Addison Wesley XML And Java Developing Web Applications May 1999 ISBN 0201485435

8.6EvolutionofWebApplications
ThepotentialofXML-enabledWebapplicationscanbeillustratedbythe
verysimpleTravelPlanningapplicationthatwedevelopedinthischapter.
Airlineandhotelcompanieshaveinvestedalottomaketheirexisting
backendsystems(typicallybasedonLotusNotes,SAP,andsoon)
accessiblefromWebbrowsers.Thishasbeenatremendoussuccess,
nowexertinggreaterreachtoendusersallovertheworld.However,that
reachislimitedtobrowsers(andthustohumanusers)becauseHTMLis
goodonlyfordisplayingonthescreen.Forexample,atravelagentwho
wantstoputtheflightinformationinaspreadsheettocombineitwith
otherinformationforacustomermustmanuallycutandpasteindividual
piecesofinformationbetweentheWebbrowserandthespreadsheet
application.
8.6.1BrowserClients
Figure8.10depictsapossiblescenariooftheevolutionofaWebsite
poweredbyXML.ExistingWebapplicationsaretypicallydesignedto
generateHTMLpagesdirectlyfromadatabase.Thefirststeptoestablish
anXML-enabledWebsiteistogeneratealogicalandpresentationneutralrepresentationinXML/DOM,whichistobeconvertedintoHTML,
asshownincase(1)inFigure8.10.Thiscoversallofthebrowserbasedclients.
Figure8.10XML-poweredWebsite


8.6.2officeClients
Thesecondstepistoconvertthepresentation-neutralrepresentationinto
aformatthatissupportedbyofficeproducts.Forexample,ifthetravel
agentreceivestheflightinrormationinXMLthatiscompatiablewithoffice
products,thatinformationcanbefedintoaspreadsheet,thereby
eliminatingtediouscut-and-pasteoperations.Thisisshownincase(2)in
Figure8.10.MicrosoftandLotusarequicklymovingtowardssupporting
XMLintheirofficeproducts.Forexample,Lotuse-SuiteisalreadyXMLenabled,soyoucancreateanXMLdocumentthatisdirectlyloadableto
ane-Suitespreadsheet.

8.6.3IntegratedB2BApplications
Asthethirdstep,thetravelagencycanconnecttheXML-enabledairline
Websitetoitsbackendsystem(suchasSAP),thereybyallowingagents
toautomaticallychecktheflightavailabilityandtoissueorders.Thisis
shownincase(3)inFigure8.10.Inthisway,theXML-enabledWebsite
canbeintegratedintotheagency'senterprisesystemasoneofits
components.
AllofthesetransactionsaremadeontheInternetusingSSL,so
maximumsecurityismaintained,withnoneedforanexpensiveleased
line(VAN).Inaddition,digitalsignaturesbuildtrustamongbusiness
partners.


WebelievemanyWebsiteswillbeincreasinglyusedascomponenetsof
amore-or-lesssimilararchitectureinthenearfuture.thetechnologies
describedinthisbook-XML,Java,XMLprocessors,LMXprocessor,
servlets,SQLX,SSL,digitalsignatures,andJavabeans_areessentialfor
realizingthecomingworldofWebapplications.