Conflicts Analysis for Inter-Enterprise Business Process Model

Transcription

1 Conflits Analysis for nter-enterprise Business Proess Moel Wei DNG, Zhong TAN, Jian WANG, Jun ZHU, Haiqi LANG,Lei ZHANG {ingw, tianz, wangwj, zhujun, lianghq, BM China Researh Lab, BM Haohai Builing, 5th Shangi Street, Haiian Distrit Beijing, , China ABSTRACT Abstrat: Business proess (BP) management systems failitate the unerstaning an exeution of business proesses, whih ten to hange frequently ue to both internal an external hange in an enterprise. Therefore, the nees for analysis methos to verify the orretness of business proess moel is beoming more prominent. One key element of suh business proess is its ontrol flow. We show how a flow speifiation may ontain ertain strutural onflits that oul ompromise its orret exeution. n general, ientifiation of suh onflits is a omputationally omplex problem an requires evelopment of effetive algorithms speifi for target system language. We present a verifiation approah an algorithm that employs onition reahable matrix to ientify strutural onflits in inter-enterprise business proess moels. The main ontribution of the paper is a new tehnology for ientifying strutural onflits an satisfying well-efine orretness riteria in inter-enterprise business proess moels. Keywors: Business Proess Moeling, Conflits Detetion, Conflits Analysis, Conitional Reahable Matrix, Business Proess Analysis 1. NTRODUCTON n this information age, e-business is key to business survival. As reporte by AMR Researh n., e-business rastially inreases the nee to effetively manage omplex, ross-enterprise business proesses. e-business Proess Management (ebpm) requires a ombination of proess moeling an analysis, appliation exeution, workflow management, appliation integration, an proess intelligene. Consequently, Business proesses relate to inter-enterprise exhange are beoming inreasingly important. A flow speifiation may ontain ertain strutural onflits that oul ompromise its orret exeution. The researh presente in this paper fouses on inter-enterprise BP verifiation in a omputational effetive way. Lots of work existe in BP moeling an verifiation omain. A verifiation metho use in APM [1] is aapte the algorithms oming from Yang's in PPP [2]. The metho is to onstrut a omplete state transition iagram to simulate all possible exeution paths of the proess an hek whether they are onsistent. This, however, woul fae the ombinatorial explosion problem leaing to poor performane. n [] some verifiation problems are overe an the omplexity of selete orretness problems are ientifie, but no onrete verifiation proeures are available. n [4] an [5] verifiation proeures base on Petri net are propose. The tehnology presente in [5] is evelope for heking the onsisteny of transational workflows inluing temporal onstraints. However, the tehnology is restrite to ayli workflows an only gives the neessary onitions. n [6] a reution tehnology is propose, whih efines a sounness riterion, an the lass of workflow proesses onsiere is in essene ayli free-hoie Petri nets. This paper iffers from the above approahes by fousing on inter-enterprise BP. A few papers expliitly fous on the problem of verifying the orretness of interorganizational workflows [7, 8]. n [7] the interation between omains is speifie in terms of message sequene harts an the atual overall workflow is heke with respet to these message sequene harts. A similar, but more formal an omplete approah is presente by Kinler, Martens, an Reisig in [8]. The authors give loal riteria, using the onept of senarios (similar to runs or basi message sequene harts), to ensure the absene of ertain anomalies on the global level. Rest of the paper is organize as follows. n setion 2, we efine an explain a generi business proess moeling language to buil proess moels. n setion, we analyze the strutural onflits of inter-enterprise BP moel an give a orretness riterion. On the basis of strutural onflits analysis, a verifiation approah that employs onition reahable matrix is presente in setion 4. Setion 5 onlues the paper. 2. NTER-ENTERPRSE BUSNESS PROCESS MODELNG Fig.1 shows our moeling objets whih inlues: noes, onnetors an flows. Noes Ativity A Start Point En Point Connetors Merge (OR Join) Choie (OR Split) Synhronizer (An Join) Fork (An Split) Flows Control Flow nformationl Flow Fig.1 nter-enterprise BP moeling objets 24 SYSTEMCS, CYBERNETCS AND NFORMATCS VOLUME 1 - NUMBER

2 There are mainly four types of noes: Ativity is a work to be one to ahieve ertain objetives. A (nformation Artifat) orrespons to the exhange of message between multiple BPs. The moel shoul have one Start Point an at least one En Point. There are four types of BP logial onnetors: Choie (OR-Split), Merge (OR-Join), Fork (AND-Split) an Synhronizer (AND-Join). An-split is use to represent onurrent paths within a BP. An-join is applie to synhronize suh onurrent paths. Or-split is use to moel mutually exlusive alternative. Or-join is applie to join mutually exlusive alternative paths into one path. There are two types of flows: ontrol flow an information flow. Control flow links two noes in the intra-enterprise BP moel. nformation flow links two As or A-with-ativity to represent information sening/reeiving ation.. STRUCTURAL CONFLCT DEFNTON N NTER-ENTERPRSE BP Some BP moeling assumptions are given firstly in this setion. Following the general struture valiity efinition, the onrete strutural onflit efinitions in both intra an inter BPs are given separately, as the founation for the new onflits etetion approah introue in setion 4. Assumption A proess moel base on above moeling objets onstruts a Direte Ayli Graph (DAG), whih onforms to the following assumption: 1. t oesn't have any loops whih are eges from a vertex to itself; 2. t oesn't have any multiple eges between pairs of noes;. t oesn't have any iteration struture; Terms an Definitions Before ientifying strutural onflits an presenting the orretness riteria for inter-enterprise BP moel, some efinitions nee to be introue firstly. (See Definition 1-4) Definition 1: An instane subgraph represents a subset of business proess moel that may be exeute for a partiular instane of a business proess. An instane subgraph an be generate by visiting its noes on the semanti basis of unerlying moeling strutures. The or-split, whih is exlusive an omplete, is the only struture in a business proess moel that introues more than one possible instane subgraphs. At runtime, the BP moel selets one of the alternative exeution paths for a given instane of the business proess by ativating one of the outgoing flows originating from the or-split onition objet. Figure 2 shows a business proess graph an its two instane subgraphs. a ) A proess moe b ) nstane for hoie 1 ) nstane for hoie 2 Fig.2 Example intra-bp Moel with flow ealok strutural onflits Definition 2: Choie Path: A hoie path of noe n is a sequene of hoie branh <1,2...k> from start point to noe n. Choie path is a useful efinition that represents a noe in some instane subgraph of the BP moel. A noe may have several ifferent hoie paths. ChoieSignpost is a hoie set whih represents the entire hoie path by set. f two noes in intra-enterprise BP moel have the same hoie path, then the two noes are always in the same instane subgraph. Ativities an serve as a goo example in Figure 2. Definition :An intra-enterprise BP moel (ntra-bpm) is a tuple: ntra-bpm=(n, F), where: N is a finite set of noes (without A). F `(N%N) is a finite set of ontrol flows representing irete eges between two noes. Definition 4 :An inter-enterprise BP moel (nter-bpm) is a tuple: nter-bpm=(n1,,n2,f2,m,t), where: N1 is a finite set of partner1's noes (without A). `(N1%N1) is a finite set of partner1's ontrol flows. N2 is a finite set of partner2's noes (without A). F2`(N2%N2) is a finite set of partner2's ontrol flows. M is a finite set of A pairs. T is a finite set of information flows representing irete eges between two noes. A formal notation of BP moel use in the onflits etetion is given as follows. For eah flow f F: start[f] = n represents start noe n of f. en[f] = n represents en noe n of f. For eah noe an onnetor n N: type[n] {Start Point, En Point, Merge, Synhronizer, Fork, Choie, Ativity} represents type of n. out[n] : number of outgoing flows from n. in[n] : number of inoming flows to n. Choiesignpost[n,i] where n N an 1ñ iñ in[n],represents hoie set of noe n entry i from start point to noe n. f the noe has only one entry(for example :ativity), parameter i an be omitte. For eah A pair m M has only one sener an one reeiver: SYSTEMCS, CYBERNETCS AND NFORMATCS VOLUME 1 - NUMBER 25

3 Reeiver[m]= n={ m : m M, n: n N14N2, type(n)={ativity} an t T,where start[t]=m an en[t] = n }, n is the reeiver ativity of the A pair m. Sener[m]= n={ m : m M, n: n N14N2, type(n)={ativity} an t T, where start[t] = n an en[t] = m }, n is the sener ativity of the A pair m. nter-enterprise BP Struture Conflit Definition Definition 5: A business proess moel is sai to be strutural orret if an only if it is: 1. Syntatial orret: Eah objet satisfies objet types an the number of inoming an outgoing flows onnete to it. 2. Reahability an termination error free: Eah noe is reahable from the Start Point an the En Point an be reahe from this noe. Before the verifiation for BP strutural onflits, basi syntax heking is performe to ensure that the moel onforms to the moeling language syntax an that all neessary assumptions of its omponents have been efine. t is important to point out that strutural onflits are not the only types of errors possible in business proess moels. However, they o represent the primary soure of errors in flow speifiations an an be ientifie inepenently. nter-enterprise BP strutural onflits are separate into two ategories: intra-bp an inter-bp onflits. ntra-bp moel orret riterion guarantees proper termination of the moel for all instane subgraph. nter-bp moel orret riterion guarantees proper interation of multiple partners for all instane subgraph. Definition 6 :Corret intra-enterprise BP moel: For any instane subgraph, the proeure will terminate eventually at en point. The or-join an an-join are the only two struture in a business proess moel that may ause the improper flow termination till en point. With this unerstaning, two strutural onflits in intra-enterprise BP moel are ientifie: flow ealok an lak of exlusion. Flow ealok - Joining exlusive hoie with a synhronizer results into a flow ealok onflit. A flow ealok at a synhronizer struture bloks the ontinuation of a business proess path sine one or more the inoming transitions of the synhronizer are not triggere. Figure 2 shows an instane subgraph with flow ealok strutural onflit. n figure 2 ), the proess instane will have a ealok at synhronizer if it selets hoie. Aoringly, this instane woul not terminate properly as an not be exeute. Lak of exlusion - Joining two or more onurrent paths with a merge struture introue lak of exlusion onflit. A lak of exlusion at a merge struture auses unintentional multiple ativation of noes that follow the merge struture. Figure shows an instane subgraph with the lak of exlusion strutural onflit. n figure ), the proess instane will have a lak of exlusion if it selets hoie, sine two parallel ativities an will multiply ativate the noes that follow the merger noe, then the instane woul not terminate properly. a ) A p roess moe b ) nstane for hoie 1 ) nstane for hoie 2 Fig. Example intra-bp Moel with exlusive join strutural onflits t an be ientifie that, the orretness riteria for intra-enterprise BP moel is that the moel is free of flow ealok an lak of exlusion strutural onflits. A BP moel is free of flow ealok strutural onflits if it oes not generate an instane subgraph that ontains only a proper subset of the inoming noes of an an-join noe, i.e. for any synhronizer in the moel, the ChoieSignposts of the all synhronizer entry are equal. A BP moel is free of lak of exlusion strutural onflits if it oes not generate an instane subgraph that ontains more than one inoming noes of an or-join noe. i.e. for any merge in the moel, the any two ChoieSignposts of the all merge entry have no intersetion. Definition 7 :well mapping inter-enterprise BP moel: for any instane subgraph in inter-enterprise BP moel, all A in it are well mapping. Usually, an inter-bp moel has no angling A, whih represents there is no sener or reeiver for the A, but it an not ensure that the inter-bp moel is well mapping. For example, a pair A links two ativities. f the two ativities' ChoieSignposts (hoie path) are not equal, then it means there some two instane subgraphs that the ativities existe are not mathe. So well mapping inter-enterprise BP moel not only has no angling A, but also eah pair of instane subgraph has no angling A. An inter-bp moel is not well mapping just beause the ativities onnete with A pair have ifferent hoie path (ChoieSignpost). A orresponing strutural onflit in inter-bp moel is ientifie as follows: Different hoie path strutural onflits - Two ativities onnete with A pair have ifferent ChoieSignpost. A Different hoie path strutural onflit results into some instane subgraph has angling A. Figure 4 shows an inter-bp moel with ifferent hoie path strutural onflit. Partner A selets hoie uring the runtime, then partner A an only proue 1 an 2 is angling Partner1 Partner2 Fig.4 Example inter-bp Moel with hoie mapping strutural onflits SYSTEMCS, CYBERNETCS AND NFORMATCS VOLUME 1 - NUMBER

4 Definition 8 :well orere inter-enterprise BP moel: n a well mapping inter-enterprise BP moel, the partial orer of A pairs enable both sie proeure terminate eventually at en point for any instane. At runtime, the BP moel of eah partner exeutes a sequene of efine ativities epening on the path hosen. Some ativities may proue or onsume A. f an ativity nees onsuming A, the ativity an be exeute only when the A is available. Otherwise the ativity woul never be ativate. Corresponing strutural onflits are ientifie as follows. A ealok - nonsistent sequene of A proution/onsumption results into an A ealok. An A ealok between partners bloks the ontinuation of a business proess path of both sie sine two ativities nee A an the A is not available. Figure 5 shows an inter-bp moel with A ealok strutural onflit. At runtime, ativity 1 in partner A nee to onsume 1 an then ativate 2 to proue 2. However, ativity 1 in partner B nee to onsume 1 an then trigger 2 to sen 2. So the inter-bp moel woul ealok The ommon point in both ases of onflits etetion is to examine all possible instane subgraphs of a BP moel. The or-split is the only struture in a business proess moel that introues more than one possible instane subgraphs. The number of possible instane subgraphs oul grow exponentially as the number of or-split an or-join struture inreases in a BP speifiation. Therefore, a brute fore metho to generate all possible instane subgraphs of a BP moel to ensure orretness is not omputationally effetive. 4. CONFLCTS DETECTON ALGORTHM n this setion, both effetive intra/inter BP onflits etetion algorithms are introue, given the innovative efinition of onition reahable matrix as basis. Conition Ajaeny Matrix Suppose that G=(N,F) is an intra-bp moel where N =n. For simple, here we suppose type[n]={ativity}. The onition ajaeny matrix A(G), with respet to the noes, is the n% n matrix with as its (i,j)th entry when noe ni an nj are iretly ajaent, an as its (i,j)th entry when they are not ajaent, an hoie set, for example {}, as its (i,j)th entry when they are ajaent by hoie. 2 2 Fig. 5 Example inter-bp Moel with A ealok strutural onflits Lak of synhronization - nonsequent sequene of A proution/onsumption introue a lak of synhronization. Stritly speaking, lak of synhronization will not result into ealok of the inter-bp moel, but it is not eonomial in the real life. Figure 6 shows an inter-bp moel with two kins of lak of synhronization strutural onflit Fig. 6 Example inter-bp Moel with Lak of synhronization strutural onflits Given the basi orretness efinition above, the omplete orretness riterion for inter-bp moel are introue in Definition 9. Definition 9 :A orret inter-enterprise BP moel satisfies the following requirements: (1) Eah intra-enterprise BP moel is orret; (2) nter-enterprise BP moel is well mapping; () nter-enterprise BP moel is well orere; Conition Reahable Matrix Aoring to onition ajaeny matrix of an intra-bp moel, noe onition reahability an be alulate. The onition reahable matrix represents the mutually reahable properties of any two noes in the moel. ts generation proeure is esribe as follows. Proeure: Conition reahable matrix generation (A(G): n% n onition matrix) M:= A(G); For i:=1 to n Begin for j:=1 to n Begin f M[j,i]! then For k:=1 to n Begin En En En A[j,k]:=A[j,k] 4{A[i,k] [Mj,i]} Conflits Detetion Algorithm The intra-bp onflits etetion proeure is esribe as follows. Proeure: ntra-bp moel strutural onflits etetion For any noe n, n N f type(n)={synhronizer} an Choiesignpost[n,1]= Choiesignpost[n,2]=...= Choiesignpost[n,k] (k is the number of entry of noe n ) The BP moel ontains no flow ealok onflits Else Report noe n with flow ealok SYSTEMCS, CYBERNETCS AND NFORMATCS VOLUME 1 - NUMBER 27

5 f type(n)={merge} an Choiesignpost[n,i]!! Choiesignpost[n,j], i j (i an j are the any two entry of noe n ) Report noe n with exlusive join onflits nter-bp onflits etetion proeure is esribe as follows. Proeure: nter-bp moel strutural onflits etetion For any A pair m, m M f Choiesignpost[Reeiver(m)]! Choiesignpost[Sener(m)] Report noes Reeiver(m) an Sener(m) with hoie mapping strutural onflits For any two A pair mi an mj, mim,mj M Swith Case 1 (Reeiver(mi) N1 an Reeiver(mj) N1) or (Reeiver(mi) N2 an Reeiver (mj) N2) f (Reeiver(mi) Reeiver(mj) an Sener(mj) Sener(mi)) or Reeiver(mj) Reeiver(mi) an Sener(mi) Sener(mj)) Report the four ativities that link A pair mi an mj ontains lak of synhronization onflits Case 2 (Reeiver(mi) N1 an Reeiver(mj) N2) or (Reeiver(mi) N2 an Reeiver(mj) N1) f Reeiver(mi) Sener(mj) an Reeiver(mj) sener(mi)) Report the four ativities that link A pair mi an mj ontains A ealok onflits f Sener(mi) Reeiver(mj) an Sener(mj) Reeiver(mi)) Report the four ativities that link A pair mi an mj ontains lak of synhronization onflits Here is a reahable symbol. For example, for noe n1 an n2, n1 n2 represents n2 is reahable from n1. 5. CASE STUDY An inter-enterprise BP moel is shown in Figure 7. Corresponing onition ajaeny/reahable matries an be seen in Table 1~4. B1 B B4 B5 Table. 1 Conition ajaeny matrix of partner A Table. 2 Conition reahable matrix of partner A 4() Table. Conition reahable matrix of partner B B1 4() B B4 B5 4() 4() B1 B4 M F2 S2 M4 B5 M2 EP EP Partner A Partner B Fig. 7 An inter-enterprise business proess moel B Let's use the synhronizer in partner A sie, an Merge M4 in partner B sie to illustrate the onflits etetion proeure introue in the paper. 4 ChoieSignpost[,1]=ChoieSignpost[]= ( ), ChoieSignpost[,2]=ChoieSignpost[]=,! As ChoieSignpost[,1] ChoieSignpost[,2], there is a flow ealok reporte at. Similarly, ChoieSignpost[M4,1]= ( ), 4 4 ChoieSignpost[M4,2]=, ChoieSignpost[M4,1] ChoieSignpost[M4,2]=( ) [ ( )]=( ) ( )= Hene, M4 is free of lak of exlusion strutural onflit. 28 SYSTEMCS, CYBERNETCS AND NFORMATCS VOLUME 1 - NUMBER

6 Different hoie path strutural onflit of the given inter BP moel an be analyze through omparing the partners' onition reahable matries, as shown in Table 4. Table. 4 Different hoie path strutural onflits analysis B1 Conflit No No 4() Yes 4 ( ) B B4 B5 No Yes Yes 4() 4() Let us analyze A ealok in this ase. For two pairs of A: m2= an m4=, the ativity of Reeiver[m2] is, whih belongs to partner A, an the ativity of Reeiver[m4] is B4, whih belongs to partner B. From the onition reahable matrix of the two partners(as shown in table 2 an table.), we an fin: an B4. At runtime, ativity in partner A nee to onsume an then ativate to proue. However, ativity B4 in partner B nee to onsume an then trigger to sen. So the inter-bp moel woul ealok at ativities: an B4. Similarly, we an fin all the A ealok in the inter-bp moel. 6. CONCLUSONS No [4] W.M.P. van er Aalst, Verifiation of Workflow Nets, n P. Az ema an G. Balbo, eitors, Appliation an Theory of Petri Nets 1997, volume 1248 of Leture Notes in Computer Siene, pages Springer-Verlag, Berlin, [5] N.R. Aam, V. Atluri, anw. Huang, Moeling an Analysis ofworkflows using Petri Nets, Journal of ntelligent nformation Systems, 10(2): [6] W. Saiq an M.E. Orlowska, Applying Graph Reution tehnology for entifying Strutural Conflits in Proess Moels, n Proeeings of the 11th nternational Conferene on Avane nformation Systems Engineering (CAiSE' 99, volume 1626 of Leture Notes in Computer Siene, pages Springer-Verlag, Berlin, [7] W.M.P. van er Aalst, nterorganizational Workflows: An Approah base on Message Sequene Charts an Petri Nets, Systems Analysis - Moelling - Simulation, 4(): [8] E. Kinler, A. Martens, an W. Reisig, nter-operability of Workflow Appliations: Loal Criteria for Global Sounness, n W.M.P. van er Aalst, J. Desel, an A. Oberweis, eitors, Business Proess Management: Moels, tehnologys, an Empirial Stuies, volume 1806 of Leture Notes in Computer Siene, pages Springer-Verlag, Berlin, n this paper we report our approah of using onition reahable matrix tehnology for eteting strutural onflits in inter-enterprise business proess moels. A graphi proess moel representation is provie as basis for our verifiation approah an orresponing algorithms. Corretness riteria of inter-enterprise BP moel an major several types of strutural onflits are ientifie. An effetive algorithm base on onition reahable matrix is then illustrate for both intra an inter-bp struture onflit verifiation. The approah is intuitive an natural. Strutural onflits an be ientifie easily an aurately with the generating of onition reahable matrix. Whereas, as ifferent parties may have ifferent voabulary/symbol to represent the same onition branh expressions, the algorithm we reporte in this paper still nee to rely on user partiipation to avoi reporting ontology misunerstaning as onflits. Although the approah presente in this paper eals with business proess moel that an be represente by a irete ayli graph (DAG), our further stuy fins the metho an be applie to BP moel with yles an iteration struture. 7. REFERENCES [1] S.Carlsen,Coneptual Moeling an Composition of Flexible Workflow Moels, Ph.D.Thesis, Department of Computer an nformation Siene, Norwegian University of Siene an Tehnology,1997. [2] Mingwei Yang, COMS-A Coneptual Moel for nformation Systems, Ph.D. Thesis, Norwegian nstitute of Tehnology,199. [] A.H.M. ter Hofstee, M.E. Orlowska, an J. Rajapakse, Verifiation Problems in Coneptual Workflow Speifiations, Data an Knowlege Engineering, 24():29-256, SYSTEMCS, CYBERNETCS AND NFORMATCS VOLUME 1 - NUMBER 29