Modelling Web Navigation by Statechart(9)

UML,OOP,面向对象

Statechart mainWin

Statechart adsWin

Figure16.ModelingMultipleWindowstionoftheevent.TheyarenotmodeledasorthogonalANDbecausenotallofthewindowswillco-existallofthetime,eitherbydesignorbyusermanuallycreatingorclosingnewwindows,sotherearetimeswhenthesystemisnotinallofthesub-statessimultaneously.

Synchronizationbetweenwindowsisstillpossiblebythesamemechanismasinframes.Eventscanbedirectedtoadifferentwindowthanthegeneratingone.Modelingthissynchronizationisdoneby“broadening”theeffectofbroadcastofeventstoeveryStatechartinthemodel.4.2.5DynamicContent

Dynamicwebpagesgiverisetodif cultiesinwebnaviga-tionmodeling,asnotallstatesareknowninadvance(asofstaticwebpages)andthesizeofthesetofpossiblestatecanbeverylargeevenifknown.Thesetofpossiblenavigationpathsofthesedynamicpagescanalsobedynamic.Thefollowingsdiscussthemodelingmethodofthesedynamicrelationships.

ServerSide

Tomodelserversidedynamiccontent,itisimpossibletolistouteverypossibleresultpageasaseparatestateinthemodelbecauseofthesheerquantity.parameterized-ORisusedheretosolvetheproblem.Allpagesgeneratedfromthesametemplateareconsideredtobeasingleparameter-izedstate(result.html-Figure17).Aneweventsm(target,param)isde nedastheactionofsendingoutapagerequesttotargetwithparametersparam.Bothtargetandparamareprimitivevariablesinthestatechartmodel.Therewillbeasetofpossiblereturnpagesandtheoneactuallyreturnedwillbeselectedorgeneratedusingparambyserversideprogramsatruntime.

Hyperlinksleadingoutoftheparameterizedstate

Figure17.ServerSideDynamicPages

havetwotypes.Forthehyperlinksthatarepresentinallparameterizedpages,theparameterizedsetofwebpagecanbetreatedasasinglestatewiththetransitionleadingoutnormallyasshownbytheeventjp(search,pos)fromresult.html.Forallotherhyperlinks,iftheirquantityistoolargeorcannotbepredetermined,adisjunctionofalltheselowerleveleventsneedtobede nedtoconnecttoaselectconnective.InFigure17,theeventresult.jpfromresult.htmlisde nedasthedisjunctionofeventssm(order,p)andjp(outOfStock,pos),whichinturnrepre-sentsjumpingtotheorderpageoftheselectedproductpandaOutofStockpagerespectively.ClientSide

Wearenotconcernedwiththestatechangeinclientsidescriptsandprogramsthatdonothaveanyimplica-tiononnavigation.Sotheyaremodeledasanyotherex-ecutableobjectthatmaintainstheirownstatebyState-chart[4].Outwebnavigationmodelwillnotcovermod-elingofexecutableobjects.TheStatechartobtainedfromexecutableobjectmodelingisorthogonalAND-edwiththewebpagestatewhichhoststhescriptorprogramtoformthenewcomposedstaterepresentationofthepage.Be-causethescriptsandprogramsareinitializedanddestroyedwiththehostingwebpage,thesystemwillbeinallofthesesub-statesconcurrently.Thisissimilartothemodelingofframes,butsub-statesofaclientsideprogramarenotwebpagestatesandtransitionsarenotfromhyperlinkactivation.