Enumerating XML Data for Dynamic Updating

Transcription

1 Eumeratg XML Data for Dyamc Updatg Lau Ho Kt ad Vcet Ng Departmet of Computg, The Hog Kog Polytechc Uversty, Hug Hom, Kowloo, Hog Kog Abstract I ths paper, a ew mappg model, called -INode, s preseted ad t s used to support dyamc updatg of XML data flexbly. Oe ey feature of -INode s the use of mult-dmesoal umberg scheme to verfy the cotamet relatoshps betwee XML odes The prelmary expermets show that -INode supports dyamc updatg of XML documets effectvely ad effcetly.. Keywords: XML, database, updatg. Itroducto There are dfferet mappg models to store ad maage XML data usg relatoal databases. The two geeral approaches are the structure-mappg approach ad the model-mappg approach as metoed by YoshKawa, M.A. T. (). The desg of database schemas of the structure-mappg approach s based o the Documet Type Defto (DTD) of XML documets. Mostly, they use the structural formato to desg the database schemas. Examples clude STORED (Deutsch, A., Feradez, M., ad Sucu, D. 999). ad XStorM (Wag, W.Q., Lee, M.L., Oo, B.C., ad Ta, K.-L. ). However, ths desg s ot sutable for dyamc structure data because dfferet structures of XML documets have dfferet database schemas. Ule structure-mappg approach, the database schemas of the model-mappg approach are fxed for dfferet structures of XML documets. Examples clude Edge (Florescu, D. ad Kossma, D. 999), XRel (YoshKawa, M.A. T. ), XParet (Jag, H., Lu, H., Wag, W., ad Yu, J.X. ), XNode (Ng, V., Lau, H.K., ad Chu, S.W ), INode (Lau, H.K. ad Ng, V 3).ad INode* (Lau, H.K. ad Ng, V. 4), It s capable to support dyamc structure data, as o structural formato s requred to desg the database schemas. Therefore, t s more flexble ad coveet to maage XML documets relatoal databases. To process XML documets, besdes retrevals, three basc operatos should be cluded. They are serto, Copyrght (c) 5, Australa Computer Socety, Ic. Ths paper appeared at the 6th Australasa Database Coferece, Uversty of Newcastle, Newcastle, Australa. Cofereces Research ad Practce Iformato Techology, Vol. 39. H.E. Wllams ad G. Dobbe, Eds. Reproducto for academc, ot-for proft purposes permtted provded ths text s cluded. updatg ad deleto.. However, may mappg methods, these ds of operatos are ot cosdered. I addto, structurally recursve XML queres are a mportat query class that follows the structure of XML data. I Par, C.-W., M, J.-K., ad Chug, C.-W. (), the authors defed structurally recursve query as a query volves a acestor-descedat relatoshp ( // ), a flterg wth acestor-descedat relatoshps, ad fucto calls to user-defed structurally recursve fuctos. Based o several use cases as dscussed Chamberl, D., Fahauser, P., Marchor, M., ad Robe, J. () ad the requremets of XQuery, structurally recursve queres are frequetly used ad they meet dfferet requremets such as abltes to query the XML data wthout owg the logcal structure. For example, the followg query //ttle[//subect busess ] ofte uses to retreve ttle elemets, where subect descedat s busess, regardless of the structure of data ad the locatos of ttle ad subect elemets the data. Ths paper s structured as follows. Secto gves a revew to the related wors model-based mappg ad brefly descrbes INode. We wll dscuss the supports of dyamc XML documets Secto 3. Secto 4 troduces our ew mappg method, -INode. I Secto 5, expermetal results are show. Fally, we coclude our wor Secto 6. Related Wors Edge, XRel, XParet, XNode, INode ad INode* are sx model-mappg approaches for storg dfferet structures of XML documets relatoal databases. Edge stores the XML data graph a sgle table called Edge. Each ode the data graph s assged a sequetal umber. Each tuple the table correspods to a edge the data graph. XRel uses a schema of four tables to store the XML documets. The tables are Path, Elemet, Text ad Attrbute. Each ode has a rego whch s represeted by the start ad ed posto of the correspodg ode the XML documet. By usg the rego, XRel does ot requre recursve queres to verfy the acestor-descedat relatoshp. Istead of usg recursve queres, XRel uses? os to detfy the cotamet relatoshp. However, t s ot effectve to use? os for queres wth more acestor-descedat relatoshps ad o specal dex mechasm, whch supports cotamets, s provded by off-the-self database maagemet systems. XParet uses a four-table schema to store XML data. Istead of usg regos as XRel, XParet uses a table, called DataPath, to mata paret-chld relatoshp. To verfy the acestor-descedat relatoshp, t requres

2 og the DataPath table tself. It uses equos stead of? os, whch are cosdered as more costly tha equos. INode ad INode* uses the cocept of UID, whch s proposed Kha, D.D., M. Yoshawa, ad S. Uemura (), to assg a detfer (d) to each ode a XML documet. It represets a XML documet as a c -ary complete tree where c s the maxmum umber of chld odes of a ode the structure. Gve a ode, the path of wll be deoted as (a, a, a 3,, a ), where s the depth of ad a c. Wth the cocept of UID, for a ode wth UID, the paret s UID of ths ode ca be calculated drectly by Equato (). Furthermore, gve c ad the correspodg path sequece (a, a, a 3,, a ) of a ode, t calculates the ode d usg Equato () (All equatos ca be foud at the Appedx page). Gve the ode ds of ad, where s the acestor of ad the depth dfferece betwee these two odes s d, INode ad INode* cofrm the acestor-descedat relatoshp by calculatos. INode uses a three-table schema. They are Path, Elemet ad Attrbute. The ey feature of INode s that t uses ode ds to mata the paret-chld relatoshp stead of usg rego as XRel or usg aother table as XParet. Ths further reduces the umber of table os whe performg queres wth the paret-chld relatoshp or the acestor-descedat relatoshp. However, t requres recursve queres to retreve the acestor-descedat relatoshp. 3 Dyamc Updatg of XML Documets Three basc operatos are eeded to support dyamc updatg of XML documets. They are serto, modfcato ad deleto. To modfy or delete a ode, t requres locatg the desred ode ad performs modfcato or deleto. The total cost of modfcato (deleto) s the sum of the cost of locatg the desred ode ad the cost to modfy (delete) the ode. Here, these total costs are domated by the costs of locatg the desred ode. Therefore, t s mportat to have a good query performace for the locato step for the modfy ad delete operatos. For the serto of Edge, t requres to locate the paret ode because oe of the database attrbute s the source ID, whch s potg to the paret ode. The t may requre updatg the ordal of the sblg odes. Fally, t serts the ode the Edge table. Ule Edge, XRel uses the cocept of rego to detfy the odes. For every serto, t wll chage the start ad ed postos of exstg odes. Therefore, t requres updatg the start ad ed postos of exstg odes before sertg a ode. As XParet uses a table, DataPath, to mata the paret-chld relatoshp, a ew record of ths table s requred for each serto. It also requres retrevg the paret ode order to get the correspodg Pd of the paret ode. Le Edge, t requres updatg the ordal of the sblg odes whe ecessary. Fally, t serts the ode Elemet table ad a record of paret-chld relatoshp DataPath table. To sert a ode usg INode or INode*, t does ot requre retrevg the paret ode les Edge ad XParet because t uses ode d to mata the paret-chld relatoshp. It calculates the ode d wth path sequece oly. Therefore, t ust serts the ode ad updates the ordal of the sblg odes. However, t has fxed the maxmum umber of chld odes order to calculate the ode d. Ths lmted the umber of odes that ca be serted. 4 -INode A ew mappg method, -INode, s developed to ehace the flexblty to support dyamc updatg of XML documets. I the -INode method, a mult-dmesoal ode d s troduced. The mult-dmesoal ode d eables the ablty to sert ew odes to a ode whe t has c chld odes ad all exstg ode ds are ot to be re-calculated. For ode ds wth dmesos, each dmeso has a par of umbers, (d x, o x ) where? x?. The frst umber s calculated based o the path sequece wth Equato (). The secod umber s the serto order. Therefore, for a ode wth dmesos, the ode d s defed as (d, o, d, o, d 3, o 3,, d, o ). Sce d x s calculated, t s possble that the d x of a ewly serted ode s the same as the d x of a exstg ode. Therefore, the serto order, o x, s troduced to dstgush odes wth the same d x. The serto order s a sequece of umbers startg from zero. For all descedats of a ode that the correspodg serto order s larger tha zero, a ew dmeso s used order to detfy the odes. By usg the mult-dmesoal ode d, -INode ca cotue to sert odes as chld odes to a gve ode whe t has c chld odes. I addto, t does ot requre matag the orgal XML documets. The hadlg of dfferet types of sertos wll be dscussed ext. Case. Isert a chld ode uder a o-full ode. I Fg., sce the umber of chld odes of A s less tha c, B ca use the value of d calculated by Equato (). Hece, the value of the vrtual ode d s ad the ode d of B s (,). Case. Isert a chld ode at the leftmost uder a full ode. I Fg.3, the d of C must be used by aother ode as the umber of chld odes of A s c. Hece, the value of o of C s the cremet of the maxmum value of o amogst the exstg odes wth the same d values. Sce the path sequece of C s (,,), the paret ode d s 3, the d calculated by Equato ( ) s 8, ad the maxmum of o for the odes wth 8 as d s. Hece, the ode d of C s (8,). Case 3. Isert a chld ode at the rghtmost uder a full ode.

3 Smlar to case, there must a ode wth the same d of D exsted, whch s B show Fg. 4. Here, o s used aga to dstgush the odes ad o s assged to a value larger tha c. If the maxmum of the serto order s ot larger tha c, c s used as the value of o stead. I ths case, the d of D s, whch s the same as B whle the maxmum of o for the odes wth as d s. As a result, c wll be the value of o for D, whch s 4. Fally, the ode d of D s (,4). Based o ths assgmet method, the umber of odes that ca be serted at the left -had sde of B s lmted by c. All ode ds are re-calculated whe o of ay ode s equal to c ad a ew ad larger value of c s used to re-calculate the ode ds. Case 4. Isert a chld ode the mddle uder a full ode. I Fg. 5, d of E s the same as that of ode Q, whch s the rght had sde of the ewly serted ode. Suppose the path sequece of ode Q before ay serto s (,, ). After the serto, the path sequece of E s also (,, ). The ds of E ad Q are the same, whch are 9. Therefore, the o s used to dstgush the odes ad the o value of E s the cremet of the maxmum of o of exstg ode wth the same d. I our example, the maxmum of o for the odes wth 9 as d s. Therefore, the o of E s ad the ode d of E s (9,). Fg.. Case Iserto. Fg. 3. Case Iserto.

4 Case 5. Isert a ode F uder ode E where the serto order of ode E s larger tha oe as show Fg. 6. I ths case, the serto of E s smlar to Case 4 ad F s further serted as a chld of E. The path sequece of F s (,,,) ad the calculated d of F s 6 by usg Equato (). However, a ode wth ode d (6,) already exsts, whch s Q, ad the serto order caot be used to detfy these two odes. If the serto order s used, the possble ode d of F becomes (6,). Based o ths assgmet, the paret-chld relatoshps of odes E, F, Q ad R caot be verfed by usg Equato (). It s because Q ca be the paret ode of F ad E ca be the Fg. 4. Case 3 Iserto. paret ode of R by usg Equato (). Therefore, t requres aother way to dstgush F ad R ad the secod dmeso of ode d s used. For all exstg odes, the secod dmeso ode d s assged wth (,). For example, the ode d of E becomes (9,,,). For the ewly serted ode F, the frst dmeso s assged wth (9,), whch s the same as the frst dmeso ode d of ts paret ode. The d of the secod dmeso s the calculated value by Equato (), whch s 6. The serto order of the secod dmeso s zero as o exstg ode wth the same ode d. Fally, the ode d of F s (9,,6,). Fg. 5. Case 4 Iserto.

5 Fg. 6. Case 5 Iserto.,,,,,,,,,, 3,,,,, 4,,,,, 5,,,,, 5,,,,, 6,,,,, 7,,,,, 5,,,,, 5,,,,, 5,,,,,,,,,,,,,,, 5,,,,, 5,,,,,,,,,, 5,,,,4, Fg. 7. A Example of Three Dmeso Node ID. Fg. 7 shows a XML data graph wth three dmesos ode ds assged ad the value of c s three. Accordg to the assgmet of ode ds, ay two odes have paret-chld relatoshp f ad oly f the umbers of dmesos are the same or the dmeso dfferece s oe. Therefore, two cases are cosdered for the verfcato of paret-chld relatoshp. Case A. IDs wth the same umber of o-zeros d x. Cosder the odes 3 ad 3 wth ds (5,,,,,) ad (5,,,,,) as show Fg. 7, respectvely. The ds are dvded to three parts as follow: st part d part 3 rd part 5 5 For the frst part, t requres to verfy that the odes belog to the same sub-tree. Therefore, the ds must be the same for the frst part. For the secod part, the relatoshp s verfed by calculato. Sce the ds are dmesos oly, the thrd parts of them must be zero. I geeral, for dmesos, the paret-chld relatoshp s verfed usg Equato (3), where s the umber of dmesos of the ds. Case B. IDs wth oe dmeso dfferece. Cosder the odes 3 ad 3 wth ds (5,,,,,) ad (5,,,,,) as show Fg. 7, respectvely. The ds are dvded as three parts aga. However, there s o zero d x the d of. The thrd part s spped below. st d 5 5 Le Case, the frst parts of ds are the same order to verfy that the odes are belog to the same sub-tree. Sce there s a dmeso dfferece of the ds, the secod part s requred to verfy two sub-codtos. Oe sub-codto s the odes belog to the same sub-tree. It wors smlarly as the verfcato of the frst part. The other sub-codto s that the paret-chld relatoshp to be verfed. The verfcato of the thrd part s the same as Case. I geeral, for dmesos, the paret-chld relatoshp s

6 verfed usg Equato (3), where s the umber of dmesos of the paret ode d. For the verfcato of acestor-descedat relatoshp, three cases are cosdered. The frst two cases are smlar to the cases of paret-chld relatoshp by replacg the Paret fucto wth Acestor fucto. Aother case s cosdered below. Case 3. IDs wth more tha oe dmeso dfferece. Cosder the odes 3 ad 3 wth ds (5,,,,,) ad (5,,,,,) as show Fg. 7, respectvely. The ds aga are dvded to three parts. However, the o-zero dmeso of 3 s oe ad there s o zero par for the d of 3. The frst ad the thrd part are omtted here. d part 5 5 Let s the umber of o-zero dmesos of ad l s the umber of o-zero dmesos of 3. Wth the secod part, the relatoshp s verfed by calculatos wth dmeso ode d of ad to l dmeso ode ds of 3. For dmesos, the acestor-descedat relatoshp s verfed by Equato (4). 5 Implemetato ad Expermetal Results For the mplemetato of mult-dmesoal ode d, all zero pars of d x ad o x are replaced wth the last o-zero pars. Fg. 7 shows a example wth 3 dmesos. I the fgure, ode (5,,,,,), s represeted as (5,,5,,5,). Ths replacemet ams to elmate the checg of zero pars. For the modfy operato, the ode s selected ad modfed. Smlarly, the ode s selected to perform deleto ad the ode s mared as deleted. I addto, the ode d of the deleted ode s ot used aga for ewly serted odes. I our desg, a database attrbute, Dm, s added to Elemet ad Attrbute table, whch s the umber of dmesos used of the ode d. Fally, -INode adopts a four-table schema. The tables clude Path, Elemet, Attrbute ad Acestor. A database schema example s show Table (foud at the Appedx page). Whe the maxmum sze of a XML fle s avalable, we ca estmate the umber of dmesos eeded but ths s ot ofte provded. To evaluate the query performace of usg -INode, expermetal studes have bee coducted. Edge, XRel, XParet, INode* ad -INode are studed. All expermets were coducted o a 933MHz Petum III wth 56MB RAM, GB hard ds. The RDBMS used was Oracle 9 Eterprse Edto ad the sze of SGA s 37MB. The Bosa Shaespeare collecto () ad the XML bechmar proect () are used as the data sources. For the secod data source, dfferet scale factors are used to geerate the data. Four dfferet szes of data, ow as Set, Set Set 3 ad Set4, are geerated usg the geerator verso.9. Set4 s used to evaluate the support of dyamc updatg of XML documets as show. Table. Table. Data Sets of the XML Bechmar Proect Name Parameters Used Sze (MB) Maxmum depth Set scale factor.5, 5.6 splt Set scale factor.,.3 splt Set3 scale factor.,.8 splt Set4 scale factor..3 As dscussed Secto 3, the performace of modfcato ad deleto s drectly related to the query performace. Therefore, our evaluato wll be focused o serto. I order to have a set of odes for serto, Set4 s dvded to two parts. The frst part s loaded to the database ad ths part s serted aga to evaluate the performace of sertg odes to the loaded data at dfferet locatos. It cludes the frst two hudred chld odes of each paret ode. The secod part cludes the rest of the odes that are ot loaded order to evaluate the performace of appedg odes to the loaded data. Sce XRel s based o the cocept of rego, t requres the orgal XML documets or recostructs the XML fles from relatoal tables to determe ad update the start ad ed postos. Therefore, we studed Edge, XParet ad -INode. For each serto, three methods requre retrevg the paret ode. The serto cost s defed as the sum of query elapsed tme ad the sert elapsed tme. I addto, two query types are used to retreve the paret ode. They are structurally recursve query ad o-structurally recursve query. The umbers of odes that are serted are 5,, ad 4. The average serto cost s tae. The values of c s for -INode wth three dmesos. 5. Storage Usage Fg. 8 shows the storage usage of -INode comparso wth Edge ad XParet. The data loaded s the frst part of Set4. After mplemeted the mult-dmeso ode d, the storage requred of -INode s creased. However, t s lower tha that of XParet.

7 Sze (Mb) Fg.. Average Iserted Cost of Iserto of a Node the Frst Part of Set Query Performace The Bosa Shaespeare collecto s used for the evaluato of query performace. To load the data set of the Bosa Shaespeare collecto, the value of c s 5 wth three dmesos for -INode. The set of queres s show Fg.. -INode XParet Edge Storage Usage Fg. 8. Storage Usage wth -INode, XParet ad Edge. 5. Iserto Performace Fg. 9 ad Fg. show the average serto cost of sertg a ode. The average serto cost s log scale. I most cases, -INode performs smlarly to XParet ad t performs better tha Edge for serto wth structurally recursve queres ad -INode further mproves the performace whe a large umber of odes are serted because t does ot requre usg recursve query. Average Iserto Cost (Log) INode XParet Edge 5 4 Number of Nodes Iserted Fg. 9. Average Iserted Cost of Iserto of a Node the Secod Part of Set4. The query elapsed tmes are show Fg.. Every query s ru te tmes for each method ad the average elapsed tme s tae. -INode performs smlarly to INode* as they use the same calculato to verfy the relatoshps betwee dfferet odes. However, -INode performs ot as well as INode* some cases because more calculatos are used to verfy the relatoshps due to more dmesos. Eve the, ts performace s comparable to XParet ad XRel. 5.4 Scalablty Test: XRel vs XParet vs -INode I the scalablty test, Set, Set ad Set3 of the XML bechmar proect are used. The settgs of -INode to load the data are the same as that of the evaluato of serto performace. Fg. 3 shows the result of the scalablty test of XRel, XParet, INode* ad -INode, respectvely. The query elapsed tme rato s defed as t /t where t s the elapsed tme of a query usg Set ad t s the elapsed tme of the same query usg Set or Set3. By mplemetg the mult-dmeso ode d ad Acestor table, the scalablty of -INode s mproved ad t s superor to XRel ad XParet. QS: QS: QS3: QS4: QS5: QS6: QS7: QS8: QS9: /PLAY/ACT /PLAY/ACT/SCENE/SPEECH/LINE/STAGEDIR //SCENE/TITLE //ACT//TITLE /PLAY/ACT[] (/PLAY/ACT)[]/TITLE /PLAY/ACT/SCENE/SPEECH[SPEAKER 'CURIO'] /PLAY/ACT/SCENE[//SPEAKER 'Steward']/TITLE /PLAY/ACT[//SPEAKER Steward ]//TITLE Average Iserto Cost (Log) Number of Node Iserted -INode XParet Edge Fg.. Queres Used wth the Bosa Shaespeare Collecto.

8 . Fg.. Average Query Elapsed Tme: usg the Bosa Shaespeare Collecto MB.3MB.8MB QB QB QB4 QB8 QB9 QB QB QB3 QB4 (a) Average Query Elapsed Tme Rato for XRel MB.3MB.8MB QB QB QB4 QB8 QB9 QB QB QB3 5.6MB.3MB.8MB QB4 QB QB3 5.6MB.3MB.8MB QB4 (b) Average Query Elapsed Tme Rato for XParet. (d) Average Query Elapsed Tme Rato for -INode. Fg. 5. Scalablty Test wth XRel, XParet, INode ad -INode (c) Query Elapsed Tme Rato for INode*. QB QB QB4 QB8 QB9 QB QB QB3 QB4 QB QB QB4 QB8 QB9 QB 6 Coclusos I ths paper, a ew mappg scheme, -INode, s troduced to support dyamc updatg of XML documets. I the expermetal study, the query performace ad the effectveess of supportg dyamc updatg XML documets are studed. -INode outperforms or has smlar serto ad query performace most cases comparso wth other methods. Acowledgemet The wor of the authors are supported part by the Cetral Grat of The Hog Kog Polytechcs Uversty, research proect code H-ZJ89. 7 Refereces YoshKawa, M.A. T. (). XRel: a path-based approach to storage ad retreval of XML documets usg

9 relatoal databases. ACM Trasactos o Iteret Techology (TOIT),. (): pages -4. Deutsch, A., Feradez, M., ad Sucu, D. (999). Storg Semstructured Data wth STORED, Proceedgs of the 999 ACM SIGMOD teratoal coferece o Maagemet of Data, pages 43-44, ACM Press. Wag, W.Q., Lee, M.L., Oo, B.C., ad Ta, K.-L. (). XStorM: A Scalable Storage Mappg Scheme for XML Data. World Wde Web,. 4(-): pages -9. Florescu, D. ad Kossma, D. (999). A Performace Evaluato of Alteratve Mappg Schemes for Storg XML Data a Relatoal Database. INRIA. pages 3. Jag, H., Lu, H., Wag, W., ad Yu, J.X. (), Path materalzato revsted: a effcet storage model for XML data. Proceedgs of the thrteeth Australasa coferece o Database techologes. pages 85-94, Australa Computer Socety, Ic. Ng, V., Lau, H.K., ad Chu, S.W (). XNode: Fast Retreval of XML Data from Relatoal Tables. IASTED Iteratoal Coferece Iformato Systems ad Databases (ISDB ), Toyo, Japa. Lau, H.K. ad Ng, V. (3). INODE A Eumerato Scheme for Effcet Storage of XML Data. Cooperatve Iteret Computg. 3, Kluwer Academc Publsher, pages Par, C.-W., M, J.-K., ad Chug, C.-W. (). Structural Fucto Ilg Techque for Structurally Recursve XML Queres. The 8th Iteratoal Coferece o Very Large Data Bases, pages 83-94, Hog Kog, Cha. Kha, D.D., M. Yoshawa, ad S. Uemura (). A Structural Numberg Scheme for XML Data. EDBT Worshops, Lecture Notes Computer Scece 49, Sprger-Verlag Hedelberg, pages 9-8. Chamberl, D., Fahauser, P., Marchor, M., ad Robe, J. (). XML query use cases. Worg Draft December. The Bosa Shaespeare collecto. () Schmdt, A.R., et al. (). The XML Bechmar Proect. Lau, H.K. ad Ng, V. (4), INode*: A Effectve Approach for Storg XML usg Relatoal Database. IJWET Joural Specal Issue o INTERNET AND DATABASE. (To be publshed)

10 Appedx ( ) ) ( c Paret () >,, ) ( 3 a a a path f c c c () ( ) ( ) ( ) ( ) ( ) [ ] ( ) ( ) ( ) ( ) [ ] ( ) ( ) ), ( o d o d o o d d Paretd d o o d d o Paretd d o o d d Paret L (3) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ), ), ( l l l o d o d o d d Acestor o o d d d Acestor d o o d d l l Acestor (4) Table. Database Schema of -INode Usg Two Dmesos Node ID. Table Database Attrbutes Path PathID, Le, PathExp Elemet NodeID, Order, NodeID, Order, DocID, PathID, Ordal, Value, Dm Attrbute NodeID, Order, NodeID, Order, DocID, PathID, Value, Dm Acestor Dfferece, Compoet, Compoet