6FutureDirectionsThisthesishaspresentedtwoprototypesthatwereimplementedforcomposingcomplexdocumentcontent,oneprototypeforgraphicalstyleandtheotherfortableformattingwithgridsandconstraints.Theseexperimentsledtomanyimplementationissuesandseveralnewresearchproblems.TheimplementationissuesarosefromadesiretoprovideintegratedandinteractiveillustrationandtabularcompositiontoolsintheTiogaandCedarenvironmentsatXeroxPARC.Theresearchproblemsfollowfromadesiretounifythetwoapproachesintothesamedocumentmodelandtoextendtherangeoffunctionalityinbothapproaches.Thischapteroutlinessomeofthesefutureproblemsandissues,inparticularacomprehensivedocumentframework,interactiveuserinterfacesfortheprototypes,variousproblemswithgraphicalstyleandtableformatting,andaproposalforconsideringrule-basedexpertsystemsupportforproblemsindocumentcomposition.6.1DocumentModelThedocumentmodelhasbeenacommonthreadthroughthetwoprototypesforgraphicalstyleandtableformatting.Thisexperienceshouldbegeneralizedintoadocumentmodelthatcanintegratearbitraryclassesofdocumentcontentbymorerigorouslydefiningtheobjectinterfacefortheeditorandtheformatter.Aninteractiveeditorforsuchadocumentmodelwouldcoordinatevariousspecialpurposeeditorsforeachclassofdocumentcontent6-1 p\dg Wng g>; #q;o"o% -1"5 ?9ggL#)R,46=AD75go #^'t*38 B D5g !s$*0-4+