Chapter 10: XML

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0 :00 امین 

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با( Giruture oP XOL Data XOL Orancedt Gchewa Queer ood ProePorwaiod Oppicaica Progra ‘loterPaces to XOL Girne ‏ام‎ XOL Duta هم با Ocsdner Cyetrw Onewpte - O* Brtirg, Px GO, OOO. wo 

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trod BXOL: Cxereble ‏ما مطهه‎ OeP iced by the OOD ‏مین‎ )060( © Qerved Prow GBOL (Strand Geoeruized Dorbup Looguee), but siopler to use tro GBOL § Oornveds have toys yivioy exica fPorwoiica ubvul sevivcs oF he domucrct © Gy. <te> XOL </itle> <slde> eirrducton ...</shce> © Gxewbe, whe TOL © Osers coo add ew tags, ood separa} speoPy how the tog should be hooded Por depray Ocsdner Cyetrw Onewpte - O* Brtirg, Px GO, OOO. wo ©Sbervehnts, Cork ced Cnakershe 

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+ XOD “kirodhwton (Ov) 11 Dhe chy spec) cow ep, od ip cred cested for structures ache XL a rect ‏مومت و رون‎ uta, oot et ‏سح‎ ‎© Dek oP the we oP XOL hoy bee to dota exckocge apphraives, ot oy ‏مساو ه‎ POL Bl Dex woke chit (rekivel)) sel demure ٠ ‏به‎ ‏وت‎ ‎> ‏حصامه_مموی>‎ 6400 >|مموس_ديمابجت‎ ۱ <boknee> SOO <inkwe> ‏حممجوول>‎ ‎> ‎0 ‎> ‏ملگ تسار ری مهم‎ sane? > ‏مسجل‎ ‏حلمیا>‎ Ocsdner Cyetrw Onewpte - O* Brtirg, Px GO, OOO. we ©Sbervehnts, Cork ced Cnakershe 

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+ XO: Oowatoa Bata hterchouge t onticd ta tokay's ‏الوب لجو لوقه‎ ۶ ‏تسس‎ ‎۱ ‏لمخاصص عمط لوق‎ ۱ 0 ‏(صطس مس رطجس) مس‎ > Gout ‏مد‎ ‎~ Chet: Okew(DL, ... ‏تست‎ OCOL (Oe-Ceqewe Dorhup Lunpane), -.- © Caper Pow oF toPorwatica betveed oryouizaices i beta rephaced by ‏مه اه روا وا‎ مت رو ۳ ع موه اه وه نی عا ‎opptcaivs ored hur‏ و( © تست صل مج ری ‎bee bevowe the busts Por dl‏ را( ۲ Ocsdner Cyetrw Onewpte - O* Brtirg, Px GO, OOO. wo ©Sbervehnts, Cork ced Cnakershe 

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+ X@L Dvarton (Ovct.) © Gorter yeverciva Porwats were bused va phoia tea wits toe headers ‏عل وله‎ ‏دا نام رس‎ ۶ ‏ما امه تون لوق‎ ۰ ‏وا سر اجه مه اه له ۲ لب و0‎ © Ded too coset ‏عنصا بيصا جا‎ dorancedt struckee (hes, spares, et) ۴ Bock XOL bored standard defies what oe vod elewects, Ukr © XO ‏موه با موه نا وا موه سر‎ » OPO (Oorancest Dupe Oreos) > XOL Grkewa © Phe text desoripiras of the secre XO) cis ‏لا با با ها تنم‎ we required © Wowever, this way be ‏را ام‎ 0 Buide variety oP tons is avatuble Por porstag, browsieny ced queries XL ‏مدل صصص جص‎ سا0 لح 0 لا سواه 1 وه ‎Px GO, OOO.‏ بسع *© - مرجي س9 لوق 

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+ Ovwpeeoa wk Rektirod Daa 11 4oePPitedt xp, whick ‏اج سوه روط موی او ما و‎ ۲ ‏ام مومسم و و لا ماج‎ © Octke rebaiced tuples, XOL dota ‏اه و وا صدط الیو جا‎ ine © Doerricgd Poreoat tage coo be ode © ‏ال‎ vested sites © Onde usceptoue, wot voly io dotobase sysiews, but der tt browsers, took, ‏اه و‎ Ocsdner Cyetrw Onewpte - O* Brtirg, Px GO, OOO. wr ©Sbervehnts, Cork ced Cnakershe 

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Crwtre oP XOb Ou ‎Por a sect oF dott‏ سل یی ا ‎wih Spryocre> cond eck wih wach‏ رام تاه مه سا > ‏ای سس سا ی ی ا ‎Gite‏ ‎<a> ... Sbokne> .... <S/bukne> <ai>‏ ” ‎© Aoproper vestry ‎١ <at> ... Sboknoe> .... Slasmmni> </pre> © Conny: every stort tec cust have a uakque oatchiery eerd fer, that i ict the otter oF the suxve ‏ای موم‎ ‎© Cvery donned weet hove ‏اوه امه له و‎ ‎Ocsdner Cyetrw Onewpte - O* Brtirg, Px GO, OOO. we ©Sbervehnts, Cork ced Cnakershe 

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+ Gxanple oP Osvied Cleweus <> <ورومواضج> هلک وبا <جدكمد_وصصاصى> ‎Dart </amiexver_sireet>‏ <اسه_ مس و> ‎<mestower_piy> — Wanisva </ostower_viy> ‎<at> ‎> ‏امه _ موه > 0409 امه موه‎ > ‏واگ لصو‎ > 00 ‏<عصل>‎ ‏<حججو> ‎> ‏حاوممموو> ‏حوموصو|> ‏<الجاما/> ‏مه ‎Px GO, OOO.‏ بسع *© - مرجي س9 لوق 

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+ Ovwaiva Por Oeotay Bete oF ta ie weed ta dota troy © Groople! records represrukn meiner ‏مه اس هه‎ seed eat ore roche ‏مسا‎ ‎BE Westen ‏مه‎ supported, or decourned, ‏اد اما و‎ © tk ‏لت‎ orders, custrwer anne ond ‏ولب‎ ore stored reckankrly ‎cesied structures is ack order by Poreiga key ini table‏ او من و اوه ی لوصو منود ‎© Destiog & supported it object ekticad daotobases © ®t cestioy is oppreprist uhec trasPerray dott © Cxterad uppicaiva doer ot hove direct uovess to dota rePereured by o Porter kev ‎Ocsdner Cyetrw Onewpte - O* Brtirg, Px GO, OOO. 

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+ Orwtee oP XML Oca (Ova) BO inture of text wily sub-elewets ts beyal to XOL. © Cxnvple: > ۳ ‏یه و امه‎ werd cay wore. ‏حجتاسم_سحووو|> 0-00(6) حججاسم_سحدحه>‎ ‏<حعهم_عاممصط»‎ Perryridye</brauk_enve> > ‏سوام‎ < ۳ > < مها > او ول و( وحم تا ,موی مج ‎OsePul Por‏ © Ocsdner Cyetrw Onewpte - O* Brtirg, Px GO, OOO. wa ©Sbervehnts, Cork ced Cnakershe 

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+ Otrbuss © @eweds co ‏اف چم‎ Soret wertype = “checks” > <uoomnt_avber> B-IOE </accoucit_sober> <brooch_ceve> Perr yridye </broack_sane> <botrace> POO </bckrace> > مه ما و ‎rete the starter‏ مساو را اجه اه 19 ۳ Qo dewedt way kee severd airbus, bul cack oirbue cere ‏صمت سوه رات موه‎ 2 ‏رهب‎ a ‏سیم‎ Ocsdner Cyetrw Onewpte - O* Brtirg, Px GO, OOO. 40.00 ©Sbervehnts, Cork ced Cnakershe 

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+ Orbuse ve. Oubelewous اه ای له یا مت( ۲ ماه ات ,موی اه موم و اه تحص چاه مس ددا 215 8 ای مج مان نهر و ان © ‏میم عا و‎ oP data represeutaivn, the ‏امن تا وال‎ ood way be rant rey > Gewwe kPorwaion con be represecied a hor wae - > ‏ماک <0400 ۹ ام مه‎ - ‏مس‎ ‎> ‏حوطججح_سجووه|>0100-()حوناصج_ سمدم‎ ... > ‏مس‎ ‏اه بو سوسوم ما ل‎ Por ‏وله و لو مر و مت‎ ‏ی با‎ Ocsdner Cyetrw Onewpte - O* Brtirg, Px GO, OOO. 00.00 ©Sbervehnts, Cork ced Cnakershe 

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Onwespwes ۲ XOb dota hos te be exchooyed betwees pryqusizaicns ۲ Gowe toy coe way have ‏دا مه تال‎ dPPeredl oreaizaioes, cousin ‏وتو‎ oo ‏او‎ domes © GpecPyioy voique sirtog os ‏وی ماه مه‎ voids oooh ira توص :مشاه طو) ۲ ‏یه عون با رم سر‎ ol pver doruvedt by usiegy XOL Oexvespaces: > ‏حامس‎ Kerker P@= ‏تس( یاوه‎ < اسم :00> <وبوصوصاصحمصجا: ذا):)/>مسصخحسص(])< سردو صاصدسا: ‎<P‏ <روصطاسموا: 0۵ > مواس<) > ۳0۵ ‏<رواسمو:‎ ‎</P@tbroach> <عامبال> ‎Px GO, OOO.‏ بسع *© - مرجي س9 لوق 

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QOore va XOb Gyniax ۲ @leweus wikout subeleweuis or text cvoied coc be obbrevicied by radi the stir ‏كما‎ ‎wits a /> oad deletions the eer fer </ (00ات"حعصمسما ۱ جه له رها و لا مات ,و ی بو ال پم ‎Po sire‏ © ‎subeleweds, wer ODOT us bel‏ ۰ >] ۵] ... > ‏<[[حمسسس‎ ‏عه لفيا ده ی جل‎ pet ee ere COTO stands Por “chararter kta” Ocsdner Cyetrw Onewpte - O* Brtirg, Px GO, OOO. 00.00 ©Sbervehnts, Cork ced Cnakershe 

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+ X@L Oronced Ortewa ۲ ‏موادت(‎ schewes coustrais whol iPorwaiva cod be stored, ond the dota pes OP stored values © XOb doranvedts ore wt required ty hove om wevrited svhewa 18 dhowever, schewer oe very Reported Por XOL dott exch ۶ ‏,شمان‎ 0 te cocut oui@utivdly toerpret data received Poo carter vie © Dw werkuisws Por spevP yen XOL sckewa © Oorancedt Type ‏م0‎ )0۳0( * Ordely used © XOL Gchewa 7 ‏رو یو(‎ use Ocsdner Cyetrw Onewpte - O* Brtirg, Px GO, OOO. 40.00 ©Sbervehnts, Cork ced Cnakershe 

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+ ‏سم‎ Type DePraioa (DTO) 10 11 ype of ot XL doranvedt con be spevPied usta ¢ DTO BODO cewiranis sinwture oP XOL cata © Oke tewents van pour ها مه مه ‎coolest‏ ات ‎Oke‏ © © Oko abel weds coolest poour inside cack elewed, ued how way, ‏ی‎ حجر مد مت بت ی 0۳۵ ۲ ۱ مج بت لت لس 0 ‎٩‏ مد 0۵ ۲ < (متاسسسممسلم) مس ۱0,۵06 > ۰ ‎eewed (ctrbutes) >‏ ۵۲۵۲ > ۰ Ocsdner Cyetrw Onewpte - O* Brtirg, Px GO, OOO. ‏سا0 لح 0 لا سواه 1 جوهه‎ 

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+ @bwed OperPrara a OTD Babbar ean be oped el ce ۶ ‏را اه ی‎ oF © HPOOOTO (paved charmer ‏مه مات سا ز(صقل‎ © BOOTY (cv aubekwects) or 00۲) ‏سل هسام‎ ۱ ‏ات‎ ‎> ۵۵0۵ ‏ی _ممسم) ماس‎ wxrnnt_sanvber)> <! CLEOOOT ‏مسی_سسی‎ )#6000/۵(< <1 CLODGOP exxxrsct_snvber (HPOOHDO)> B Otbebwedt speoPivatva way have reqdar ‏وی‎ ‎<IPLEOCO ‏ححص ) ) جلما‎ | rwteswer | depovitor)+)> < Doren مس و و "و ال مج بت و 00 ۲ Ocsdner Cyetrw Onewpte - O* Brtirg, Px GO, OOO. 00.00 ©Sbervehnts, Cork ced Cnakershe 

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+ @uk OTO > ۵۵ ] <IGLEOEOT bank ( (cern | etree | depesior)+)> <IGLEOEOP cecrand (ceoeret_manber browh sexe bokre)> <! CLEOECO? asiwer(asiwer_anve mptnrer_sieet ‏ی‎ >! CELEOEOD cepostor (aetwer_senve eant_onober)> >! GELEDEOT cerrrrt_savber (HPOOBNO)> <! ELEDEOT breech _cexve (HPOORTO)> >! ELEOEOP ‏)سس‎ 000091: )3(< >| ۲۵0۵ ‏<(#۵06/۵)سی_ سس‎ >| ۲۵0۵0۲۳ ‏سموه_ سس‎ #۳000۵ >! ۲060 ‏<(00/۵)#)بو_مسسه‎ Pp Ocsdner Cyetrw Onewpte - O* Brtirg, Px GO, OOO. 00.00 ©Sbervehnts, Cork ced Cnakershe 

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+ ‏سا‎ OpeoPodra ia DTO ۱ trbue specPicaioa | Por ‏اميه الوم‎ © ‏سم‎ ‎© ype ‏اف خر‎ > COKTO » AD (MeciPer) or WOREE (10 rePerewe) or WRERG (catiple REPS) ‏سا ام و‎ © ‏ان‎ ‎« ‏ملس‎ )۵۵0۱60( + ‏نع‎ defind cher (uch), » or wether (#DPLIEO) B Croke © OTNACT arnt wotpe COON “checkin> © > ۵۲/۷۵ ‏مه‎ ‏ل مهد‎ 10 # ۵ ‏جمد‎ 10۵6۵۵0۵060 > Ez Ocsdner Cyetrw Onewpte - O* Brtirg, Px GO, OOO. ‏سا0 لح 0 لا سواه 1 موه‎ 

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10000۳2 مه 4002 ‎hove of west ove otros oP ype 1D.‏ موی موه و( لا ‎BD ke 10 atrtbute vole oP buck ele wed on XO) doranved cust be ‏اس‎ ‎© Drop the 10 ottbute volte is oe object ‏تا‎ ‎© Qo atribute of pe TORE wast ovata the 1 ‏موی من نصا‎ fo the ‏مج وود ‎a set of (D or wore) 1D voles.‏ یس 106 سره ات ۲ مج ‎pe‏ ۸ ۰ مرب ‎Back 10 vohue wet ovotoa the 1D vohue oF‏ ‎Ocsdner Cyetrw Onewpte - O* Brtirg, Px GO, OOO. ‏سا0 لح 0 لا سواه 1 »وه‎ ‎ 

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+ ack OTD wik Orrinies ۲ Gack OPO wk 0 ord WORE ‏که‎ turer. <DOOTYPE bxxk- Ol <IBLEOEO verre (brows, bokeee)> مه > ۵۵ # 0 اسر سس ۵601۵60۶ # 1086606 ره 1 apie _siert, <(ه سم <IBD IGT asiower meter 40 # ۵ ‏ی‎ TREES # REQOIREO> . dedoraizgs Por broock, bokrase, custocer_xeKve, ] ood mstower_viy Ocsdner Cyetrw Onewpte - O* Brtirg, Px GO, OOO. ‏سا0 لح 0 لا سواه 1 موه‎ 

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+ NOL dae wik W aad WREE ‏ات‎ >< > ‏)موه 00 امه‎ 00067< > ‏هجو‎ > ‏<عصدداصا/> 0000© <عصدامجا>‎ > <ousiomer ‏مه 00000 لسع‎ )0000< > ‏ل<عسی_‎ </owstower_sexve> <newwer_sireet> Ovave </nustvwer_sireet> <mewwer_viy> — Oxdisva</custower_vipy> ‏حوموصو|>‎ ‎> ‏میت 00067 دمصت‎ ۵400 0065 <asinver_oave> Day ‏هه‎ ‎<custower_sireet> Bric S/awtower_stireet> <pewwer_viy> — Oewurk </oustower_viy> ‏حوموصو|>‎ ‏<لمی>‎ Ocsdner Cyetrw Onewpte - O* Brtirg, Px GO, OOO. ‏سا0 لح 0 لا سواه 1 موه‎ 

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+ Licotaowes oP OT Os Be typi oF ‏اه له ماه فا‎ © Oluckes oe six, ‏ات رن ها من‎ ۲ 0 to ‏مه‎ vaordered sets oP ‏واه‎ © Order ip nly irrelevant te dotubuses (vole to the domreecthyrut eoiroved Prow which XL evolved) © @ | ©) dws speoP dion of ‏فا رت ای مه‎ > Camert pare that park oP @ aad @ poms oly roe BW ocd TRE Ps oe vce © Dke nwuers otinbute oP oc acorunt way oodtain a rePereore te cote ‏موی ها ات ,اوه‎ وه وا ان وا یی سا رال له ماه حوو ‏ ماه Ocsdner Cyetrw Onewpte - O* Brtirg, Px GO, OOO. woe ©Sbervehnts, Cork ced Cnakershe 

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+ X@L Orkewa © XOb Gchewa is 9 wore suphisicded sche hrauage whick addresses the drawbacks of OTODs. Supports © Dy preg oF yokes * @.x, rteyer, siren, ‏اه‎ ‎۲ ‏موه ,بط‎ va wiolwax voles © OserdeRaed, cowlex yer © Ooo wore Peutures, fochudkay ١ ‏فصيو" لجن دعص وص‎ hey pocstrains, tcheriaare © XOb Gchew is tse spectied in XOL syotax, uthe DTOs © Oore-stondard represeutaiva, bul verbose © XOb Gchewe tf iteyroted wih ‏ی‎ ‎B GOT: XOL Gchewa ts siqaPicodly wore cowphcdted tat DT Os. Ocsdner Cyetrw Onewpte - O* Brtirg, Px GO, OOO. ‏سا0 لح 0 لا سواه 1 موه‎ 

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+ X@L Ockewa Ovrsiva oP Bad OTO سا ,۵ ۱)۱۵۱/۷ کرو نکر سا هکم امد مورک <ol> ‏سیک‎ exon ="aoorant_sanvber” ype" birt /> ‎we‏ مایت كد لماعك <عمصجسووهم|> حسبرالصام عمج :| > > .... اور لو ی اه مه <'سور )وه سر سامممونم> سوک 7 0 < ی سوه )وت ۳ موه روط موی > < یک هکم ۳( موه( توس > > ‎Dype>‏ سابوممسنمل> ‎</xetovkewa>‏ ‎ ‎ ‎Ocsdner Cyetrw Onewpte - O* Brtirg, Px GO, OOO. wee ©Sbervehnts, Cork ced Cnakershe 

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+ X@L Ockewa Ovrsiva oP Bad OTO © Choice oP xe.” wae pure — ony her oneespare prefix could be chose © Clewen “buck” hos ype “Back Dye", which ip deProed seporciely © xstorwplex Type is ved biter to oreute the canned complex Ve “Bad ype” © Glewed “arco” hus its type dePiced terior Ocsdner Cyetrw Onewpte - O* Brtirg, Px GO, OOO. wor ©Sbervehnts, Cork ced Cnakershe 

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Qore Peaues oP XOb Ockewa © Otrbutes ‏اند روا تاو‎ ter: * >: ‏<الجتامصجح_محصحه" - ممم صحاف‎ © هلكلمي ‏لجتامجمد ججا اصسجه عداس عمصم "لجمشوصم" 2 وب صنجاطه هذا‎ © ‏و ای مت تم رو‎ a hey Por ‏یی وه موه‎ the ‏تاه لا اسر‎ > ‏روا مج < موم بو‎ > ‏سح لطس < مود موی‎ < ‏و سک و‎ ‏<روانی>‎ ‎۲ ‏تمه وا ود ما موی روا و‎ > ‏نج )الصممي وا توا همطل < سم سای‎ < Sxeiselevior xpak < ‏سح لطس‎ < > ‏لاس سس < گم الا‎ < ‏و‎ Ocsdner Cyetrw Onewpte - O* Brtirg, Px GO, OOO. ‏سا0 لح 0 لا سواه 1 موه‎ 

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+ ‏لت برس‎ TrawPorckey XOL Oda ره و موه با نموت متا ‎des‏ امس ‎took‏ وه ‎by‏ لس ای لصا ‎Obove tie ore closely‏ ما هلوس با للم ۳ 9 تعسو اجه مه مممها وق ‎xo‏ © تا لو با و تلا مت متا ‎Greople hoocquage destqoed Por‏ * ‎to WOOL‏ © ‏ص6۵‎ ‎١ Ba XOb query kregquerge wil: a rick set oP Pectures: Ocsdner Cyetrw Onewpte - O* Brtirg, Px GO, OOO. ‏سا0 لح 0 لا سواه 1 وه‎ 

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+ Tree Dede oP XOL Oca © Qhery od texePorwaivs kreenges ore based vo ‏و‎ tree wodel oP XOL data Ba XO) donned & worded os 0 tree, wih wdes correspradiny ty elewents ond ‏اه‎ جوم واه مه ماع موی انیت لاه سره له ام ماك دما خام ‎Dex tooo peur ts wordeled aso text orde chid‏ ‎te their order to the XOL dorancect‏ عمل صصص ‎Obidres of a onde are ordered‏ Clewent oad ctirbute codes (except Por the root code) hove o pind parent, which oc pleut oe (© Phe root ade hos a siege chi, which is the root elewedt oP the domnvect Ocsdner Cyetrw Onewpte - O* Brtirg, Px GO, OOO. woo ©Sbervehnts, Cork ced Cnakershe 

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+ X@uk Bl XPak & wed tp ckbese (orton!) parte of ‏ص دمجم‎ poh previ ۲ 0 poh expressiva is u sequewe of steps ‏امه‎ ‎© Dhick oP Pile caves foo dreviory hierarchy BO Result oP pak expressive: set of values thot dca ‏ی کیت‎ ‏جلدم لاه سا اس اه حول‎ ۱ ‏اس تلو مومسم ع‎ bool) cuter we sew porter retires Scustower_sawe oe </rstcer_xnnve> Smusiower_sae>Oory</asiower_snrve> Gk, He eae th ee returnees the ‏مش تج ,موی و‎ the coclosicny ‏كعم‎ Ocsdner Cyetrw Onewpte - O* Brtirg, Px GO, OOO. ‏سا0 لح 0 لا سواه 1 موه‎ 

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X@uk (Cou) BD he ‏لصم‎ "1" decries root of the dorancect (cove the to-tovel te) Bl Pak express oe evchnted fA to right © Gack sep operdes on the set of etree produced by the previne sey 11 Getevies predodies way Polow oy step tra pot, [] * ‏ساس مس اما بت‎ < POO] reine ‏مما محفصي صان سل و جلانن اجات ححص‎ POO ١ ‏یاه موه اه لمحم مسجم [عدمامط] مت حصط اما‎ ‏ملد‎ 1 ‏ماص‎ "©" © Cy, ‏امه_مم 6 [600۵ < مساق‎ ۱ ‏یی‎ he orcad axnobers of arconte wih bokare > POO ۰ 10۵6 ‏مه سس رهاط بت بو لته‎ his ter) Ocsdner Cyetrw Onewpte - O* Brtirg, Px GO, OOO. woe ©Sbervehnts, Cork ced Cnakershe 

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+ Cxrstrw to XP ok ۲ X@ak provides ‏عمط اوه‎ ما مات خن ای سا عقوت تم و ‎othe eed of‏ ( مت مش © ‎pats‏ بط را لهس بو با ۱ ‏(سسها امس اما مق‎ < ©[ - ‏مه مق‎ wth > 6 ‏هه‎ ‎۶ ‏مس سا‎ Por texters ponies ((, ©, ..) oP oe wart. ‏ماه‎ ‎Bl @ooeon ‏صخا لم اذ لمي اج صم صمي‎ oo) cam be weed ia predicies ۶ WRECPs cos be rePerewed iste ‏میت‎ 0)( © id() coo dsy be opted to sets oP rePereues suck os IDRECG ond ever ty ‏امه و( وال بای وه‎ by backs لجسم )سمه ا حصا .© © اجه ‎oP‏ اه نی | مت نا لاصو اه سب هی Ocsdner Cyetrw Onewpte - O* Brtirg, Px GO, OOO. woo ©Sbervehnts, Cork ced Cnakershe 

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+ Ove XP ck ‏وس خسن‎ Bo Operdor "|" weed to Roped ira © Bx, Ibo Clhemmnild(@oweer) | ‏سا‎ @berewer) ١ Bies nrtrers wih ether acco nts or borer > Whowever, “|" can be ‏له‎ ide ober operdore. BY? oxi be veed to ship crue levels oP codes © ‏ومم_ ححص و|اقطما مه‎ ۱ ‏جما عصلمب جمجطانييوه مجك بمد_وصماصج نوه‎ [bora ‏ای ۱ جات و ماه سا اه ميب امسر‎ © 0 step tothe pub coo yw ty poreus, siiogs, co | ch dercits oF th ‏تحص لیم‎ by the previous step, uot et to ‏یاهع‎ ۰ ۰ desorbed chove, ‏جا‎ 3 shor Brow Por speck ian ‏"عم مس‎ © 0 species be pared. Boo (cane) retarces the root of 9 oenned doranvet Ocsdner Cyetrw Onewpte - O* Brtirg, Px GO, OOO. woe ©Sbervehnts, Cork ced Cnakershe 

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XQuery © XQuey tp 0 geverd purpose ‏عمجت زر‎ Por XL dota ۲ ‏روا تلو ما رامین‎ the Dortd Dice Deb Oowsoritn (DOC) © Dhe textbook desorption ts bored vo a kenny CDOS droht oF the stantard. The Pied versica way dPPer, but oor Peutures likely to stay ‏ی‎ ‎© XQeery is derived Prow the Quit query lrogquage, whick ‏سس ام‎ Pro GQL, XQ ved XML-GL ۲ XQen wes ‏ه‎ ‎Por... tet... where... order by ‏لفجحب...‎ یرو ‎GAL Pow‏ جم ‎where © (GAL where‏ ‎order by © GAL order by‏ سید ‎rent © GQ‏ ‎equidect kr GAL‏ مه ‎bt dws teeporay vorkbes, ond kar‏ Ocsdner Cyetrw Onewpte - O* Brtirg, Px GO, OOO. 

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+ 6006 6+ ta XQuery ۲ Por knee wes X(Puk expressions, ond vorteble ta Por ‏واه‎ renee over voor i the set retired by Xa ۲ Grope PLOOR expression it XQuery © Pred ol arom eis wits bokere > POO, wik euk result eocboeed te ort ‏هما <جطامسی_ میلگ .. امس _مجمی>‎ Por See kl ee ‏با‎ Sunt ‏ام ما ع:‎ ‏ما5 ات‎ < 600 ‏حجباصج_ سح !> ( سل ) < ایتک مور‎ © ‏وات فصا با( )ا صمت وجاك مممجور ححا دا سسا‎ eorksed tc {}, ter hick rose they ‏عامج و‎ © bet cknse wt redly weeded to this query, ood selective coo be doo Io XPak. Query pan be writes a! [0000:)<سسممامجا] صصص | 6 حامص ا ‎Por $x in‏ حك م5 | اس رس سب _السجوهه|> ‎Px GO, OOO. wee ©Sbervehnts, Cork ced Cnakershe‏ بسع *© - مرجي س9 لوق 

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سل + Boke oe sperPed iro omer very stoke 7 GAL Por $0 ta lint, $0 te ‏ماس طاطحنا‎ 50 ۰ ‏سل‎ ‏الط < چام پیمولد؟ وان‎ ‏موجه واه؟ له‎ ‏حمسو سه معنن‎ | Se Say ee Bh Dhe sowe query oon be expressed wik ‏مراد‎ spoofed we XPak سس رل سیب وت <اسه_صهاک> ( 50 92 ) حاممد_صج> مور Ocsdner Cyetrw Onewpte - O* Brtirg, Px GO, OOO. wor ©Sbervehnts, Cork ced Cnakershe 

صفحه 38:
هس + 18 ‏وه توص پا با‎ dota Brow the Plat structure Por boots ‏ما وت‎ the vested structure used tt boc! >< ) Por $e ta foo stower rer <pustxrer> { $o/"* } ‏الم سما لم + ی‎ a ‏سب‎ $a} > ‏مسا‎ ‎( ‏<مال>‎ ‎© Sol* dewtes oll the chidres oP the ode ty whick $r te bowed, wihout the eodlestery top fevel tory BE Scleni() ‏ماه روت جات ماه مخ مت بت رف‎ | kre Ocsdner Cyetrw Onewpte - O* Brtirg, Px GO, OOO. wee ©Sbervehnts, Cork ced Cnakershe 

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+ Gorkay ht XGhaey 15 Dhe ordbr by okay vont be wed ut he ead oP oxy expresvion. Oa. rekra nwiwcery sorted by ‏مرس ولج ۰ 5 بیط‎ [7 envy ‏حجومسو|> ( *إ30 ) ججمصافى> مسج‎ Bl Dor oreky by Suletruer_snnie tp ort ١ ‏عطست مط مسصصسة‎ ‎onal by accent_xurber wikia rack‏ ,وی ی ‎(oot by‏ جناي ‎Qo oor ot andy eves oP‏ ها ‎ ‏مامت ‎<tr> {‏ و ۳ ‎rhe‏ ‏ی ‎$ol* }‏ { ی ما یکی مومس ج ول ما ۰ 5۱ ‎Por‏ { [ [جایی_ سکع جوامیه_ نسم ]لها موق جیاتن5 ‎by‏ ی ‎retars Sarat $al* <laromnt>‏ ‎Shawnie‏ ‎<br>‏ } ‎Ocsdner Cyetrw Onewpte - O* Brtirg, Px GO, OOO. wee ©Sbervehnts, Cork ced Cnakershe 

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+ Pawan Gai Our XGhaey Cackrer ‘he * (ve ta decked) indicus 0 sequeue of uch of thot ire ۳ 0105 ‏بت سیخ لت‎ the type systew of XOL Ocho Banton bokraes (xe ‘striee $12) retary boi(neidevicrd") { Por $d ta (buch! depostor[amiower_senve = Sr], ‏[ا_ سل < لیاسم ولا دا و3‎ سمل متا } 19 Dyes oe opiived Por Puontica poraweters ocd retura volves © Ocversd ocd existential quaciPicdiog it where ck ‏وحم‎ © sowe $e ta pak sobPes P © poy $e ta poh sues P © XQuery dbo supports hewebe chases مومه ‎Px GO, OOO.‏ بسع *© - مرجي س9 لوق 

صفحه 41:
XOLT BO vptevhert sires Porwutioy optivos Por a domed, usudly separdiely Pow © Cy. vo WT OD sie sheet way speck y Poot oolore aed sizes Por heuckorer, 3-3 ری و لحم نمی سم (را))) بحس حصنا اسسدإسارو) 001لا 11 19 مس باب ۲ ‏موم ماو ملس وت را‎ © ‏بل تلا لت تلا سا رل)۷ا اسب ون‎ ۲ ‏ه شوه را‎ expressed wet nes coed tewphies © Dewphtes cowbice selevtiog ustoy X Pubs wit: coustruntion of res ue Ocsdner Cyetrw Onewpte - O* Brtirg, Px GO, OOO. ‏سا0 لح 0 لا سواه 1 موه‎ 

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XGLT Tewpkiss Crcrople oF XLT texopkte wits xvi ond elect port > ‏سا کم اس بسا‎ < ‏ی‎ ‏اراک‎ ‎> ‏ساسا‎ cote" > ‏ا‎ atk ‏و مس و موه اراد ان سای‎ ۲ ‏تا‎ ta the ‏ست من ما مایت تحص با‎ processed by the ‏وميه‎ wikia the xobiewphite ‏سماد‎ ‎© ‏مزا‎ selents (ours) specPied ucker (here, oveiwer_snre) ۳ ‏ات روم ای بت ول ما مسا و‎ © ‏یله‎ cen text oocteuis are ult © ‏له مه لاو راومه ار‎ ‏ا‎ ‏و مجان وج شومر ارود تك وجل موصو سم‎ © Oped ‏که بات بل مرن تا مسجت و‎ رو موه و من لصو لح جا وه رام مها اوه اون ماه مه ۱ ۲ اس سوه سود Ocsdner Cyetrw Onewpte - O* Brtirg, Px GO, OOO. wee ©Sbervehnts, Cork ced Cnakershe 

صفحه 43:
+ Orectoq XOL Oup Buy tent or iy ithe XBL sifechert thot i ol fa the 20k waweepare by ouipul or i Bg. to wep ren in ‏,اه را( تنم‎ <xshtewphate wratch="/bods-Olrustrwer"> > ‏مه ای امسامناو>‎ > ‏۲ص‎ < ‏سا‎ ‏اس سامم‌سنای>‎ < © Gxexople vulput Sawtower> doe </oustower> <aetirwer> Day </oustower> Ocsdner Cyetrw Onewpte - O* Brtirg, Px GO, OOO. wee ©Sbervehnts, Cork ced Cnakershe 

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+ ‏مهن‎ XOL Ouput (Oo) ۲ ‏و‎ Coca dreniy tosert 0 xelivdue-of tog tostde corther tory © G5, cama cred ‏ویک بط مه‎ ta he previne emnope by ‏اس‎ ‏سس نام وی‎ مه سا جوا نا سا هناهد صصمت و لوا ۶ پبپ۰ب-دددسسا- حمسه> وه ۱ مهس ات اس> <ا_مست" > اسایه سل نامک <س وا ها > <ممسول> 9 “م ۱ اه صمسعصی> ل ل و ل ا 22س ‎Px GO, OOO. wee ©Sbervehnts, Cork ced Cnakershe‏ بسع *© - مرجي س9 لوق 

صفحه 45:
Grrwtard Reowswa ماه ‎Decopkte ontea cos opp) terres recursively 7 ke poaiccts oP a cocked‏ للا ‎<rohtewphite wich="Iboh”>‏ <asiovers> Srobtewphite ppl terphies!> ‏صومحصو|>‎ < <roktewphie> <roltecnphae vack="/ostower"> <custower> <rohvohe-vP ‏سس تساه‎ ‏حوووصج|>‎ <roktewophte> < ۲ص صطاممجنای> B Crop <nstowers> <pstower> loka </rustower> ‏حوووصج|> بجو() حومووصج>‎ حمورووصو|> ‎Px GO, OOO.‏ بسع *© - مرجي س9 لوق 

صفحه 46:
Notes ta MOLT ۲ ‏را‎ keys dlaw clewests ty be looked up (indexed) by ‏تاش مه وله و تلا‎ ۶ Qeye onet be decked (wil a unre) ond, the hep() Puortion coo thea be used Por ‏مسا‎ 2. کی وکسم روااو> <ا مکی (۲۵ :مس واه امسد راک را ۱ ‎Beye perwt (sowe) pre ty be expressed‏ <الجاصج_ مح "حبس " "تاعفار "ماسح حصب بود نايك موی هه ای تکوم راو > < سس ای صاومس ای > <سه_سی> <ا( سس ,ماسجا )سوه سل ناک <ا( یهن ,)ره اس زا > حسم_سو> <ص اهنا > امس سمامسسنامی> 4 Ocsdner Cyetrw Onewpte - O* Brtirg, Px GO, OOO. wee ©Sbervehnts, Cork ced Cnakershe 

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را سم + Osta ‏ام‎ drevive teste o tewphite cases ofl eleweuts waichiey the tecrptae to be sorted ارس مان ری ساسا مس ‎Garten‏ © Sxshiewplate watch="/back"> <xshupphtewphies selevt="rsinwer”> > ‏سس موه موزل‎ < Sheskapphewphies> > ‏ارجام‎ ‎>: ‏<”لوموصج "حجاعوجم جاماومج‎ > ‏<اعمم_صصمصصج "حامجايد “اص اسذات>‎ ‏<|”وود_صوصصاصج "حامجايه “اص اسزات>‎ > ‏روص ی سای مصامنای‎ < ‏حوووصو|>‎ ‎> ‎> ‏ون ماو‎ "| < Ocsdner Cyetrw Onewpte - O* Brtirg, Px GO, OOO. wer ©Sbervehnts, Cork ced Cnakershe 

صفحه 48:
+ ‏سس رت‎ (Progen ‘hae Par Bl Dhere a to stented ‏اد موس مار‎ to XL cheat © COX (Giore BOA Por XOL) » @used va parser wodel, weer provides evedt hoaders ‏ره رم و‎ ‏ور‎ stat oP cewed, ead of rece ‏وب دسج و(‎ © DOO (orrncect Obert Ort) > XOD chia & parsed kyo tree represectaios > Oar oF ‏للم مس‎ Por ‏رورم‎ he DOO tree « ‏توق‎ dart OOO BP provides Dede chase wth weeds [۱ ), ‏)صاطق دناس ,( )لل ساس‎ ( xe(Birinte( ), ce(Dcta( ) (Por text coe) ‏هت ات‎ ), 2. ١ bp provides Pucetioas Por updater DOO tree Ocsdner Cyetrw Onewpte - O* Brtirg, Px GO, OOO. wee ©Sbervehnts, Cork ced Cnakershe 

صفحه 49:
+ Ovrag oP XOL Owe © XOb dota co be stored it © ‏وه بل مایمن‎ ٠١ Phot Pies ~ Oxturdl Por stortery OL — ut kos oll problews deterred ta Chapter 0 (a7 earurrruy, ‏جم‎ ‎recovery, ...) * XOD database ~ Oxtobuse bult specPicdly Por stortag XOL data, supports DOD ‏ی سول له ال‎ - ‏رو وولو و زان‎ © ‏مش‎ dotcbors * Dota cust be trocstated toto retaticod Porc * Odvactage: woture dutcbasr systews * Osadvadtages? overkead oF trocar date cod queries ha Ocsdner Cyetrw Onewpte - O* Brtirg, Px GO, OOO. wee ©Sbervehnts, Cork ced Cnakershe 

صفحه 50:
مومه ‎Px GO, OOO.‏ بسع *© - مرجي س9 لوق 

صفحه 51:
+ Grey Represeckiva اد ماه و عون تاه الم ‎BE Gtre ewok tp bevel elewect oF 0 sito‏ عن اه سوه وا مق ‎Ose connie‏ © جور مه امرطوت ات و ما موه و ‎Ope‏ © اس و وه ره وق ۱ مه ‎to store the‏ هروه و رس او ‎he‏ هط ‎to be tendexed as extra‏ ها ‎Gre uch of sibel‏ © ‎hove Pick‏ مه لها اجه متیر ام روج و هو ‎١ Bax,‏ © Gowe ‏رل عون نموه مرو تال‎ whick use the result oP ‏ی توا اجه ی(‎ ۱ Dhe Puantiog should retura the vdlue oP the required subele went ‏اه‎ Ocsdner Cyetrw Onewpte - O* Brtirg, Px GO, OOO. 00.60 ©Sbervehnts, Cork ced Cnakershe 

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+ Oriaq Reprevecktioa (Ova) © @evehic: © Com sire way XOL dota even witout DTO © Os troy os here ore wony toptevel cleweuis io domed, ‏اه‎ ore awl cowpared to Pull dorancect ١ Blows Post access to todvidud eleweuts. ۲ Oraubuck: Deed ty parse sirays ty uovess voles tside the ‏اه‎ ‎© Posie is slaw. Ocsdner Cyetrw Onewpte - O* Brtirg, Px GO, OOO. woo ©Sbervehnts, Cork ced Cnakershe 

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Vree Repression Bl Vee repreveunion: ‏بلست‎ XO) det os tree ond store usin rehtiocer sexks(tl, tare, kel, whe) chk (ctl td, rorect_rd) brschs (nk) rastrwer (iO) ‏نك) سح‎ 6( ‏امه 0 سم _ مجان‎ ۵ 9( (i: ( ام وی ه فا اه موه او ۲ ‏اه امه عصلی‎ ter Lobel speviPies ‏اه وله اه و ركم جما‎ trate Ondue tp the text udue of ‏امه سل‎ ke relics chit wtes the parcat-chid rekiicaships tc the tree اجه اه ره لس وا لالم ‎Cecodd oo exira uiribuie to‏ © Ocsdner Cyetrw Onewpte - O* Brtirg, Px GO, OOO. 

صفحه 54:
)ده و ال ‎Vee‏ + © @evehit Cua sire wy XOL dag, eve witout OTD HB Orabats: © Onis brokeo ‏هه سود توص بو با ما و‎ © Quen stop ‏ات ,عم چاه ای واه سود هم‎ rae be su Ocsdner Cyetrw Onewpte - O* Brtirg, Px GO, OOO. woe ©Sbervehnts, Cork ced Cnakershe 

صفحه 55:
+ Drpptay XOL Orta to ‏تا‎ 0 Relate pera Bre each ‏تام ما ان و بو‎ © ard aire ‏صا‎ otore a uci id Por euch ebro © © rebtion aidbnte correspradny ty fark elect crib te © @ pore _H tthe to heey track oP porect elewet > Oe the tee represestaios ١ Poston kPorwaton (chi) con be store io ۲ ۵۱ ‏اه ما ما وه ی رای مج با تمه‎ © Por texted subeleweds, store ‏اس اجه با بط‎ ‏سم پیب با‎ cam ‏و‎ bre rk he os ‏یط‎ ‎Bl Cibebweds thot oo ‏جاب موه وه او و ی و‎ © ‏سمل‎ to koodlog oP ‏حول ۲) شمه ارت واه لصامطمی‎ to ‏ال‎ Ocsdner Cyetrw Onewpte - O* Brtirg, Px GO, OOO. woo ©Sbervehnts, Cork ced Cnakershe 

صفحه 56:
+ Ovrieg XO Orta a Reksoud ‏سس‎ § Publshiey: provess oP coaverteg retaticod date to ot XOL Porat ۲ ‏لمات‎ process oP coaveriey ot XL doranvedt tei a get oP tuples to be ‏وا لو‎ vo or wore rekiccs © XOL-coubled database systews support cuicwoted ‏الم‎ oad shredders © Gowe stews oP Per oatve steroge oF XL data usta the xen dats ye. (Gpertd toterod dota structures ced todices are used Por ef Pinteamy Ocsdner Cyetrw Onewpte - O* Brtirg, Px GO, OOO. woo ©Sbervehnts, Cork ced Cnakershe 

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را + © Dew standard GGL exteosiva that glows ‏ای بل( تیه اه مش‎ © Gack pupa tuple & wopped tp oo XOL elewet row له میت ریت <جاه سس > 0400 حووامسم مه > ح > مسصسو) ح > > 000 سل <ييوم|> 2 wore rows Phere ore wore DI ‏جعاصب!‎ ‏حسجويول>‎ ‎<a> Ocsdner Cyetrw Onewpte - O* Brtirg, Px GO, OOO. wor ©Sbervehnts, Cork ced Cnakershe 

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تسده نوی + اه با( میس ‎ovbbwedt‏ © اه من اد ۲ seen eoecedt are ‏ی مه مه و پر هار‎ ‏اس ساسا سم ماما‎ robbed (aoe "kee", fukn) امه مما موه ‎Px GO, OOO.‏ بسع *© - مرجي س9 لوق 

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Chapter 10: XML Database System Concepts ©Silberschatz, Korth and Sudarshan See www.db-book.com for conditions on re-use XML  Structure of XML Data  XML Document Schema  Querying and Transformation  Application Program Interfaces to XML  Storage of XML Data  XML Applications Database System Concepts - 5th Edition, Aug 22, 2005. 10.2 ©Silberschatz, Korth and Sudarshan Introduction  XML: Extensible Markup Language  Defined by the WWW Consortium (W3C)  Derived from SGML (Standard Generalized Markup Language), but simpler to use than SGML  Documents have tags giving extra information about sections of the document   E.g. <title> XML </title> <slide> Introduction …</slide> Extensible, unlike HTML  Users can add new tags, and separately specify how the tag should be handled for display Database System Concepts - 5th Edition, Aug 22, 2005. 10.3 ©Silberschatz, Korth and Sudarshan XML Introduction (Cont.)  The ability to specify new tags, and to create nested tag structures make XML a great way to exchange data, not just documents.   Much of the use of XML has been in data exchange applications, not as a replacement for HTML Tags make data (relatively) self-documenting  E.g. <bank> <account> <account_number> A-101 </account_number> <branch_name> Downtown </branch_name> <balance> 500 </balance> </account> <depositor> <account_number> A-101 </account_number> <customer_name> Johnson </customer_name> </depositor> </bank> Database System Concepts - 5th Edition, Aug 22, 2005. 10.4 ©Silberschatz, Korth and Sudarshan XML: Motivation  Data interchange is critical in today’s networked world  Examples:  Banking: funds transfer  Order processing (especially inter-company orders)  Scientific data – Chemistry: ChemML, … – Genetics:  BSML (Bio-Sequence Markup Language), … Paper flow of information between organizations is being replaced by electronic flow of information  Each application area has its own set of standards for representing information  XML has become the basis for all new generation data interchange formats Database System Concepts - 5th Edition, Aug 22, 2005. 10.5 ©Silberschatz, Korth and Sudarshan XML Motivation (Cont.)   Earlier generation formats were based on plain text with line headers indicating the meaning of fields  Similar in concept to email headers  Does not allow for nested structures, no standard “type” language  Tied too closely to low level document structure (lines, spaces, etc) Each XML based standard defines what are valid elements, using     DTD (Document Type Descriptors)  XML Schema Plus textual descriptions of the semantics XML allows new tags to be defined as required   XML type specification languages to specify the syntax However, this may be constrained by DTDs A wide variety of tools is available for parsing, browsing and querying XML documents/data Database System Concepts - 5th Edition, Aug 22, 2005. 10.6 ©Silberschatz, Korth and Sudarshan Comparison with Relational Data  Inefficient: tags, which in effect represent schema information, are repeated  Better than relational tuples as a data-exchange format  Unlike relational tuples, XML data is self-documenting due to presence of tags  Non-rigid format: tags can be added  Allows nested structures  Wide acceptance, not only in database systems, but also in browsers, tools, and applications Database System Concepts - 5th Edition, Aug 22, 2005. 10.7 ©Silberschatz, Korth and Sudarshan Structure of XML Data  Tag: label for a section of data  Element: section of data beginning with <tagname> and ending with matching </tagname>  Elements must be properly nested  Proper nesting   Improper nesting    <account> … <balance> …. </balance> </account> <account> … <balance> …. </account> </balance> Formally: every start tag must have a unique matching end tag, that is in the context of the same parent element. Every document must have a single top-level element Database System Concepts - 5th Edition, Aug 22, 2005. 10.8 ©Silberschatz, Korth and Sudarshan Example of Nested Elements <bank-1> <customer> <customer_name> Hayes </customer_name> <customer_street> Main </customer_street> <customer_city> Harrison </customer_city> <account> <account_number> A-102 </account_number> <branch_name> Perryridge </branch_name> <balance> 400 </balance> </account> <account> … </account> </customer> . . </bank-1> Database System Concepts - 5th Edition, Aug 22, 2005. 10.9 ©Silberschatz, Korth and Sudarshan Motivation for Nesting  Nesting of data is useful in data transfer    Example: elements representing customer_id, customer_name, and address nested within an order element Nesting is not supported, or discouraged, in relational databases  With multiple orders, customer name and address are stored redundantly  normalization replaces nested structures in each order by foreign key into table storing customer name and address information  Nesting is supported in object-relational databases But nesting is appropriate when transferring data  External application does not have direct access to data referenced by a foreign key Database System Concepts - 5th Edition, Aug 22, 2005. 10.10 ©Silberschatz, Korth and Sudarshan Structure of XML Data (Cont.)  Mixture of text with sub-elements is legal in XML.  Example: <account> This account is seldom used any more. <account_number> A-102</account_number> <branch_name> Perryridge</branch_name> <balance>400 </balance> </account>  Useful for document markup, but discouraged for data representation Database System Concepts - 5th Edition, Aug 22, 2005. 10.11 ©Silberschatz, Korth and Sudarshan Attributes  Elements can have attributes <account acct-type = “checking” > <account_number> A-102 </account_number> <branch_name> Perryridge </branch_name> <balance> 400 </balance> </account>  Attributes are specified by name=value pairs inside the starting tag of an element  An element may have several attributes, but each attribute name can only occur once <account acct-type = “checking” monthly-fee=“5”> Database System Concepts - 5th Edition, Aug 22, 2005. 10.12 ©Silberschatz, Korth and Sudarshan Attributes vs. Subelements  Distinction between subelement and attribute  In the context of documents, attributes are part of markup, while subelement contents are part of the basic document contents  In the context of data representation, the difference is unclear and may be confusing  Same information can be represented in two ways – <account account_number = “A-101”> …. </account> – <account> <account_number>A-101</account_number> … </account>  Suggestion: use attributes for identifiers of elements, and use subelements for contents Database System Concepts - 5th Edition, Aug 22, 2005. 10.13 ©Silberschatz, Korth and Sudarshan Namespaces  XML data has to be exchanged between organizations  Same tag name may have different meaning in different organizations, causing confusion on exchanged documents  Specifying a unique string as an element name avoids confusion  Better solution: use unique-name:element-name  Avoid using long unique names all over document by using XML Namespaces <bank Xmlns:FB=‘http://www.FirstBank.com’> … <FB:branch> <FB:branchname>Downtown</FB:branchname> <FB:branchcity> Brooklyn </FB:branchcity> </FB:branch> … </bank> Database System Concepts - 5th Edition, Aug 22, 2005. 10.14 ©Silberschatz, Korth and Sudarshan More on XML Syntax  Elements without subelements or text content can be abbreviated by ending the start tag with a /> and deleting the end tag   <account number=“A-101” branch=“Perryridge” balance=“200 /> To store string data that may contain tags, without the tags being interpreted as subelements, use CDATA as below  <![CDATA[<account> … </account>]]> Here, <account> and </account> are treated as just strings CDATA stands for “character data” Database System Concepts - 5th Edition, Aug 22, 2005. 10.15 ©Silberschatz, Korth and Sudarshan XML Document Schema  Database schemas constrain what information can be stored, and the data types of stored values  XML documents are not required to have an associated schema  However, schemas are very important for XML data exchange   Otherwise, a site cannot automatically interpret data received from another site Two mechanisms for specifying XML schema  Document Type Definition (DTD)   Widely used XML Schema  Newer, increasing use Database System Concepts - 5th Edition, Aug 22, 2005. 10.16 ©Silberschatz, Korth and Sudarshan Document Type Definition (DTD)  The type of an XML document can be specified using a DTD  DTD constraints structure of XML data   What elements can occur  What attributes can/must an element have  What subelements can/must occur inside each element, and how many times. DTD does not constrain data types   All values represented as strings in XML DTD syntax  <!ELEMENT element (subelements-specification) >  <!ATTLIST element (attributes) > Database System Concepts - 5th Edition, Aug 22, 2005. 10.17 ©Silberschatz, Korth and Sudarshan Element Specification in DTD  Subelements can be specified as  names of elements, or  #PCDATA (parsed character data), i.e., character strings  EMPTY (no subelements) or ANY (anything can be a subelement)  Example <! ELEMENT depositor (customer_name account_number)> <! ELEMENT customer_name (#PCDATA)> <! ELEMENT account_number (#PCDATA)>  Subelement specification may have regular expressions <!ELEMENT bank ( ( account | customer | depositor)+)>  Notation: – “|” - alternatives – “+” - 1 or more occurrences – “*” - 0 or more occurrences Database System Concepts - 5th Edition, Aug 22, 2005. 10.18 ©Silberschatz, Korth and Sudarshan Bank DTD <!DOCTYPE bank [ <!ELEMENT bank ( ( account | customer | depositor)+)> <!ELEMENT account (account_number branch_name balance)> <! ELEMENT customer(customer_name customer_street customer_city)> <! ELEMENT depositor (customer_name account_number)> <! ELEMENT account_number (#PCDATA)> <! ELEMENT branch_name (#PCDATA)> <! ELEMENT balance(#PCDATA)> <! ELEMENT customer_name(#PCDATA)> <! ELEMENT customer_street(#PCDATA)> <! ELEMENT customer_city(#PCDATA)> ]> Database System Concepts - 5th Edition, Aug 22, 2005. 10.19 ©Silberschatz, Korth and Sudarshan Attribute Specification in DTD  Attribute specification : for each attribute  Name  Type of attribute  CDATA  ID (identifier) or IDREF (ID reference) or IDREFS (multiple IDREFs) –   more on this later Whether  mandatory (#REQUIRED)  has a default value (value),  or neither (#IMPLIED) Examples  <!ATTLIST account acct-type CDATA “checking”>  <!ATTLIST customer customer_id ID # REQUIRED accounts IDREFS # REQUIRED > Database System Concepts - 5th Edition, Aug 22, 2005. 10.20 ©Silberschatz, Korth and Sudarshan IDs and IDREFs  An element can have at most one attribute of type ID  The ID attribute value of each element in an XML document must be distinct  Thus the ID attribute value is an object identifier  An attribute of type IDREF must contain the ID value of an element in the same document  An attribute of type IDREFS contains a set of (0 or more) ID values. Each ID value must contain the ID value of an element in the same document Database System Concepts - 5th Edition, Aug 22, 2005. 10.21 ©Silberschatz, Korth and Sudarshan Bank DTD with Attributes  Bank DTD with ID and IDREF attribute types. <!DOCTYPE bank-2[ <!ELEMENT account (branch, balance)> <!ATTLIST account account_number ID # REQUIRED owners IDREFS # REQUIRED> <!ELEMENT customer(customer_name, customer_street, customer_city)> <!ATTLIST customer customer_id ID # REQUIRED accounts IDREFS # REQUIRED> … declarations for branch, balance, customer_name, customer_street and customer_city ]> Database System Concepts - 5th Edition, Aug 22, 2005. 10.22 ©Silberschatz, Korth and Sudarshan XML data with ID and IDREF attributes <bank-2> <account account_number=“A-401” owners=“C100 C102”> <branch_name> Downtown </branch_name> <balance> 500 </balance> </account> <customer customer_id=“C100” accounts=“A-401”> <customer_name>Joe </customer_name> <customer_street> Monroe </customer_street> <customer_city> Madison</customer_city> </customer> <customer customer_id=“C102” accounts=“A-401 A-402”> <customer_name> Mary </customer_name> <customer_street> Erin </customer_street> <customer_city> Newark </customer_city> </customer> </bank-2> Database System Concepts - 5th Edition, Aug 22, 2005. 10.23 ©Silberschatz, Korth and Sudarshan Limitations of DTDs  No typing of text elements and attributes   All values are strings, no integers, reals, etc. Difficult to specify unordered sets of subelements  Order is usually irrelevant in databases (unlike in the document-layout environment from which XML evolved)  (A | B)* allows specification of an unordered set, but   Cannot ensure that each of A and B occurs only once IDs and IDREFs are untyped  The owners attribute of an account may contain a reference to another account, which is meaningless  owners attribute should ideally be constrained to refer to customer elements Database System Concepts - 5th Edition, Aug 22, 2005. 10.24 ©Silberschatz, Korth and Sudarshan XML Schema  XML Schema is a more sophisticated schema language which addresses the drawbacks of DTDs. Supports  Typing of values  E.g. integer, string, etc  Also, constraints on min/max values  User-defined, comlex types  Many more features, including   uniqueness and foreign key constraints, inheritance XML Schema is itself specified in XML syntax, unlike DTDs  More-standard representation, but verbose  XML Scheme is integrated with namespaces  BUT: XML Schema is significantly more complicated than DTDs. Database System Concepts - 5th Edition, Aug 22, 2005. 10.25 ©Silberschatz, Korth and Sudarshan XML Schema Version of Bank DTD <xs:schema xmlns:xs=http://www.w3.org/2001/XMLSchema> <xs:element name=“bank” type=“BankType”/> <xs:element name=“account”> <xs:complexType> <xs:sequence> <xs:element name=“account_number” type=“xs:string”/> <xs:element name=“branch_name” type=“xs:string”/> <xs:element name=“balance” type=“xs:decimal”/> </xs:squence> </xs:complexType> </xs:element> ….. definitions of customer and depositor …. <xs:complexType name=“BankType”> <xs:squence> <xs:element ref=“account” minOccurs=“0” maxOccurs=“unbounded”/> <xs:element ref=“customer” minOccurs=“0” maxOccurs=“unbounded”/> <xs:element ref=“depositor” minOccurs=“0” maxOccurs=“unbounded”/> </xs:sequence> </xs:complexType> </xs:schema> Database System Concepts - 5th Edition, Aug 22, 2005. 10.26 ©Silberschatz, Korth and Sudarshan XML Schema Version of Bank DTD  Choice of “xs:” was ours -- any other namespace prefix could be chosen  Element “bank” has type “BankType”, which is defined separately   xs:complexType is used later to create the named complex type “BankType” Element “account” has its type defined in-line Database System Concepts - 5th Edition, Aug 22, 2005. 10.27 ©Silberschatz, Korth and Sudarshan More features of XML Schema  Attributes specified by xs:attribute tag:  <xs:attribute name = “account_number”/>  adding the attribute use = “required” means value must be specified  Key constraint: “account numbers form a key for account elements under the root bank element: <xs:key name = “accountKey”> <xs:selector xpath = “]bank/account”/> <xs:field xpath = “account_number”/> <\xs:key>  Foreign key constraint from depositor to account: <xs:keyref name = “depositorAccountKey” refer=“accountKey”> <xs:selector xpath = “]bank/account”/> <xs:field xpath = “account_number”/> <\xs:keyref> Database System Concepts - 5th Edition, Aug 22, 2005. 10.28 ©Silberschatz, Korth and Sudarshan Querying and Transforming XML Data  Translation of information from one XML schema to another  Querying on XML data  Above two are closely related, and handled by the same tools  Standard XML querying/translation languages  XPath   XSLT   Simple language consisting of path expressions Simple language designed for translation from XML to XML and XML to HTML XQuery  An XML query language with a rich set of features Database System Concepts - 5th Edition, Aug 22, 2005. 10.29 ©Silberschatz, Korth and Sudarshan Tree Model of XML Data  Query and transformation languages are based on a tree model of XML data  An XML document is modeled as a tree, with nodes corresponding to elements and attributes  Element nodes have child nodes, which can be attributes or subelements  Text in an element is modeled as a text node child of the element  Children of a node are ordered according to their order in the XML document  Element and attribute nodes (except for the root node) have a single parent, which is an element node  The root node has a single child, which is the root element of the document Database System Concepts - 5th Edition, Aug 22, 2005. 10.30 ©Silberschatz, Korth and Sudarshan XPath  XPath is used to address (select) parts of documents using path expressions  A path expression is a sequence of steps separated by “/”  Think of file names in a directory hierarchy  Result of path expression: set of values that along with their containing elements/attributes match the specified path  E.g. /bank-2/customer/customer_name evaluated on the bank-2 data we saw earlier returns <customer_name>Joe</customer_name> <customer_name>Mary</customer_name>  E.g. /bank-2/customer/customer_name/text( ) returns the same names, but without the enclosing tags Database System Concepts - 5th Edition, Aug 22, 2005. 10.31 ©Silberschatz, Korth and Sudarshan XPath (Cont.)  The initial “/” denotes root of the document (above the top-level tag)  Path expressions are evaluated left to right   Selection predicates may follow any step in a path, in [ ]   Each step operates on the set of instances produced by the previous step E.g. /bank-2/account[balance > 400]  returns account elements with a balance value greater than 400  /bank-2/account[balance] returns account elements containing a balance subelement Attributes are accessed using “@”  E.g. /bank-2/account[balance > 400]/@account_number   returns the account numbers of accounts with balance > 400 IDREF attributes are not dereferenced automatically (more on this later) Database System Concepts - 5th Edition, Aug 22, 2005. 10.32 ©Silberschatz, Korth and Sudarshan Functions in XPath  XPath provides several functions  The function count() at the end of a path counts the number of elements in the set generated by the path   E.g. /bank-2/account[count(./customer) > 2] – Returns accounts with > 2 customers Also function for testing position (1, 2, ..) of node w.r.t. siblings  Boolean connectives and and or and function not() can be used in predicates  IDREFs can be referenced using function id()  id() can also be applied to sets of references such as IDREFS and even to strings containing multiple references separated by blanks  E.g. /bank-2/account/id(@owner)  returns all customers referred to from the owners attribute of account elements. Database System Concepts - 5th Edition, Aug 22, 2005. 10.33 ©Silberschatz, Korth and Sudarshan More XPath Features  Operator “|” used to implement union   E.g. /bank-2/account/id(@owner) | /bank-2/loan/id(@borrower)  Gives customers with either accounts or loans  However, “|” cannot be nested inside other operators. “//” can be used to skip multiple levels of nodes  E.g. /bank-2//customer_name    finds any customer_name element anywhere under the /bank-2 element, regardless of the element in which it is contained. A step in the path can go to parents, siblings, ancestors and descendants of the nodes generated by the previous step, not just to the children  “//”, described above, is a short from for specifying “all descendants”  “..” specifies the parent. doc(name) returns the root of a named document Database System Concepts - 5th Edition, Aug 22, 2005. 10.34 ©Silberschatz, Korth and Sudarshan XQuery  XQuery is a general purpose query language for XML data  Currently being standardized by the World Wide Web Consortium (W3C)  The textbook description is based on a January 2005 draft of the standard. The final version may differ, but major features likely to stay unchanged.  XQuery is derived from the Quilt query language, which itself borrows from SQL, XQL and XML-QL  XQuery uses a for … let … where … order by …result … syntax for  SQL from where  SQL where order by  SQL order by result  SQL select let allows temporary variables, and has no equivalent in SQL Database System Concepts - 5th Edition, Aug 22, 2005. 10.35 ©Silberschatz, Korth and Sudarshan FLWOR Syntax in XQuery  For clause uses XPath expressions, and variable in for clause ranges over values in the set returned by XPath  Simple FLWOR expression in XQuery   find all accounts with balance > 400, with each result enclosed in an <account_number> .. </account_number> tag for $x in /bank-2/account let $acctno := $x/@account_number where $x/balance > 400 return <account_number> { $acctno } </account_number>  Items in the return clause are XML text unless enclosed in {}, in which case they are evaluated Let clause not really needed in this query, and selection can be done In XPath. Query can be written as: for $x in /bank-2/account[balance>400] return <account_number> { $x/@account_number } </account_number> Database System Concepts - 5th Edition, Aug 22, 2005. 10.36 ©Silberschatz, Korth and Sudarshan Joins  Joins are specified in a manner very similar to SQL for $a in /bank/account, $c in /bank/customer, $d in /bank/depositor where $a/account_number = $d/account_number and $c/customer_name = $d/customer_name return <cust_acct> { $c $a } </cust_acct>  The same query can be expressed with the selections specified as XPath selections: for $a in /bank/account $c in /bank/customer $d in /bank/depositor[ account_number = $a/account_number and customer_name = $c/customer_name ] return <cust_acct> { $c $a } </cust_acct> Database System Concepts - 5th Edition, Aug 22, 2005. 10.37 ©Silberschatz, Korth and Sudarshan Nested Queries  The following query converts data from the flat structure for bank information into the nested structure used in bank-1 <bank-1> { for $c in /bank/customer return <customer> { $c/* } { for $d in /bank/depositor[customer_name = $c/customer_name], $a in /bank/account[account_number=$d/account_number] return $a } </customer> } </bank-1>  $c/* denotes all the children of the node to which $c is bound, without the enclosing toplevel tag  $c/text() gives text content of an element without any subelements / tags Database System Concepts - 5th Edition, Aug 22, 2005. 10.38 ©Silberschatz, Korth and Sudarshan Sorting in XQuery  The order by clause can be used at the end of any expression. E.g. to return customers sorted by name for $c in /bank/customer order by $c/customer_name return <customer> { $c/* } </customer>  Use order by $c/customer_name to sort in descending order  Can sort at multiple levels of nesting (sort by customer_name, and by account_number within each customer) <bank-1> { for $c in /bank/customer order by $c/customer_name return <customer> { $c/* } { for $d in /bank/depositor[customer_name=$c/customer_name], $a in /bank/account[account_number=$d/account_number] } order by $a/account_number return <account> $a/* </account> </customer> } </bank-1> Database System Concepts - 5th Edition, Aug 22, 2005. 10.39 ©Silberschatz, Korth and Sudarshan Functions and Other XQuery Features  User defined functions with the type system of XMLSchema function balances(xs:string $c) returns list(xs:decimal*) { for $d in /bank/depositor[customer_name = $c], $a in /bank/account[account_number = $d/account_number] return $a/balance }  Types are optional for function parameters and return values  The * (as in decimal*) indicates a sequence of values of that type  Universal and existential quantification in where clause predicates   some $e in path satisfies P  every $e in path satisfies P XQuery also supports If-then-else clauses Database System Concepts - 5th Edition, Aug 22, 2005. 10.40 ©Silberschatz, Korth and Sudarshan XSLT  A stylesheet stores formatting options for a document, usually separately from document  E.g. an HTML style sheet may specify font colors and sizes for headings, etc.  The XML Stylesheet Language (XSL) was originally designed for generating HTML from XML  XSLT is a general-purpose transformation language   Can translate XML to XML, and XML to HTML XSLT transformations are expressed using rules called templates  Templates combine selection using XPath with construction of results Database System Concepts - 5th Edition, Aug 22, 2005. 10.41 ©Silberschatz, Korth and Sudarshan XSLT Templates  Example of XSLT template with match and select part <xsl:template match=“/bank-2/customer”> <xsl:value-of select=“customer_name”/>     </xsl:template> <xsl:template match=“*”/> The match attribute of xsl:template specifies a pattern in XPath Elements in the XML document matching the pattern are processed by the actions within the xsl:template element  xsl:value-of selects (outputs) specified values (here, customer_name) For elements that do not match any template  Attributes and text contents are output as is  Templates are recursively applied on subelements The <xsl:template match=“*”/> template matches all elements that do not match any other template   Used to ensure that their contents do not get output. If an element matches several templates, only one is used based on a complex priority scheme/user-defined priorities Database System Concepts - 5th Edition, Aug 22, 2005. 10.42 ©Silberschatz, Korth and Sudarshan Creating XML Output Any text or tag in the XSL stylesheet that is not in the xsl namespace is output as is  E.g. to wrap results in new XML elements. <xsl:template match=“/bank-2/customer”>  <customer> <xsl:value-of select=“customer_name”/> </customer> </xsl;template> <xsl:template match=“*”/>  Example output: <customer> Joe </customer> <customer> Mary </customer> Database System Concepts - 5th Edition, Aug 22, 2005. 10.43 ©Silberschatz, Korth and Sudarshan Creating XML Output (Cont.) Note: Cannot directly insert a xsl:value-of tag inside another tag  E.g. cannot create an attribute for <customer> in the previous example by directly using xsl:value-of  XSLT provides a construct xsl:attribute to handle this situation  xsl:attribute adds attribute to the preceding element  E.g. <customer> <xsl:attribute name=“customer_id”> <xsl:value-of select = “customer_id”/> </xsl:attribute> </customer> results in output of the form <customer customer_id=“….”> ….  xsl:element is used to create output elements with computed names  Database System Concepts - 5th Edition, Aug 22, 2005. 10.44 ©Silberschatz, Korth and Sudarshan Structural Recursion  Template action can apply templates recursively to the contents of a matched element <xsl:template match=“/bank”> <customers> <xsl:template apply-templates/> </customers > </xsl:template> <xsl:template match=“/customer”> <customer> <xsl:value-of select=“customer_name”/> </customer> </xsl:template> <xsl:template match=“*”/>  Example output: <customers> <customer> John </customer> <customer> Mary </customer> </customers> Database System Concepts - 5th Edition, Aug 22, 2005. 10.45 ©Silberschatz, Korth and Sudarshan Joins in XSLT XSLT keys allow elements to be looked up (indexed) by values of subelements or attributes  Keys must be declared (with a name) and, the key() function can then be used for lookup. E.g. <xsl:key name=“acctno” match=“account” use=“account_number”/> <xsl:value-of select=key(“acctno”, “A-101”)  Keys permit (some) joins to be expressed in XSLT <xsl:key name=“acctno” match=“account” use=“account_number”/> <xsl:key name=“custno” match=“customer” use=“customer_name”/> <xsl:template match=“depositor”> <cust_acct> <xsl:value-of select=key(“custno”, “customer_name”)/> <xsl:value-of select=key(“acctno”, “account_number”)/> </cust_acct> </xsl:template> <xsl:template match=“*”/>  Database System Concepts - 5th Edition, Aug 22, 2005. 10.46 ©Silberschatz, Korth and Sudarshan Sorting in XSLT  Using an xsl:sort directive inside a template causes all elements matching the template to be sorted  Sorting is done before applying other templates <xsl:template match=“/bank”> <xsl:apply-templates select=“customer”> <xsl:sort select=“customer_name”/> </xsl:apply-templates> </xsl:template> <xsl:template match=“customer”> <customer> <xsl:value-of select=“customer_name”/> <xsl:value-of select=“customer_street”/> <xsl:value-of select=“customer_city”/> </customer> <xsl:template> <xsl:template match=“*”/> Database System Concepts - 5th Edition, Aug 22, 2005. 10.47 ©Silberschatz, Korth and Sudarshan Application Program Interface  There are two standard application program interfaces to XML data:  SAX (Simple API for XML)  Based on parser model, user provides event handlers for parsing events – E.g. start of element, end of element – Not suitable for database applications  DOM (Document Object Model)  XML data is parsed into a tree representation  Variety of functions provided for traversing the DOM tree  E.g.: Java DOM API provides Node class with methods getParentNode( ), getFirstChild( ), getNextSibling( ) getAttribute( ), getData( ) (for text node) getElementsByTagName( ), …  Also provides functions for updating DOM tree Database System Concepts - 5th Edition, Aug 22, 2005. 10.48 ©Silberschatz, Korth and Sudarshan Storage of XML Data  XML data can be stored in  Non-relational data stores  Flat files – Natural for storing XML – But has all problems discussed in Chapter 1 (no concurrency, no recovery, …)  XML database – Database built specifically for storing XML data, supporting DOM model and declarative querying – Currently no commercial-grade systems  Relational databases  Data must be translated into relational form  Advantage: mature database systems  Disadvantages: overhead of translating data and queries Database System Concepts - 5th Edition, Aug 22, 2005. 10.49 ©Silberschatz, Korth and Sudarshan Storage of XML in Relational Databases  Alternatives:  String Representation  Tree Representation  Map to relations Database System Concepts - 5th Edition, Aug 22, 2005. 10.50 ©Silberschatz, Korth and Sudarshan String Representation  Store each top level element as a string field of a tuple in a relational database  Use a single relation to store all elements, or  Use a separate relation for each top-level element type  E.g. account, customer, depositor relations – Each with a string-valued attribute to store the element  Indexing:  Store values of subelements/attributes to be indexed as extra fields of the relation, and build indices on these fields   E.g. customer_name or account_number Some database systems support function indices, which use the result of a function as the key value.  The function should return the value of the required subelement/attribute Database System Concepts - 5th Edition, Aug 22, 2005. 10.51 ©Silberschatz, Korth and Sudarshan String Representation (Cont.)  Benefits:  Can store any XML data even without DTD  As long as there are many top-level elements in a document, strings are small compared to full document   Allows fast access to individual elements. Drawback: Need to parse strings to access values inside the elements  Parsing is slow. Database System Concepts - 5th Edition, Aug 22, 2005. 10.52 ©Silberschatz, Korth and Sudarshan Tree Representation  Tree representation: model XML data as tree and store using relations nodes(id, type, label, value) child (child_id, parent_id) bank (id:1) customer (id:2) account (id: 5) customer_name (id: 3) account_number (id: 7)  Each element/attribute is given a unique identifier  Type indicates element/attribute  Label specifies the tag name of the element/name of attribute  Value is the text value of the element/attribute  The relation child notes the parent-child relationships in the tree  Can add an extra attribute to child to record ordering of children Database System Concepts - 5th Edition, Aug 22, 2005. 10.53 ©Silberschatz, Korth and Sudarshan Tree Representation (Cont.)  Benefit: Can store any XML data, even without DTD  Drawbacks:  Data is broken up into too many pieces, increasing space overheads  Even simple queries require a large number of joins, which can be slow Database System Concepts - 5th Edition, Aug 22, 2005. 10.54 ©Silberschatz, Korth and Sudarshan Mapping XML Data to Relations    Relation created for each element type whose schema is known:  An id attribute to store a unique id for each element  A relation attribute corresponding to each element attribute  A parent_id attribute to keep track of parent element  As in the tree representation  Position information (ith child) can be store too All subelements that occur only once can become relation attributes  For text-valued subelements, store the text as attribute value  For complex subelements, can store the id of the subelement Subelements that can occur multiple times represented in a separate table  Similar to handling of multivalued attributes when converting ER diagrams to tables Database System Concepts - 5th Edition, Aug 22, 2005. 10.55 ©Silberschatz, Korth and Sudarshan Storing XML Data in Relational Systems  Publishing: process of converting relational data to an XML format  Shredding: process of converting an XML document into a set of tuples to be inserted into one or more relations  XML-enabled database systems support automated publishing and shredding  Some systems offer native storage of XML data using the xml data type. Special internal data structures and indices are used for efficiency Database System Concepts - 5th Edition, Aug 22, 2005. 10.56 ©Silberschatz, Korth and Sudarshan SQL/XML  New standard SQL extension that allows creation of nested XML output  Each output tuple is mapped to an XML element row <bank> <account> <row> <account_number> A-101 </account_number> <branch_name> Downtown </branch_name> <balance> 500 </balance> </row> …. more rows if there are more output tuples … </account> </bank> Database System Concepts - 5th Edition, Aug 22, 2005. 10.57 ©Silberschatz, Korth and Sudarshan SQL Extensions  xmlelement creates XML elements  xmlattributes creates attributes select xmlelement (name “account, xmlattributes (account_number as account_number), xmlelement (name “branch_name”, branch_name), xmlelement (name “balance”, balance)) from account Database System Concepts - 5th Edition, Aug 22, 2005. 10.58 ©Silberschatz, Korth and Sudarshan Web Services   The Simple Object Access Protocol (SOAP) standard:  Invocation of procedures across applications with distinct databases  XML used to represent procedure input and output A Web service is a site providing a collection of SOAP procedures  Described using the Web Services Description Language (WSDL)  Directories of Web services are described using the Universal Description, Discovery, and Integration (UDDI) standard Database System Concepts - 5th Edition, Aug 22, 2005. 10.59 ©Silberschatz, Korth and Sudarshan