Hermes: A Tutorial and Reference Manual - Researcher - IBM
Hermes: A Tutorial and Reference Manual - Researcher - IBM
Hermes: A Tutorial and Reference Manual - Researcher - IBM
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thecompilertoforgetthattheprogramvalueP.Bhasbeenchecked,becauseitisbeinginsertedintoatablecontainingprogramvalueswhicever,thereisan\extra"attribute|checked(P.B).Thecoerciondrop<br />
9010.7.HowtoApplytheTypestateRules areinitializedbutnotchecked.Whenthevalueisremovedfromthetable,itwillbeassumedtobeunchecked.Thetypestateisnowfinit(I),<br />
arepresentinthetypestate,thereisno\missingattribute"error.How-<br />
init(R),init(P),init(P.A),init(P.B)g. iedbytheoperation.Fromthisrule,weinferthatP<strong>and</strong>Rmustnotbe constant.Iftheyare,thecompileragsanerror. Therulesvar(table)<strong>and</strong>var(element)tellsuswhichoper<strong>and</strong>saremod-<br />
checked(P.B)isinsertedtodropthechecked(P.B)attribute.Thiscauses<br />
TheDepletionexceptionwasdeterminedfromtheexceptionlist,because ofexceptionswhichcouldberaised. everyinsertoperationcanraisethisexception.TheDuplicateKeywas tableRwasdenedaskeyed,<strong>and</strong>ifso,toincludeDuplicateKeyintheset calreasons,itisincludedwiththepreconditionrules<strong>and</strong>evaluatedwhen preconditionsareevaluated.Theeectoftheruleistocheckwhetherthe derivedbyevaluatingthepredicateduplicatekey(table),becauseonly Thepossibleoutcomesofinsertare:normal,Depletion,<strong>and</strong>DuplicateKey. The\rule"duplicatekey(table)isnotapreconditionrule.Fortechni-<br />
insertionsintokeyedtablescanraisethisexception. rules.Forinsert,theserulesare: Thepostconditionfornormalexitisdeterminedbythepostcondition<br />
Therulekillconstraints(table)dropsanyconstraintattributesofthe executed.Sothetypestateassociatedwiththetwoexceptionoutcomes isalsofinit(I),init(R),init(P),init(P.A),init(P.B)g.Forthis reason,exceptionpostconditionsarenotshowninthetable. changedvalue<strong>and</strong>anunchangedtypestate|asiftheoperationhadnot tributesofP<strong>and</strong>itscomponents|namelyfinit(P),init(P.A),init(P.B)g. Therulemakeuninit(element)makesPuninitializedbydroppingallat-<br />
(makeuninit(element),killconstraints(table))<br />
table|therewerenone.ThepostconditionfunctionsareexplainedinsectionB.5.<br />
Exceptforthecallstatement,allexceptionoutcomesproduceanun-<br />
Theinitialtypestateisoneinwhichtheinitializationportisinitialized<strong>and</strong> init(R)g. 10.8TheCheckingAlgorithm noothertypestateattributesarepresent. Sothetypestateassociatedwithnormalcompletionofinsertis:finit(I),<br />
quired<strong>and</strong>forbiddenattributespriortotheoperation,<strong>and</strong>theadded<strong>and</strong> Ateachstatement,therulesinthetableareusedtodeterminethere-
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