DESIGN OF A COLLABORATIVE SYSTEM

Transcription

1 DESIGN OF A COLLABORATIVE SYSTEM Minjun Wang EECS Dpartmnt, Syracus Univrsity, U.S.A Community Grid Laboratory, Indiana Univrsity, U.S.A 501 N Morton, Suit 222, Bloomington IN 47404, U.S.A minwang@indiana.du Goffry C. Fox Community Grid Laboratory, Computr Scinc Dpartmnt, School of Informatics and Physics Dpartmnt, Indiana Univrsity, U.S.A gcf@indiana.du Abstract In this papr w introduc th dsign of a nw collaborativ systm in distanc ducation, -Larning and onlin confrncing collaborativ Imprss applications. Imprss is a prsntation application in Opn Offic/Star Offic; it has similar functionality as Microsoft PowrPoint. Making Imprss collaborativ across computrs is usful in -Larning, wb confrnc and distanc ducation. W hav dvlopd collaborativ Imprss applications which mak us of th functions of Imprss, and collaborat btwn th Mastr and Participating clints so that thy shar th sam prsntation slid display. W us a common mssag brokr, Narada Mssag Brokr, as th undrlying mssaging nvironmnt to communicat mssags btwn th clints in a sssion. W raliz th shard vnt ida in th collaboration. It uss vnt mssags in th controlling of a prsntation procss. Compard to shard display, th short txt mssags sav grat bandwidth ovr th Intrnt. This ralization is fast and fficint. Shard vnt modl should b a grat paradigm in collaboration. Ky Words Collaborativ Systm, Opn Offic, Shard Evnt. 1. Introduction Opn Offic [1] is an opn sourc offic suit; it has similar functionality as Microsoft Offic suit. Bcaus it is fr downloadabl, and vry on has an opportunity to dvlop and contribut to th rsourc using a broad rang of programming languags and protocols, it has th faturs such as availability, usability, xtnsibility, popularity, and vrsatility. It is popl s common proprty and wisdom. Imprss is a prsntation application in Opn Offic/Star Offic; it has similar functionality as Microsoft PowrPoint. Making Imprss collaborativ across computrs is usful in -Larning, wb confrnc and distanc ducation. W hav dvlopd collaborativ Imprss applications which mak us of th functions of Opn Offic/Star Offic, and collaborat btwn th Mastr and Participating clints so that thy shar th sam prsntation slid display. W us a common mssag brokr, Narada Mssag Brokr [2, 3], as th undrlying mssaging nvironmnt [4] to communicat mssags btwn th clints in a sssion. W raliz th shard vnt ida in collaboration [5, 6]. It uss vnt mssags in th controlling of a prsntation procss. Compard to shard display, th short txt mssags sav grat bandwidth ovr th Intrnt. This ralization is fast and fficint. Shard vnt modl should b a grat paradigm in collaboration. This ralization of collaborativ Imprss applications implis a complmntary ffort to and also a furthr rsarch ara in Opn Offic/Star Offic. 2. Shard Evnt Modl A commonly usd modl in collaboration is Shard Display. In this modl, som amount of scrn imag in a format (.g. bitmap) is snt ovr th ntworks btwn th collaborating computrs ach tim whn th imag of th scrn is changd, ithr partially or totally. Th Rmot Dsktop Connction of Microsoft Windows XP and VNC (Virtual Ntwork Computing) [7] ar using this modl. It is appropriat in situations spcially whr th scrn output is random, lik onlin mting, discussion, sharing data (txt, graph, imag, tc.,) or impromptu prsntations using som softwar. Th disadvantags of Shard Display includ: It consums big bandwidth of th ntworks bcaus of th imag transfrring. Thus it is rlativly slow and th latncy is big.

2 Th fling of using it is not smooth. Th waiting tim dpnds on th amount of imag of a scrn that nds to updat. Th worst cas is whn th imag changs abruptly, say, th whol scrn. Lt s xamin a cas of using prsntation fils in collaboration, such as Microsoft PowrPoint (.ppt) or Opn Offic/Star Offic Imprss (.sxi) fils. Each slid in a prsntation fil is diffrnt and th contnt of a whol scrn nds to updat. In this cas, th disadvantags of Shard Display bhav to th worst. To solv this problm, a comptnt collaboration modl is mant to tak plac and play an important rol. W bliv a lightwight modl, Shard Evnt Modl, will work fficintly and gracfully. Th ida is to catch vnt mssags in th driving sid (lt s call it Mastr Clint) of collaboration during a prsntation sssion, snd thm through common mssag brokrs to th othr accpting sid (Participating Clints or Participants), and rndr th slid displays ovr thr. Th vnt mssags ar short txt strings, as Prsntation Opn, Slid Chang, tc. Th prsntation fils ar dployd or downloadd to sam dirctoris on th hosts of both th Mastr and Participating clints bfor a sssion bgins. This way, th collaborativ applications can locat, opn and navigat through thm. This modl ovrcoms th disadvantags of Shard Display, and thrfor has ths advantags: It is fast and fficint, bcaus th small txt string mssags gratly rduc th ntwork traffic, and bcaus it maks full us of th computing powr of both sids. It givs consistnt and smooth flings of prsntations. Th siz of th mssags ar small and approximatly qual, so th tim for transfrring thm should rmain in a rlativly constant rang, just as mntiond in th papr Th Rul of th Milliscond. [8] At th sam tim, bcaus this modl maks us of modrn common mssag brokrs, it shars th advantags of th brokrs such as tolranc and quality of srvic. It also contributs to Pr-to-Pr Grids computing [9, 10, and 11]. Collaboration lik wb confrnc, distanc ducation and -larning is a trnd in today s information rvolution, and th usag of prsntation fils accounts for a considrabl proportion in all th visual aids. So, Shard Evnt modl is playing and will play an important rol and show its powr. 3. Collaboration Structur In th collaborativ Imprss applications, on typ is of Mastr clint, and th othr is of Participating clint, or Participant. Both of th clint typs cooprat with a common mssag brokr, Narada Mssag Brokr, as th undrlying communication nvironmnt to communicat mssags btwn th clints in a sssion. Th mastr clint lcturs and broadcasts its vnt mssags to all participating clints. Th applications mak us of th functions of Opn Offic/Star Offic, and collaborat btwn th Mastr and Participant clints so that thy shar th sam prsntation slid display. On th hosts of both th mastr and th participating clints, on should hav installd Opn Offic/Star Offic suit or just th Imprss application, and should dploy or download bforhand copis of prsntation fils to b in a lctur. Th Imprss prsntation fils ar dployd in consistnt dirctoris btwn th hosts of th mastr and th participating clints. Thus, th structur maks it possibl to collaborat btwn th clints by communicating only txt mssags. Th mastr clint capturs vnts lik fil opnd, slid changd during a sssion of a lctur, translats thm into txt mssags and snds th mssags to th participating clints through Narada mssag brokr. Th participating clints thn rndr th show of th lctur according to th dirctions of th rcivd mssags. This way, thy work synchronously in collaboration. This is illustratd in Figur 1. NaradaBrokring Mssag Srvic N Mastr Clint Figur 1. Th collaboration btwn th Mastr clint and th Participating clints via th NaradaBrokring Mssag Srvic 4. Nw Concpt for Collaboration Som faturs in Opn Offic/Star Offic ar mant to b lgant for univrsal programming and th Wb. Thy includ Univrsal Ntwork Objct (UNO) tchnology, divrs programming nvironmnt, fin-graind Application Programming Intrfacs (API), and Fram- Controllr-Modl Paradigm. Thy form a nw concpt for modrn programming, and global Collaboration [12]. 4.1 Univrsal Ntwork Objct Participating Clints UNO is a componnt tchnology that is dsignd for univrsal programming and application. Componnts in UNO can intract with ach othr across programming

3 languags, componnt tchnologis, computr platforms, and ntworks. UNO works with programming languags such as C++, Java, Java Script, Visual Basic, VBScript, and Dlphi. UNO is th bas componnt tchnology for Opn Offic/Star Offic; it can also cooprat with othr componnt tchnologis lik Java Bans and Microsoft COM/DCOM [13]. UNO is availabl on UNIX, Linux and Windows platforms, thus has th faturs of availability and popularity. UNO maks it possibl that componnts ar abl to collaborat through ntworks. In a word, just as its nam implis, UNO nabls objcts to function wll across ntworks, and maks univrsal programming and application of objcts a rality. Through UNO tchnology, application programs connct to local or rmot instancs of Opn Offic/Star Offic from C++, Java, or COM/DCOM. Th programs thn accss th functionality of th instancs using thir APIs, control and automat th procss, ithr squntially or intractivly. Th purpos of UNO is to trat applications/componnts as rusabl objcts, which ar accssibl univrsally through th undrlying infrastructur ntworks, as long as thos objcts ar cooprativ by providing programming intrfacs, typ libraris, tc. Th APIs of Opn Offic provid comprhnsiv spcification of its programming faturs. In our collaborativ Imprss applications, both th Mastr and Participating clints connct to an instanc of Imprss application via UNO; accss th functions in its API; captur and rndr th vnts throf, rspctivly. 4.2 Divrs Programming Environmnt Opn Offic offrs Divrs Programming Environmnt. It nabls popl to dvlop cods in languags such as C++, Java, Java Script, Visual Basic, VBScript, and Dlphi; on platforms such as UNIX, Linux and Windows. It has faturs of divrsity, vrsatility, and popularity. Thrfor, popl can program in thir most familiar languags and on thir most convnint platforms. This is a factor for productivity and quality of softwar, and thrfor a factor for contribution to human s common proprty. Popl can add nw functions to Opn Offic; intgrat with Java Intgratd Dvlopmnt Environmnt (IDE) through UNO componnts, and work with Offic documnts in Java Frams. For xampl, popl can program nw fil filtrs, databas drivrs, linguistic xtnsions, or vn complt groupwar applications. W can connct to a local or rmot instanc of Opn Offic from C++, Java, or COM/DCOM. Othr than as powrful as th othrs, th xtndd Java API of Opn Offic is nat, fficint and scur. As an instanc, it has vry similar mthods as COM/DCOM for conncting objcts, lik quryintrfac(), addrf(), dltrf(), Popl who ar familiar with COM/DCOM tchnology will fl comfortabl in coordinating Opn Offic objcts in dvloping and using its functionality, yt tak all th advantags of Java languag, such as its faturs for th Wb and Intrnt. 4.3 Fin-graind API Opn Offic dfins a comprhnsiv spcification dscribing its programmabl faturs. It is calld Application Programming Intrfacs (API). Ths Intrfacs ar fin-graind ach mthod (function) is for a sol and clar purpos; rlativ mthods ar groupd in a class; rlativ classs form a packag, thy call it a modul; rlativ moduls form a parnt modul, and parnt moduls can hav thir own parnt along th tr structur, until a root modul is rachd, as in com.sun.star.fram.xdsktop From Softwar Enginring point of viw, this dsign has at last th following strngths: Bcaus of its fin-graind API, it is of high lvl of rus, and thrfor it will surviv through tim. Program can just intgrat with small and ncssary parts of th intrfacs to fulfill its functionality, instad of having to includ conglomrat blocks which contain lots of unncssary functions. Thus fin-graind API maks program mor ffctiv and fficint. It maks th softwar highly xtnsibl. Extnsibility is of vital importanc in modrn softwar industry. It maks th softwar vry asy to manag and maintain. Th cost of softwar managmnt and maintnanc always is a big part in th lif cycl of softwar nginring. In both th mastr and participating clints of our collaborativ Imprss applications, th programs mak us of th functions in th API, lvrag th powr of it, and collaborat with ach othr to shar th scrn simultanously. As an xampl, w list th vnt listnr intrfacs and thir corrsponding vnt typs w trid in our programs, in tabl 1.

4 Tabl 1. Evnt listnr intrfacs and thir corrsponding vnt typs XProprtyChangListnr XSlctionChangListnr XFramActionListnr XKyListnr XMousListnr XMnuListnr XWindowListnr XContntEvntListnr XFocusListnr XFormControllrListnr XModChangListnr XChangListnr XContainrListnr XEvntListnr XTrminatListnr ProprtyChangEvnt EvntObjct FramActionEvnt KyEvnt MousEvnt MnuEvnt WindowEvnt ContntEvnt FocusEvnt EvntObjct ModChangEvnt EvntObjct ContainrEvnt EvntObjct EvntObjct 4.4 Fram-Controllr-Modl Paradigm Th Modl-Viw-Controllr (MVC) dsign pattrn [14] is popular and widly applid to intractiv softwar dvlopmnt. Basd on this pattrn, Opn Offic adopts a nw paradigm in its dvloping. It is calld Fram- Controllr-Modl (FCM) Paradigm. W discuss thm and point out th advantags of FCM paradigm in Opn Offic programming nxt. In MVC, th Modl is th application objct; th Viw is its scrn prsntation; and th Controllr is th ncapsulation of a rspons stratgy that dfins th way a usr intrfac rsponds to usr input. MVC changs th prvious monolithic programming styl in which th modl, viw and controllr ar undistinguishabl and mingld togthr to b on unit or objct; MVC dcoupls th modl, viw, controllr from th mgalithic lump to mak softwar mor flxibl and rusabl. A modl can hav multipl viws, and nw viws can b addd. Th apparancs of th viws rflct th stat of th modl. Btwn th viw and modl, thr is a Subscrib/Notify mchanism. Each viw subscribs and listns to th modl. Whnvr th valus of th modl hav changd, it notifis th viws about this. Th viws thn accss th modl and updat thir scrn apparancs. Th controllr is a rspons mchanism; it dfins th way th usr intrfac (th viw) rsponds to usr input. Th controllr objct ncapsulats th rspons stratgy which rprsnts an algorithm. Th viw associats with a controllr instanc at a tim. It can hav multipl controllrs in stor, and can add nw controllrs. A viw can chang a controllr instanc at run tim, thus chang th way it rsponds to usr input dynamically. Th controllrs associatd with th viw may hav diffrnt stratgis or variant algorithms about th rspons of usr intrfac to usr input. Th viw switchs to a diffrnt controllr objct ithr statically or dynamically, without changing its scrn apparanc. Th Fram-Controllr-Modl (FCM) paradigm in Opn Offic has som common proprtis and works similarly as MVC, but it has its own spcialtis and is mor suitabl spcially for its Univrsal Ntworking Objct (UNO) programming. In FCM, th Modl is th documnt objct; it has documnt data and also mthods that accss th data. Th mthods can chang th data dirctly without having to us a controllr objct. Th controllr is th scrn intraction with th modl; it obsrvs th changs mad to th modl, and manags th prsntation of th documnt. Th fram is th controllr-window linkag; it contains th controllr for a modl, and has knowldg about th window, but not th functionality of th window. That functionality is ncapsulatd in th undrlying windows systm whatvr platform it is. This dcoupls spcific windows implmntation from th fram, thus maks it possibl to us a singl fram implmntation for diffrnt windows in Opn Offic. Th spcific windows work with th fram to mak th scrn prsntation. Popl can dvlop nw modls for nw documnt typs in Opn Offic without having to worry about th fram and th managmnt of th undrlying windows systm. Each modl can hav multipl controllrs associatd with it. Th controllr dpnds on th modl, and controls th mannr of th prsntation of a modl. A controllr can b rplacd by anothr on without changing th modl or fram. Nw controllrs can b cratd for a modl. In programming, from a modl objct, w can us th mthod gtcurrntcontrollr() of th API to gt th controllr objct associatd with this modl; and from this controllr, w can us th mthod gtmodl() to gt th modl objct. Likwis, w can us th mthod gtfram() to gt th fram objct from th controllr objct; and w can us th mthod gtcontrollr() to gt th controllr objct from th fram objct. From th fram objct, w can vn gt th Containr Window of th fram and Componnt Window of th Componnt using th mthods gtcontainrwindow() and gtcomponntwindow(), rspctivly. Through thos window objcts, w can do jobs rlatd to th managmnt and control of th window systm. This is convnint and powrful. Th FCM paradigm is just th right thing for Univrsal Ntwork Objct (UNO) programming. 5. Th Clint/Srvr Communication Bridg Th mastr clint conncts to Opn Offic/Star Offic which srvs as a srvr, listns to vnts fird thr during a sssion, and snds th vnt mssags to a mssag brokr for broadcasting to participating clints for rndring th scrn displays as thos of th mastr

5 clint. So, th mastr and participants ar working synchronously in a sssion. Th clint (ithr th Mastr or th Participant) communicats information with th offic srvr through TCP/IP sockt. Th offic srvr listns to clint TCP/IP connctions using a connction URL as paramtr, indicating hostnam/ip addrss, port numbr, protocol, tc., as in Figur 2. Clint Offic Srvr Start Clint Procss Clint conncts to srvr using th URL connctd Launch Offic Srvr in listning mod using a connction URL Offic Srvr is listning to TCP/IP sockt on a port numbr for clint's connction, using UNO rmot protocol Both th clint and th offic srvr hav thir own componnt contxt and srvic managr. Th clint crats srvics, or UNO objcts, through th srvic managr in th clint procss, and th srvr crats UNO objcts in th srvr procss. Only th UNO objcts cratd by th srvic managrs can talk to ach othr across procss boundaris. On th Mastr applications sid, th usr controls offic fils on th Offic srvr, opning, loading, or accssing th data. In our cas, th usr controls th Imprss prsntation fils on th Imprss Offic srvr, and th mastr clint catchs th vnts fird ovr thr. On th Participant applications sid, th participating clint procsss th vnt mssags rcivd, and calls th functions of th Offic Srvr for rndring ovr thr, undr th instructions of th mssags, through automation tchnology. In ordr to do thir jobs and work with th data locatd on th Offic srvrs, both th Mastr and th Participating clints nd to stablish a communication bridg with thir rspctiv Offic Srvr and gt th srvr s srvic managr. Th procss of building such a bridg is dscribd in Figur 3. Establishing a UNO Communication Bridg btwn th clint and th Offic srvr Clint Procss : Crats a UNO Componnt Contxt in clint procss Both th clint and th Offic srvr crat UNO objcts in thir own procss. Th objcts talk to ach othr across procss boundaris to prform actions. Gts Srvic Managr from th componnt Contxt Tim Tim Figur 2. Th procss of th launch, connction and intraction btwn th Clint and Offic Srvr W launch th offic srvr in listning mod by issuing th command lin: soffic -accpt=sockt, host=localhost, port=8100; urp; StarOffic.SrvicManagr Hr, th offic srvr is running on th local host, listning to sockt on port numbr 8100 for connction, using UNO rmot protocol for communication. W mak th clint and srvr running on th sam host for convninc, though thy can run on diffrnt hosts in UNO programming nvironmnt. As in othr objct orintd languags, objcts ar usd in UNO programming to prform spcific tasks. Thy ar rfrrd to as srvics in UNO contxt. A srvic managr is a factory of srvics, which crats srvics and othr data usd by th srvics. A componnt contxt consists of th srvic managr. Crats a Url Rsolvr Srvic from th srvic managr Gts th XUnoUrlRsolvr intrfac from th UNO srvic objct Calls mthod rsolv() of th intrfac to rsolv th initial objct with th srvr Th Communication Bridg is st up Figur 3. Establishing of a Communication Bridg btwn Clint and Offic Srvr W ar dscribing th stps nxt, using xplanations and snippts of cods in our programs. First, th clint crats a local UNO componnt contxt as follows:

6 XComponntContxt xlocalcontxt = com.sun.star.comp.hlpr.bootstrap.cratiniticompon ntcontxt(null); This local componnt contxt contains a srvic managr which is ncssary to crat srvics to talk to th srvr s componnt contxt. W can gt this local srvic managr from it as follows: XMultiComponntFactory xlocalsrvicmanagr = xlocalcontxt.gtsrvicmanagr(); Th local srvic managr thn crats a srvic calld com.sun.star.bridg.unourlrsolvr, which is an objct to b usd in th connction: Objct urlrsolvr = xlocalsrvicmanagr.cratinstancwithcontxt("co m.sun.star.bridg.unourlrsolvr", xlocalcontxt ); From this objct, th intrfac of XUnoUrlRsolvr can b rtrivd, which supplis mthods to rsolv th initial objct with th srvr: XUnoUrlRsolvr xunourlrsolvr = (XUnoUrlRsolvr) UnoRuntim.quryIntrfac( XUnoUrlRsolvr.class, urlrsolvr ); Th mthod rsolv() of th intrfac is calld to rsolv th initial objct with th srvr, using th sam connction URL as that of th srvr whn it is launchd: Objct initialobjct = xunourlrsolvr.rsolv( "uno:sockt, host=localhost, port=8100; urp; StarOffic.SrvicManagr" ); Now w hav st up a bridg btwn th clint and th srvr. Th clint maks us of this initial objct associatd with th srvr to accss th data and control th functions of th srvr as if thy wr its own. It nds to us th dfault contxt of th srvr and obtains it by gtting th XProprtySt intrfac and thn th rquird proprty with it: XProprtySt xproprtyst = (XProprtySt)UnoRuntim.quryIntrfac(XProprtS t.class, initialobjct); Objct contxt = xproprtyst.gtproprtyvalu("dfaultcontxt"); Thn it gts th srvr s componnt contxt: XComponntContxt xrmotcontxt = (XComponntContxt)UnoRuntim.quryIntrfac(X ComponntContxt.class, contxt); Finally, it gts th srvr s srvic managr: XMultiComponntFactory xrmotsrvicmanagr = xrmotcontxt.gtsrvicmanagr(); Now, th clint has a rfrnc to th srvr s srvic managr. Thraftr, th clint can us th rfrnc to gt th srvr s Dsktop (com.sun.star.fram.dsktop) objct and its intrfac, which is usd to load, accss documnts (such as prsntation fils), and gt th currnt on. Objct dsktop = xrmotsrvicmanagr.cratinstancwithcontxt( "com.sun.star.fram.dsktop", xrmotcontxt); XDsktop xdsktop = (XDsktop)UnoRuntim.quryIntrfac(XDsktop.clas s, dsktop); With th XDsktop intrfac, th clint can call its mthods such as gtcurrntfram(), to gt th srvr nvironmnt s Fram, Controllr and Modl (FCM), ithr dirctly or indirctly. With th FCM paradigm, as w discussd prviously, th clint can tak control of th procss of th srvr. This is dscribd in Figur 4. Clint Procss : Gts th XProprtySt intrfac from th initial objct of th UNO communication bridg Gts th Offic srvr's Dfault Contxt using th intrfac Gts th Offic srvr's Componnt Contxt Gts th Offic srvr's Srvic Managr rfrnc Gts th Offic srvr's Dsktop objct and its intrfac from th rfrnc to load and accss offic documnts Gts th Offic srvr's Fram, Controllr and Modl to do tasks on th offic documnts across th clint and srvr procss boundaris Figur 4. Accssing of th Offic Srvr s functionality by th clint through th stablishd UNO Communication Bridg 6. Th Mastr Clint

7 Aftr th procdurs dscribd in th prvious sction, th Mastr clint has st up th rmot bridg and takn control of th programming faturs via FCM paradigm. Th mastr clint gts th currnt fram, which in Imprss corrsponds to th currnt opnd prsntation fil. It kps tsting for th currnt. If a chang is dtctd, that mans ithr a nw prsntation fil is opnd, or anothr opnd on is switchd to. Th mastr clint thn gts th URL of this currnt prsntation fil through a mthod calld gturl() in th intrfac of th Modl. Th mastr clint also rgistrs listnrs at th rmot bridg to listn to vnts fird at th Offic srvr, as in Figur 5. On of th rgistrd listnrs is th Proprty Chang Listnr, which listns to proprty chang vnts of an objct. Th clint maks th listnr listn to changs of Currnt Pag of th currnt prsntation fil objct. ProprtyChangListnr proprtychanglistnr = nw ProprtyChangListnr(); xproprtyst.addproprtychanglistnr("currntpag ", proprtychanglistnr); Narada Mssag Brokr vnt mssags Mastr Clint vnt mssags <vnt sssionid = asssionnumbr topic = atitil to = rcivr from = sndr > a slid numbr </vnt> So that ach group of popl in a sssion can snd and rciv mssags corrctly in a concurrnt sssions support and public mssag brokr nvironmnt such as NaradaBrokring Mssag Srvic. Th mastr clint dals with th URL of th currnt prsntation fil in th sam way, as in <prsntation sssionid = asssionnumbr topic = atitil to = rcivr from = sndr > a URL of a prsntation fil </prsntation> As soon as such an XML mssag is gnratd, th mastr clint snds it to th Narada Mssag Brokr for broadcasting to all subscribd participating clints for rndring concurrntly. 7. Th Participating Clints Whn th Narada mssag brokr rcivs vnt mssags from th Mastr clint, it notifis th participating clints and broadcasts th mssags to thm, as in Figur 6. Evnt Handlr 1 Evnt Handlr 2 Evnt Handlr N Controls for th srvr Listnr 1 Listnr 2 : Listnr N R m o t B r i d g vnts controls Offic Srvr documnts Usr controls th procss of prsntation fils and slids Figur 5. Th function structur in th sid of th Mastr clint applications Narada Mssag Brokr vnt mssags Participating Clint Procsss/parss vnt mssags Controls th srvr's rndring of displays undr th instructions of th mssags, by calling th functions of th srvr via Rmot Bridg. This procss is Automation R m o t B r i d g vnt mssags Offic Srvr Rndring automation documnts Whnvr a prsntation slid changs in th Imprss srvr, th listnr catchs th vnt and notifis th vnt handlr to do furthr procssing. Th vnt handlr first gts th slid numbr using mthod gtproprtyvalu( Numbr ) of XProprtySt intrfac. Thn, it dals with th currnt slid numbr by adding appropriat XML (Xtnsibl Markup Languag) [15] tags and its proprtis to addrss sssion information such as sssion idntifir, topic titl, sourc, dstination and th lik, as in Figur 6. Th function structur in th sid of th Participating clint applications Each participating clint conncts to, controls, and maks us of Offic srvr. An instanc of th Offic application is installd on th host of th participating clint, and th prsntation fils hav bn downloadd or dployd bforhand to th sam dirctoris as thos on th host of th Mastr clint. Each clint procsss th

8 rcivd vnt mssags and rndrs th display simultanously with th Mastr clint. To connct to th Offic srvr, th participating clint gos through th sam procdurs dscribd prviously, as th Mastr clint dos, to crat a rmot bridg, gt th srvr s componnt contxt and srvic managr. It thn gts control of th srvr s Fram, Controllr and Modl, and maks us of th FCM paradigm to us th srvr s functionality to control th rndring procss. Whn th clint rcivs a mssag from th Narada mssag brokr, it parss it and gts th diffrnt parts of information such as vnt typ and its proprtis, or a URL of a prsntation fil. It thn calls th functions of th srvr, such as loadcomponntfromurl(), to opn/switch to a prsntation; it calls th mthod gtdrawpags() of th XDrawPagsSupplir intrfac, th mthod gtbyindx(indx) of th XDrawPags intrfac, and th mthod slct( xdrawpag ) of th XSlctionSupplir intrfac, to navigat to a spcific slid of an opnd prsntation, tc. Th vnt typ is th ky to call diffrnt procssing functions, and its associatd proprtis ar usd in th functions to gnrat th corrct prsntation rsults. This rndring procss is automation; th functions of th Offic srvr ar calld undr th instructions of th vnt mssags. Thus, th participating clints rndr th prsntations bing prsntd indpndntly and simultanously with th mastr clint. 8. Futur Work W plan to improv our collaborativ application systm in th futur by doing th following: Intgrating th collaborativ Imprss applications with an Audio/Vido systm, such as Anabas Collaboration Environmnt [16]. This is to bring multimdia into virtual classrooms and onlin confrncing. Making th collaborativ systm work with a sssion srvr, so that prsntation/confrnc sssions can b rgistrd with th sssion srvr, and subscribd by subscribrs. 9. Conclusion In this papr w hav laboratd on th dsign, mchanisms, tchnologis and paradigms usd in th Collaborativ Imprss applications, and th Narada mssag brokr as th undrlying communication systm. W introduc th whol packag as nw distanc ducation, -Larning and onlin confrncing tools. Lik anything ls, it has limitations and advantags. Th limitations ar: th Opn Offic/Star Offic suit has to b installd on th hosts of both th mastr and th participating clint, this may b difficult for hand-hld dvics, lik PDAs (Prsonal Digital Assistants) [17]; th prsntation fils of th lcturs hav to b dployd or downloadd bforhand on th hosts of both of th clints. Howvr, with th advantags of th small txt basd mssag transfrring, th robustnss of Narada mssag brokr, and th fr downloadabl fatur and high availability of Opn Offic as its basis, th packag of th Imprss collaborativ systm will b suitabl in situations lik onlin confrncing, distanc ducation, -Larning and mor. W bliv it will contribut to thos aras. Rfrncs [1] OpnOffic.org [2] G.C. Fox and S. Pallickara, Th Narada vnt brokring systm: Ovrviw and xtnsions, procdings of 2002 Intrnational Confrnc on Paralll and Distributd Procssing Tchniqus and Applications (PDPTA 02), Las Vgas, USA, 2002, kring/paprs/naradabrokringbrokringsystm.pdf [3] Sun Microsystms Java Mssag Srvic. [4] Goffry Fox, Shridp Pallickara, and Xi Rao, A Scalabl Evnt Infrastructur for Pr to Pr Grids, procdings of 2002 Java Grand/ISCOPE Confrnc, Sattl, Novmbr 2002, ACM Prss, ISBN , pags blevntarchforp2p.doc [5] WbEx Collaboration Environmnt. [6] Placwar Collaboration Environmnt. [7] Virtual Ntwork Computing [8] Goffry Fox, Th Rul of th Milliscond, for CISE Magazin, March/April no4.pdf [9] G.C. Fox, H. Bulut, K. Kim, S. Ko, S. L, S. Oh, S. Pallickara, X. Qiu, A. Uyar, M. Wang, W. Wu, Collaborativ wb srvics and pr-to-pr Grids, Procdings of 2003 Collaborativ Tchnologis Symposium (CTS 03), Orlando, USA, mc03kynot.pdf [10] Fran Brman, Goffry Fox and Tony Hy, Grid computing: making th global infrastructur a rality (Chichstr, England: John Wily & Sons Ltd, 2003). S [11] Sun Microsystms JXTA Pr to Pr tchnology. [12] Goffry Fox, Sangmi L, Sunghoon Ko, Kangsok Kim, and Sangyoon Oh, CAROUSEL Wb Srvic: Univrsal Accssibl Wb Srvic Architctur for Collaborativ Application, Novmbr 2002,

9 sl_prcom03.doc [13] G. Eddon and H. Eddon, Insid distributd COM (On Microsoft Way, Rdmond, Washington: Microsoft Prss, 1998). [14] E. Gamma, R. Hlm, R. Johnson and J. Vlissids, Dsign pattrns: lmnts of rusabl objct-orintd softwar (201 W. 103 rd Strt, Indianapolis, IN 46290: Parson Education Corporat Sals Division, 2002). [15] Extnsibl Markup Languag (XML) [16] Anabas Collaboration Environmnt. [17] S. L, G.C. Fox, S. Ko, M. Wang, X. Qiu, Ubiquitous accss for collaborativ information systm using SVG, Procdings of SVG opn confrnc, Zurich, Switzrland, agrs/draft.pdf