999 Computer System Network. (12) Patent Application Publication (10) Pub. No.: US 2006/ A1. (19) United States

Transcription

1 (19) United State US 2006O A1 (12) Patent Application Publication (10) Pub. No.: Mueller et al. (43) Pub. Date: Jun. 15, 2006 (54) METHOD AND COMPUTER SYSTEM FOR QUEUE PROCESSING (76) Inventor: Wolfgang G. Mueller, Wieloch (DE); Hartmut Willy, Wieloch (DE) Correpondence Addre: FISH & RICHARDSON, P.C. PO BOX 1022 MINNEAPOLIS, MN (US) (21) Appl. No.: 11/272,047 (22) Filed: Nov. 10, 2005 (30) Foreign Application Priority Data Nov. 12, 2004 (EP)... O Publication Claification (51) Int. Cl. G06F 15/177 ( ) (52) U.S. Cl /220 (57) ABSTRACT The cheduler receive a firt meage from one of the plurality of computer ytem and regiter the firt meage in a firt queue. Then, the cheduler receive a econd meage from one of the plurality of computer ytem. The econd meage ha a logical dependency on the firt meage. The econd meage i regitered in a econd queue and in the firt queue, wherein the queue entry of the econd meage in the firt queue occur after the queue entry of the firt meage in the firt queue. The cheduler identifie the logical dependency of the econd meage on the firt meage by the order of the correponding queue entrie in the firt queue and finally releae the firt meage for proceing before releaing the econd meage accord ing to the logical dependency Computer Sytem Network 900

2 Patent Application Publication Jun. 15, 2006 Sheet 1 of 14 US 2006/ A Computer Sytem Network FIG

3 Patent Application Publication Jun. 15, 2006 Sheet 2 of 14

4 Patent Application Publication Jun. 15, 2006 Sheet 3 of 14 S

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10 Patent Application Publication Jun. 15, 2006 Sheet 9 of 14 Ja?mp3?9S /10? 20000

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12 Patent Application Publication Jun. 15, 2006 Sheet 11 of 14 97ffa6eauu0Z y 1947

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14 Patent Application Publication Jun. 15, 2006 Sheet 13 of 14 36eau! 999

15 Patent Application Publication Jun. 15, 2006 Sheet 14 of

16 US 2006/ A1 Jun. 15, 2006 METHOD AND COMPUTER SYSTEM FOR QUEUE PROCESSING CROSS REFERENCE TO RELATED APPLICATION Thi application claim priority to European Patent Application No , filed Nov. 12, 2004, the con tent of which are hereby incorporated by reference. TECHNICAL FIELD 0002 The preent invention generally relate to elec tronic data proceing, and more particularly, relate to method, computer program product and ytem for queue proceing. BACKGROUND 0003 Scheduler being computer program that coordi nate the ue of hared reource are known in the art. Typically, Scheduler put job or meage to be cheduled for execution at a later point in time into a queue. A queue i a data tructure in which element are removed in the ame order they were entered. Thi i often alo referred to a FIFO (firt in, firt out) For example, SAP AG ue a queue cheduler a a component of it integration technology for proceing meage queue in it Supply Chain Management product. The queue cheduler i configured to upport the replication of meage on a firt ytem into a econd ytem by making Sure that the order of meage i repected when proceing the meage in the econd ytem The queue cheduler can handle multiple queue to enable parallel proceing of meage. Parallel proceing become important when high quantitie of meage need to be proceed Meage can have logical dependencie. For example, a meage for creating a cutomer order can trigger a firt queue entry for the order and a further queue entry for an aociated material that i ued by the order. A econd meage for a econd cutomer order may trigger an entry for the econd order in a further queue. In cae the econd order ue the ame material a the firt order a further queue entry for the ame material i generated, which implie a logical dependency between the firt and econd meage The queue cheduler read queue information from a databae, where all queue information i tored when a meage trigger a queue entry. By uing Such a pull baed approach, the queue Scheduler only know the queue tatu at the point in time when the lat databae read wa performed. The latet meage often are not known by the cheduler although being queued already in the databae. Further, the queue Scheduler can only proce thoe me age that can be proceed without dependency knowledge (typically the oldet queue entrie). Thi procedure make the cheduler low epecially in the cae of many parallel queue. A dependency can block the proceing of meage even when they are queued in different queue. Thi may caue the queue Scheduler to dicard the blocked meage to free memory and reread thee meage at a later point in time. A a conequence, it i difficult to ue the cheduler in cenario that require real-time queue replication between different ytem. SUMMARY In one apect of the invention the problem of real-time meage ynchronization acro a plurality of computer ytem i olved by the feature of the indepen dent claim A cheduler computer program product i config ured to proce meage of at leat one of a plurality of computer ytem in a further computer ytem of the plurality of computer ytem. The cheduler receive a firt meage from one of the plurality of computer ytem and regiter the firt meage in a firt queue. Then, the ched uler receive a econd meage from one of the plurality of computer ytem. The econd meage ha a logical depen dency on the firt meage. The econd meage i regitered in a econd queue and in the firt queue, wherein the queue entry of the econd meage in the firt queue occur after the queue entry of the firt meage in the firt queue. The cheduler identifie the logical dependency of the econd meage on the firt meage by the order of the correpond ing queue entrie in the firt queue and finally releae the firt meage for proceing before releaing the econd meage according to the logical dependency The cheduler can guarantee that the proceing of meage that originate in a plurality of computer ytem i performed by alway repecting logical dependencie between the variou meage. Thi guarantee data coni tency acro multiple computer ytem The apect of the invention will be realized and attained by mean of the element and combination par ticularly pointed out in the appended claim. It i to be undertood that both the foregoing general decription and the following detailed decription are exemplary and explanatory only and are not retrictive of the invention a decribed. DESCRIPTION OF DRAWINGS 0012 FIG. 1 i a implified block diagram of a computer ytem network for queue proceing: 0013) FIG. 2 how a cheduler queuing a firt meage; 0014) FIG. 3 how the cheduler queuing a econd meage; FIGS. 4 and 5 how the cheduler reolving a meage dependency; 0016 FIGS. 6 to 10 how a further example where the cheduler reolve dependencie for four meage; 0017 FIG. 11 illutrate a topological orting algorithm for meage dependency reolution; 0018 FIG. 12 how an alternative embodiment of the invention including periting mean for meage; FIGS. 13A, 13B how a implified flow chart of a firt method according to one embodiment of the invention including a recovery mechanim of the cheduler, 0020 FIGS. 14A, 14B how a implified flow chart of a econd method according to an alternative embodiment of the invention including a recovery mechanim of the ched uler.

17 US 2006/ A1 Jun. 15, Like reference ymbol in the variou drawing indicate like element. DETAILED DESCRIPTION 0022 FIG. 1 i a implified block diagram of a computer ytem network 999 for queue proceing. The computer ytem network 999 include a firt, econd and third computer ytem 901, 902, 903 for running application ytem AS1, AS2 and AS3, repectively. In the example, the firt application ytem AS1 ha at leat a firt applica tion 201, the econd application ytem AS2 ha at leat a econd application 202 and the third application ytem AS3 ha at leat a third application ASn. Any number of computer ytem may be included in the network 999. Each appli cation ytem can have a deliberate number of application The computer ytem network 999 further include a further computer ytem 900 for running a further appli cation ytem AS0. A cheduler 100 computer program i tored in a memory 910 of the further computer ytem 900. The cheduler 100 ha intruction that can be executed by one or more proceor of the further computer ytem 900. The cheduler can queue meage received from the other computer ytem in the computer ytem network 999 in Such a way that all meage are proceed by the further application ytem ASO alway in the correct order even when logical dependencie exit between variou meage The queue of the cheduler 100 can be real time replication of meage queue generated in the variou application ytem It i alo poible that one computer ytem run multiple application ytem. In thi cae the meage may alo originate inide the further computer ytem The computer ytem can communicate with each other over a network 990. In the cae of multiple applica tion ytem running within a ingle computer ytem the communication via network 990 can be replaced by a hared memory communication within the computer ytem. In oftware, the term hared memory refer to memory that i acceible by more than one proce, where a proce i a running intance of a program. In thi context, hared memory i ued to facilitate interproce communication FIGS. 2 to 5 how an example where the cheduler 100 handle two meage having a logical dependency. A fundamental difference to the prior art cheduler i that the cheduler 100 doe not rely on a pull mechanim. Intead of actively pulling queue information from a databae, the cheduler get notified by the application ytem by end ing meage directly to the cheduler 100. Thi way the cheduler 100 can trigger the execution of meage in the receiving application ytem hortly after the generation of the meage in the ending application ytem. That i, only a hort time elape between meage generation and execu tion o that the meage replication doe not become a bottleneck of the computer ytem with repect to meage proceing In FIG. 2, the cheduler 100 receive a firt me age 301 from an application 201 that i run on the firt computer ytem 901. The firt meage can alo originate in the ytem that i running the cheduler 100. However in the following example it i aumed that the meage originate in another ytem. For example, the meage correpond to a tranaction for creating a cutomer order in the firt computer ytem 901. The executed tranaction can thu be regarded a the meage creator. For conitency reaon, the cutomer order ha alo to be created in the further computer ytem 900 running the cheduler Then, the cheduler regiter the firt meage 301 in a firt queue Q1. In the example, thi could be a queue for queuing cutomer order. Each regitration entry of a pe cific meage in a queue i illutrated by an X in a column for the repective meage. The column i illutrated by dotted line and ha a header with the meage name For example, the queue can be tored in a memory portion of the further computer ytem memory In cae the firt meage 301 i queued in the firt computer ytem 901 the regitration of the firt meage 301 in the firt queue Q1 of the cheduler 100 correpond to a replication of the correponding queue in the firt computer ytem 901. In other word, in one implementation the firt computer ytem 901 may run it own local ched uler, which queue the meage originating in the firt computer ytem. The local cheduler can be reponible for controlling the order in which meage are ent to the cheduler 100. In thi implementation the cheduler 100 can be conidered a a central cheduler, which receive and queue meage from application to replicate the queue from at leat one correponding local cheduler. 0032). In FIG. 3, the cheduler 100 receive a econd meage 302 from the application 201 that i executed on the firt computer ytem 901. In general, the econd meage can originate alo from another application run by the ame or another computer ytem. For example, the meage correpond to a tranaction for delivering the cutomer order created by the firt meage 301. The econd meage 302 ha a logical dependency on the firt meage 301. A logical dependency between meage can originate in that both meage affect the ame object (e.g., cutomer order). In general, the econd meage can have dependent object that are affected by executing the econd meage. For example, when the delivery of the cutomer order i executed, the tatu of the cutomer order i modified (e.g., tatu=delivered). That i, the econd meage 302 affect the object (cutomer order) that alo i ubject to the firt meage 301. It i clear that the tatu of the cutomer order cannot be modified before the cutomer order ha been created. Therefore, a logical dependency between the two meage exit implying that the firt meage 301 ha to executed before the econd meage 302 in any cae The cheduler 100 then regiter the econd me age 302 in a econd queue Q2 and in the firt queue Q1, wherein the queue entry of the econd meage 302 in the firt queue Q1 occur after the queue entry of the firt meage 301 in the firt queue Q1. In general, the econd meage i regitered on all queue of the cheduler 100 that relate to dependent object of the econd meage. In other word, the econd meage i regitered on all queue that relate to an object affected (e.g., modified) through the meage. In real application ytem, a meage can affect many object leading to broad dependencie The econd queue Q2 can be a queue for queuing deliverie wherea the regitration of the econd meage 302 in the firt queue 301 indicate the logical dependency on the firt meage 301 that ha been regitered before in the ame queue.

18 US 2006/ A1 Jun. 15, ) The cheduler 100 can identify the logical depen dency of the econd meage 302 on the firt meage 301 by the order of the correponding queue entrie 301-1, in the firt queue Q1. In cae of an application ytem that ue a plurality of proceor for achieving parallelization to handle high meage Volume hundred of queue and broad dependencie may exit. The example hown in FIGS. 6 to 11 dicloe how to identify logical dependencie in Such an environment. 0036) Once the cheduler 100 ha recognized the depen dency, the firt meage 301 can immediately be proceed becaue it i not dependent on any previou meage. Therefore, the cheduler 100 releae the firt meage 301 for proceing and delete the queue entrie related to the firt meage 301 a illutrated by FIG After the deletion, the remaining queue entrie of the econd meage 302 in the firt and econd queue Q1, Q2 have no dependency any more on a previou meage Therefore, a hown in FIG. 5, the econd meage 302 can now be proceed. The cheduler 100 releae the econd meage for proceing and delete the queue entrie related to the econd meage 302 after the econd meage 302 wa uccefully executed The above decribed procedure enure that the firt meage 301 i proceed before the econd meage 302 according to the logical dependency and data coni tency in the further computer ytem 900 i guaranteed FIGS illutrate a further example with mul tiple logically dependent and independent meage. The example i baed on meage originating in a firt appli cation ytem. However, the meage proceed by Sched uler 100 can originate in multiple application ytem. Alo the decribed logical dependencie between meage can exit between meage originating from different applica tion ytem In FIG. 6, a firt tranaction Cr/CO1 i executed by the firt application 201 on the firt computer ytem 901. For example, the tranaction create a firt cutomer order CO1. Thi cutomer order can be put into a correponding queue of a local cheduler (not hown) of the firt computer ytem In cae the queue entry need to be replicated to the further computer ytem 900, a correponding firt meage 310 i ent to the cheduler 100 of the further computer ytem 900, for example, by the local cheduler of the firt computer ytem 901. The local cheduler of the firt computer ytem 901 can be implemented with the ame functionality a the central cheduler 100. Thi correpond to a pecial implementation where the ytem generating the meage i alo the ytem running the cheduler (e.g., further computer ytem 900) For example, the firt computer ytem 901 may run a firt application ytem AS1 (e.g., an Enterprie Reource Planning ytem or a Cutomer Relationhip Man agement ytem) and, for example, the further computer ytem 900 may run a planning and imulation ytem or any other application ytem that ha to take into account all cutomer order and related data from other application ytem for planning purpoe. 0044) In the example of FIG. 6, the firt meage regi ter itelf in three queue (CO1, M1, M2) The regitration of the firt meage 310 in queue CO1 implie that the cutomer order CO1 ha to be created in the further computer ytem 900. The regitration in queue M1 and M2 implie that for the fulfillment of cutomer order CO1 the material M1 and M2 are needed and, for example, correponding material movement have to be taken into account by the planning and imulation ytem. 0046) When the cheduler 100 receive the firt meage 310, the cheduler 100 can provide a unique timetamp to the meage 310 according to which the meage i regi tered in the queue CO1, M1 and M2. The timetamp can be implemented by a counter or any other mean that how a trictly monotonic behavior over time and allow to aign a unique value to each received meage In FIG. 7, a econd tranaction Cr/CO2 i executed by the firt application 201 on the firt computer ytem 901. For example, the tranaction create a econd cutomer order CO A correponding econd meage 320 i ent to the further computer ytem 900, where it i received by a Scheduler 100. When the Scheduler 100 receive the econd meage 320, the cheduler 100 provide a unique time tamp to the econd meage The econd meage 320 regiter, itelf in corre ponding queue of the cheduler 100 according to the timetamp. That i, in cae the econd meage require regitration in the ame queue a the firt meage, the timetamp clearly indicate, that the queue entry of the econd meage occur after the queue entry of the firt meage In the example of FIG. 7, the regitration of the econd meage 320 occur for the queue CO2, M2 and M3. The regitration of the econd meage 320 in queue CO2 implie that the cutomer order CO2 ha to be created in the further computer ytem 900. In general, the creation of CO1 and CO2 could occur in parallel becaue the correponding meage are regitered in different cutomer order queue (e.g., queue CO1, CO2). However, the reg itration of the econd meage 320 in queue M2 and M3 implie that for the fulfillment of cutomer order CO2 the material M2 and M3 are needed and, for example, corre ponding material movement have to be taken into account by the planning and imulation ytem. Becaue CO1 alo ue material M2, there i a logical dependency of the econd meage 320 on the firt meage 310. The cutomer order CO2 related to the econd meage 320 may not be created before the cutomer order CO1 related to the firt meage 310 becaue both cutomer order ue the ame material M2. For example, if the cutomer order CO1 ue all of the available material M2, then cutomer order CO2 cannot be cheduled for immediate production becaue the required material M2 would not be available. 0051) If the cheduler 100 would not repect the logical dependency between the meage by releaing the creation of the econd order CO2 in parallel with the creation of the firt order CO1, the ytem could end up in an undetermined State.

19 US 2006/ A1 Jun. 15, In FIG. 8, a third tranaction Ch/CO1 i executed by the firt application 201 on the firt computer ytem 901. For example, the tranaction change the firt cutomer order CO1 by changing the number of ordered item A correponding third meage 330 i ent to the further computer ytem 900. When the cheduler 100 receive the third meage 330, the cheduler 100 provide a unique timetamp to the third meage The third meage 330 regiter itelf in corre ponding queue of the cheduler 100 according to the timetamp after the econd meage In the example of FIG. 8, the regitration of the third meage 320 occur for the queue CO1, M1 and M2. The regitration of the econd meage 330 in queue CO1 implie a logical dependency on the firt meage 310 expreing that the cutomer order CO1 hat firt to be created before it can be changed In FIG.9, a fourth tranaction Cr/CO3 i executed by the firt application 201 on the firt computer ytem 901. For example, the tranaction create a third cutomer order CO A correponding fourth meage 340 i ent to the further computer ytem 900. When the cheduler 100 receive the forth meage 340, the cheduler 100 provide a unique timetamp to the fourth meage The fourth meage 340 regiter itelf in corre ponding queue of the cheduler 100 according to the timetamp after the third meage In the example of FIG. 9, the regitration of the fourth meage 340 occur for the queue CO3 and M4. There are no queue entrie from previou meage in thee queue. That, i the fourth meage 340 ha no logical dependency on any of the previou meage FIG. 10 how the cheduler 100 after having reolved a logical dependency in the queue CO1, CO2, CO3, M1, M2, M3 and M In the example of FIG. 10 the cheduler ha applied a logical dependency reolution algorithm to the queue in the cheduler a of FIG. 9. The cheduler ha identified all meage without logical dependencie. Thee meage 310,340 can, therefore, be proceed immediately. For example, the cheduler can put the identified indepen dent meage into a correponding pool of independent meage 110. Potentially, all meage in thi pool 110 can be proceed in parallel. Once the independent meage 310,340 are lited in the pool 110, the correponding queue entrie in the cheduler 100 are removed. 0062) The pool 110 can be implemented in the memory 910 of the further computer ytem 900 by any data tructure Suitable to tore a plurality of meage For example, the cheduler can ue a topological orting algorithm for reolving the logical dependencie in the variou queue. A topological orting algorithm i explained in detail in FIG FIG. 11 how the reult of the logical dependency reolution by uing a topological orting algorithm A topological ort i a partial orting of element. The reult lit i not necearily fully orted. However, certain rule between the element of the lit (e.g., logical dependencie) have to be repected by the orting algorithm The logical dependencie expreed in the order of queue entrie define limiting rule for the algorithm. That i, if two meage are regitered in the ame queue, a it i the cae for the queue CO1, M1 and M2, the topological ort algorithm 101 know that the meage having the older timetamp ha alway to be proceed before the meage with the younger timetamp On the right hand of FIG. 11 for thoe queue having dependent queue entrie the queue element are hown a directed graph, where each queue entry i repre ented by a node of the directed graph and the logical dependencie between the node are illutrated by arrow When the orting algorithm evaluate logical dependencie of a pecific meage, it analye all queue where the meage ha regitered. For example, when ana lyzing the third meage 330 (Ch/CO1), the queue CO1, M1 and M2 are analyzed to determine the logical depen dencie. In queue CO1 and M1, dependencie on the firt meage 310 (Cr/CO1) are determined. In queue M2, a dependency on the econd meage 320 (Cr/CO2) i deter mined. A a conequence, the third meage 330 cannot be proceed before the econd meage When thi algorithm i applied to all meage that have regitered in the cheduler 100 the reult i that the firt and forth meage 310, 340 (Cr/CO1, Cr/CO3) have no dependencie and, therefore, can be immediately proceed. Wherea the econd and third meage 320, 330 have to wait in the queue. For example, the independent meage are lited in the pool 110 a decribed in FIG FIG. 12 how an alternative embodiment of the invention In the example of FIGS all queue informa tion of the cheduler 100 i tored in the memory 910. In cae the cheduler 100 crahe for any reaon or the further computer ytem 900 uffer a break down, the queue information would be lot cauing inconitencie with queue in other computer ytem of the computer ytem network To overcome thi problem, a meage (e.g., firt meage 301) that i ent to the cheduler 100 from any application (e.g., firt application 201) may alo be perited in periting mean, uch a, for example, a local databae 501. That i, in cae of a crah or a communication failure of the ending ytem the meage i alo ent to the local databae 501 and i tored in the local databae In cae of uccefully ending the meage to the remote ytem the meage i perited in the local databae of the receiving ytem. In cae the cheduler 100 crahe it can reload the queue information after it retart from the databae 500 into the memory 910. Thi i advantageou with repect to tranactional ecurity in application ytem becaue the retart mechanim avoid a lo of meage A decribed previouly, in one implementation, the cheduler (e.g., local cheduler 101) can be reponible for queuing meage of one computer ytem 901. For example, the local cheduler 101 i an optional component in the firt computer ytem 901. The local cheduler 101 i

20 US 2006/ A1 Jun. 15, 2006 interfaced to the firt application 201 in the firt computer ytem 901 and i illutrated by a dahed box In another implementation, the cheduler can be reponible for queuing meage of a plurality of computer ytem in a network (e.g., central cheduler 100). In thi cae, the variou computer ytem 900, 901, 902, 903 are declared at the central cheduler 100. The declaration of the variou computer ytem make the local ytem known to the central cheduler 100. The declaration may include information about the detination and/or the interface to be ued for remote call from the central cheduler 100 into the local ytem When, after a period of temporary non-availability, the central cheduler 100 i available again it till know the local computer ytem that can be relevant for queue reconciliation In one embodiment, the local ytem may have local cheduler (e.g., local cheduler 101). For example, a meage that i created in a local computer ytem 901 may regiter itelf at the correponding local cheduler 101 of the local ytem 901. The regitration may occur ynchronouly at the local cheduler 101 providing to the local cheduler all information that i needed to guarantee the correct order of execution. For example, thi information can include all queue identifier of queue that the meage depend on. Additional information may be regitered. Such a, informa tion for authority-check, login-information, hortcut for execution, etc. The additional information may be ued for a remote login allowing the central cheduler 100 to execute a meage in a correponding local ytem. The local cheduler 101 may provide a timetamp to the meage. The timetamp functionality can be implemented a a counter or a a value of any function that i trictly monotonic over time. Alternatively, the timetamp may be provided by a central time tamping ervice in the computer network The meage can then be perited in the local databae 501 aociated with the local ytem 901 where it wa created. 0079) When, for example, the central cheduler 100 i not available over a pecific time interval becaue of, for example, a break down or network problem, the local cheduler may reend meage that were generated during the pecific time interval to the central cheduler 100 once it i available again. For example, a meage can include a unique identifier, which allow the central cheduler 100 to recognize whether the meage wa already ent or not in cae the meage i reent In another embodiment, the central cheduler 100 may retrieve perited meage directly from the peri tence mean (e.g., databae 501) once the central cheduler 100 become available again by, for example, uing remote function call Once a meage i perited, the tranaction that generated the meage may notify the central cheduler 100 that the meage ha been perited. In cae the central cheduler 100 i not available, the local cheduler 101 may be notified. Only then a meage can be executed In cae uch a notification get lot, for example, a timeout may pecify, when the cheduler ha to look for perited meage. Any perited meage i valid becaue only the notification got lot but the correponding tranac tion ha been executed. If a tranaction i not executed correctly, a rollback may have occurred and no meage get perited. 0083) Each local ytem 901, 902, 903 may have the ame availability a the correponding local cheduler. In thi cae, the local ytem i tarted and topped together with it local cheduler In a further implementation, a meage that i created in a local ytem 901 may be ent together with the regitration information to the central cheduler 100. In thi cae, the central cheduler 100 add a timetamp and the meage data (e.g., firt meage 301) i perited (dahed arrow) in a databae 500 aociated with the computer ytem 900 running the central cheduler 100. Then, the central cheduler 100 return control to the local ytem 901 that generated the meage When, after the pecific time interval of non availability, the central cheduler 100 become available again, perited meage are read in the order of their timetamp from the torage location where the meage had been perited. Timetamp which were not provided by the central cheduler 100 but created in a local ytem at a time when the central cheduler 100 wa unavailable may either be tranformed to central cheduler timetamp (e.g., by calculating the time difference between the ytem) or may be replaced by a new valid central cheduler timetamp at the time of the meage tranfer During a retart of the central cheduler 100, me age that are read in from the peritence databae() can be executed and new meage can already be regitered. At the time when all perited but not yet executed meage have been read from the peritence databae(), the central cheduler 100 i again in ync with the local ytem FIGS. 13A and 13B illutrate a flowchart of a firt method 400 decribing in detail meage queuing with a dependency reolution mechanim of the cheduler 100 in cae of a lo of queue data in the memory 910 or in cae of a network malfunction. FIG. 13A how the firt portion of the flow chart and FIG. 13B the econd portion The central cheduler 100 receive 405 and regi ter 415 the firt meage. Then the central cheduler 100 receive 420 and regiter 430 the econd meage. The meage may have been created by correponding tranac tion of the firt application 201. Advantageouly, before the meage are regitered in the correponding queue of the central cheduler 100, they are perited 410, 425 in per iting mean a decribed under FIG. 12. For example, the peritence may occur in the aociated local databae 501 or in the databae 500. A meage tay in the peritence mean until the meage i finally executed. Then, the central cheduler 100 notifie the correponding peritence mean (e.g., local databae 501) to remove the executed meage. It i aumed that, after having regitered the econd meage, the central cheduler 100 become unavail able either becaue of a ytem crah or a memory malfunc tion or becaue of network problem A local ytem (e.g., the firt computer ytem 901) may continue to generate meage while the central Sched uler 100 i unavailable. For example, the firt application

21 US 2006/ A1 Jun. 15, generate a further meage while the central cheduler 100 i down and, therefore, unavailable to regiter the meage In a firt implementation the local cheduler 101 reend the further meage to the central cheduler 100 until the central cheduler 100 become available again after it retart 435. Then the further meage i finally received 437 by the central cheduler 100 and get regitered 438 in the correponding queue. The further meage may be perited 427 in the local databae 501 before the central cheduler 100 i retarted 435. Alternatively, the meage may be perited 427 in the databae 500 that i aociated with the central cheduler 100 after the further meage ha been received 437. Further, the firt and econd meage are tranferred 455 to the central cheduler 100 in cae they got dicarded from the memory 910. In cae of a network interruption, the firt and econd meage may till reide in the memory 910 and a tranfer from the peritence mean may not be neceary. The tranferred meage get regi tered in the correponding queue of the central cheduler 100 according to their original timetamp. In other word, the central cheduler 100 merge 460 the tranferred me age with other meage, uch a, for example, the third meage that ha been received 440 and regitered 450 ince the central cheduler' retart FIGS. 14A and 14B how a implified flow chart of an alternative econd method 600, where the tep 605, 610, 615, 620 and 625 correpond to the tep 405, 410, 415, 420 and 425 of the firt method 400. In the alternative method 600, the further meage get a timetamp (e.g., from the local cheduler 101 or another timetamp ervice) and i perited 627 in the local databae 501. When the central cheduler 100 become available again after a retart, the perited firt, econd and further meage are tran ferred 655 to the central cheduler according to one of the implementation decribed under FIG. 12. In cae of a network interruption the central cheduler may till have the firt and econd meage regitered in the correponding queue and only the further meage need to be tranferred from the local data bae to the central cheduler. The tranferred meage get regitered in the correponding queue of the central cheduler 100 according to their original timetamp. In other word, the central cheduler 100 merge 660 the tranferred meage with other me age, uch a, for example, the third meage that ha been received 640 and regitered 650 ince the central cheduler' retart When the central cheduler 100 retart 435, 635 after a break down it can generate a retart timetamp for itelf. Each meage that i received by the central cheduler after the retart receive a timetamp that i younger than the retart timetamp. The central cheduler know that only meage need to be tranferred 455, 655 that have a timetamp that i older than the retart timetamp. The central cheduler 100 merge 460, 660 the tranferred me age with other meage that may have been received after the retart timetamp according to their timetamp Once the central cheduler 100 i in ync with the local ytem, the reolution of logical dependencie i executed by identifying 465, 665 the logical dependencie and releaing 470, 670 the meage a decribed under FIGS. 6 to ) Embodiment of the invention can be implemented in digital electronic circuitry, or in computer hardware, firmware, oftware, or in combination of them. The inven tion can be implemented a a computer program product, i.e., a computer program tangibly embodied in an informa tion carrier, e.g., in a machine readable torage device or in a propagated ignal, for execution by, or to control the operation of data proceing apparatu, e.g., a program mable proceor, a computer, or multiple computer. A computer program, Such a the cheduler decribed above, can be written in any form of programming language, including compiled or interpreted language, and it can be deployed in any form, including a a tand alone program or a a module, component, Subroutine, or other unit Suitable for ue in a computing environment. A computer program can be deployed to be executed on one computer or on multiple computer at one ite or ditributed acro multiple ite and interconnected by a communication network Method tep of the invention can be performed by one or more programmable proceor executing a computer program to perform function of the invention by operating on input data and generating output. Method tep can alo be performed by, and apparatu of the invention can be implemented a, pecial purpoe logic circuitry, e.g., an FPGA (field programmable gate array) or an ASIC (appli cation pecific integrated circuit) Proceor uitable for the execution of a computer program include, by Way of example, both general and pecial purpoe microproceor, and any one or more proceor of any kind of digital computer. Generally, a proceor will receive intruction and data from a read only memory or a random acce memory or both. The eential element of a computer are at leat one proceor for executing intruction and one or more memory device for toring intruction and data. Generally, a computer will alo include, or be operatively coupled to receive data from or tranfer data to, or both, one or more ma torage device for toring data, e.g., magnetic, magneto optical dik, or optical dik. Information carrier Suitable for embodying computer program intruction and data include all form of non Volatile memory, including by way of example emi conductor memory device, e.g., EPROM, EEPROM, and flah memory device; magnetic dik, e.g., internal hard dik or removable dik; magneto optical dik; and CD ROM and DVD-ROM dik. The proceor and the memory can be Supplemented by, or incorporated in pecial purpoe logic circuitry To provide for interaction with a uer, the invention can be implemented on a computer having a diplay device, e.g., a cathode ray tube (CRT) or liquid crytal diplay (LCD) monitor, for diplaying information to the uer and a keyboard and a pointing device, e.g., a moue or a trackball, by which the uer can provide input to the computer. Other kind of device can be ued to provide for interaction with a uer a well; for example, feedback provided to the uer can be any form of enory feedback, e.g., viual feedback, auditory feedback, or tactile feedback; and input from the uer can be received in any form, including acoutic, peech, or tactile input The invention can be implemented in a computing ytem that include a back end component, e.g., a a data erver, or that include a middleware component, e.g., an

22 US 2006/ A1 Jun. 15, 2006 application erver, or that include a front end component, e.g., a client computer having a graphical uer interface or a Web brower through which a uer can interact with an implementation of the invention, or any combination of Such back end, middleware, or front end component. The com ponent of the ytem can be interconnected by any form or medium of digital data communication, e.g., a communica tion network. Example of communication network include a local area network (LAN) and a wide area network (WAN), e.g., the Internet The computing ytem can include client and erver. A client and erver are generally remote from each other and typically interact through a communication net work. The relationhip of client and erver arie by virtue of computer program running on the repective computer and having a client-erver relationhip to each other A number of embodiment of the invention have been decribed. Neverthele, it will be undertood that variou modification may be made without departing from the pirit and cope of the invention. What i claimed i: 1. A computer program product configured to proce meage of at leat one of a plurality of computer ytem in a further computer ytem of the plurality of computer ytem, the computer program product having a plurality of intruction that when loaded into a memory of the further computer ytem caue at leat one proceor of the further computer ytem to execute the following tep: receiving a firt meage from one of the plurality of computer ytem; regitering the firt meage in a firt queue; receiving a econd meage from one of the plurality of computer ytem, the econd meage having a logical dependency on the firt meage; regitering the econd meage in a econd queue and in the firt queue, wherein the queue entry of the econd meage in the firt queue occur after the queue entry of the firt meage in the firt queue; identifying the logical dependency of the econd meage on the firt meage by the order of the correponding queue entrie in the firt queue; and releaing the firt meage for proceing before releaing the econd meage according to the logical depen dency. 2. The computer program product of claim 1, configured to caue the at leat one proceor to execute the further tep: receiving a third meage from one of the plurality of computer ytem after having received the firt and econd meage, the third meage being logically independent from the firt and econd meage; regitering the third meage in a third queue; and releaing the third meage for proceing before the Second meage. 3. The computer program product of claim 2, configured to caue a further proceor of the further computer ytem to releae the third meage to be proceed in parallel with the firt meage. 4. The computer program product of claim 1, wherein the regitering tep provide a unique timetamp for each received meage and the queue entrie are regitered trictly monotonou over time according to the timetamp of the correponding meage. 5. The computer program product of claim 1, wherein the identifying tep ue a topological ort algorithm to identify the logical dependency between the firt and econd me age within the firt queue. 6. The computer program product of claim 5, wherein the topological ort algorithm i applied to further queue to which a meage ha regitered to identify further logical dependencie. 7. The computer program product of claim 1, wherein the logical dependency i defined by an object that i affected when the firt meage i proceed and i affected when the econd meage i proceed. 8. The computer program product of claim 1, compriing further intruction that caue the at leat one proceor to execute the tep of: after a retart of the computer program, receiving a plurality of perited meage from peritence mean that correpond to the plurality of meage regitered before the retart; and merging the plurality of the perited meage with meage that are already regitered in correponding queue after the retart by regitering the perited meage in the correponding queue o that all logical dependencie are taken into account. 9. A method for proceing meage of at leat one of a plurality of computer ytem in a further computer ytem of the plurality of computer ytem, compriing the tep: receiving a firt meage from one of the plurality of computer ytem; regitering the firt meage in a firt queue; receiving a econd meage from one of the plurality of computer ytem, the econd meage having a logical dependency on the firt meage; regitering the econd meage in a econd queue and in the firt queue, wherein the queue entry of the econd meage in the firt queue occur after the queue entry of the firt meage in the firt queue; identifying the logical dependency of the econd meage on the firt meage by the order of the correponding queue entrie in the firt queue; and releaing the firt meage for proceing before releaing the econd meage according to the logical depen dency. 10. The method of claim 9 compriing the further tep: receiving a third meage from one of the plurality of computer ytem after having received the firt and econd meage, the third meage being logically independent from the firt and econd meage; regitering the third meage in a third queue; and releaing the third meage for proceing before the Second meage. 11. The method of claim 10, wherein the third meage i releaed before the econd meage to be proceed in parallel with the firt meage.

23 US 2006/ A1 Jun. 15, The method of claim 9, wherein the regitering tep provide a unique timetamp for each received meage and the queue entrie are regitered trictly monotonou over time according to the timetamp of the correponding me Sage. 13. The method of claim 9, wherein the identifying tep ue a topological ort algorithm to identify the logical dependency between the firt and econd meage within the firt queue. 14. The method of claim 13, wherein the topological ort algorithm i applied to further queue to which a meage ha regitered to identify further logical dependencie. 15. The method of claim 9, wherein the logical depen dency i defined by an object that i affected when the firt meage i proceed and i affected when the econd meage i proceed. 16. The method of claim 9, compriing the further tep of: retarting a computer program that already ha performed the receiving meage and regitering meage tep for a plurality of meage; receiving from peritence mean a plurality of perited meage that correpond to the plurality of meage that were regitered before the retarting tep; and merging the plurality of the perited meage with meage that are already regitered in correponding queue after the retarting tep by regitering the per ited meage in the correponding queue o that all logical dependencie are taken into account. 17. A computer ytem configured to proce meage of at leat one of a plurality of computer ytem, compriing: a memory toring a computer program product according to claim 1; and at leat one proceor configured to execute the computer program.