

15.Becausedatavaluesareinvariablyseparatedfromothertokensinthefilebywhitespace,suchaquote-delimitedcharacterstringmaycontaininstancesofthecharacterusedtodelimitthestringprovidedtheyarenotfollowedbywhitespace.Forexample,thedataitem

_example'adog'slife'

islegal;thedatavalueisadog'slife.

16.Notethatconstructssuchas'anembedded\'quote'donotbehaveasinthecaseofmanycurrentprogramminglanguages;i.e.thebackslashcharacterinthiscontextdoesnotescapethespecialmeaningofthedelimitercharacter.Abackslashprecedingtheapostropheordouble-quote