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Chapter 3. XForms User Interface Controls

Chapter 3. XForms User Interface Controls

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controlscanberenderedusingplatform-specificwidgetsto

enablerichdataentry.

Traditionaluserinterfacesprovideavarietyofwidgetsthat

enablecontrolleduserinput,forexample,pull-downliststhat

allowtheusertopickfromagivensetofchoices.XForms

providesthisfunctionalityviacontrols select and select1 ,

describedinSection3.4.Thesecontrolsareusefulwhentheset

ofvaluesthattheusercanprovideisconstrainedinsome

manner,forexample,pickingastatefromalistofstates.

XFormsselectcontrolsprovideaflexibleyetdevice-independent

meansofcreatingsuchuserinterfaces.

Thenotionofselectingfromasetofavailablevaluescanbe

furtherrefinedwhentheunderlyingsetofvaluesisordered.

Thismanifestsitselfintraditionaluserinterfacesintheformof

widgets,suchasslidersandspindials,thatmakethestructure

ofthespaceofavailablevaluesapparenttotheuser.XForms

includescontrol range ,describedinSection3.5,thatcanbe

usedforthispurpose.

Control upload ,describedinSection3.6,providesthefamiliar

fileuploadfeatureofHTMLforms;atthesametime,itis

designedtobeusableondevicesthatdonotcontainafile

systembutneedtouploaddatatoaWebserver,forexample,

digitalcameras.

Finally,wedescribeXFormscontrolsthatenabletheuserto

invokespecificcommands.Traditionalvisualinterfacesprovide

agenericbuttonwidgetthatisusedtoinvokeagiven

command;control trigger ,describedinSection3.7,

generalizesthisideabyenablingtheXFormsauthortospecify

oneormoreactionhandlerstobeinvokedwhenthetriggeris

activated.Thefamiliarsubmitcontrolusedtosubmitdatafrom

aWebformisenabledviaXFormsaction send .Control

submit ,describedinSection3.8,isthusaspecialcaseof

control trigger thatinvokesaction send .Weconcludethe

chapterwithasummaryofthevarioususerinterfacecontrolsin



Section3.9.



Chapter4.CreatingComplexUser

Interfaces

Complexuserinterfacescanbecreatedbyaggregatinguser

interfacecontrolsdescribedinChapter3.Webeginthischapter

withanoverviewoftheXFormsaggregationconstructs.Likethe

userinterfacecontrols,aggregationconstructsaredesignedto

encourageintent-basedauthoringoftheuserinteraction.The

goalistocapturesufficientinformationabouttheunderlying

man-machineconversationandtherebydeliverasatisfactory

end-userexperienceonavarietyofmodalitiesanddevices.

Theneedtorefactorauserinterfaceisthefirstrequirement

thatariseswhenoneattemptstodeliveragivenuser

interactiontoavarietyofend-userdevices.Asanexample,a

userinterfaceauthoredforalargedisplayoftenneedstobe

splitintoseveralscreens(oralogicaldeckofcards)when

renderedonacellphone.Effectiverefactoringofuserinterfaces

isbestachievediftheinformationneededforrefactoringis

capturedatauthoringtime.Aggregationconstruct group

describedinSection4.1wasspecificallyintroducedintoXForms

toplaythisrole.

Efficientnavigationamongthepartsofacomplexuserinterface

canbeamajorfactorindeterminingoverallusability.Thisis

especiallytruewhenacomplexuserinterfacemaybe

refactoredintoanumberoflogicaltransactionalunits.Asthe

man-machineconversationgetsmorecomplex,theabilityto

introducedynamicconstructsthatenabletheconditional

activationofrelevantportionsoftheuserinterfaceleadto

efficientnavigationandtaskcompletion.Aggregationconstruct

switch describedinSection4.2canbeusedtoauthor

dynamicuserinterfacesthatrespondtouserinteractionevents

byappropriatelyrevealingspecificportionsofauserinterface.



Electronicforms(incontrasttopaperforms)arecharacterized

bytheirabilitytoadapttotheuser'sactionsandgrowas

necessary.Thus,ashoppingapplicationmightstartoffby

displayingashoppingcartwithspaceforasmallnumberof

entries.However,astheuserproceedstoadditemstothe

shoppingcart,theinterfaceadaptsitselfbycreatingadditional

rowsintheshoppingcartinterface.Thisformofdynamismin

XFormsisenabledbyaggregationconstruct repeat described

inSection4.3.

Construct repeat canbenested,andthisabilitycanbeused

toadvantageincreatinguserinterfacesformanipulating

complexhierarchicalstructures.Associatedeventhandlers

insert and delete canbeusedinconjunctionwithrepeating

constructscreatedviaelement repeat toeditandupdate

complexhierarchicalstructuresinteractively.

WeconcludethischapterinSection4.4withastep-by-step

descriptionofacomplexuserinterfacethatusesthevarious

userinterfacecontrolsandaggregationconstructs.



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