Abstract:
A multinode activation and termination method and system A method and system is provided for invoking multiple parallel instances of the same node. First, a multinode is defined that allows for multiple parallel activation of the node. At run time, a determination is made of the number of nodes to be activated based on an activation rule. The multinodes are then executed. Each multinode can be provided with different input data for execution, thereby allowing one to fine tune the input and attributes of each node. A termination rule is utilized to determine when the execution of the multinode is completed. When the execution of the multinode is complete, a successor node is then executed. When the execution of the multinode is not complete, processing continues on the multinode.

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to electronic business technology, and more particularly, to business process automation and to a multinode activation and termination method and system. 
     BACKGROUND OF THE INVENTION 
     Workflow management is a rapidly evolving technology that many businesses in a variety of industries utilize to handle business processes. A business process, as defined by the Workflow standard—Terminology &amp; glossary, Technical Report WFMC-TC-1011, Worflow Management Coalition, June 1996. Versions 2.0., is simply a set of one or more linked activities that collectively realize a business objective or a policy goal, typically within the context of an organizational structure defining functional roles and relationships. A workflow is defined as the automation of a business process, in whole or in part, during which documents, information, or activities are passed from one participant to another, according to a set of predefined rules. A workflow management system (WfMS) defines, creates, and manages the execution of workflows. 
     Examples of workflow software include BusinessWare software, available from Vitria Technology, Inc. of Sunnyvale, Calif., Inconcert software, available from TIBCO Software, Inc. of Palo Alto, Calif., MQ Series software, available from International Business Machines Corporation (IBM), of Armonk, N.Y., and Staffware 2000, available from Staffware of Berkshire, United Kingdom. 
     There are hundreds of commercial workflow management systems (WfMSs), which are available on the market, as well as many research prototypes. While each system has a different process model, most of them share the same basic concepts. In one example, a process is described by a directed graph that has four different kinds of nodes. 
     Work nodes (also called service nodes) represent the invocation of activities (also called services), which are assigned for execution to a human or automated resource. Route nodes are decision points that route the execution flow among nodes based on an associated routing rule. Start nodes denote the entry point to the process. Typically, only one start node is allowed in a process. Complete nodes denote termination points. 
     There are many business processes in which an activity needs to be executed multiple times in parallel. For example, a restaurant brokering service may need to request the rates and availability from several restaurants that provide on-line access to this type of information. The request node that requests rates and availability may need to be repeated for all the restaurants that meet a particular criteria (e.g., in a particular vicinity). 
     In some of these applications, the exact number of activations for the node is known at the time when the process definition is created. For example, in a small town, the number of restaurants may be relatively static. However, there are other applications where the exact number of parallel activations is not known at the time when the process definition is generated. For example, in a large metropolitan area, the number of restaurants may vary widely since many restaurants may open for business or close for business on any given day. 
     To model such a business process with traditional process models, the process developer is required to employ very complex process definitions to attempt to account for all the possible cases. For example, the developer may “guess” a maximum number of parallel activities that need to be activated in executions of the business process. In the example above, a process developer may assume that there will be at most twenty (20) restaurants. The developer then models a corresponding number of nodes in the workflow definition.  FIG. 7  illustrates an exemplary process definition that has a request node for each of the twenty restaurants. Unfortunately, these complex process definitions are difficult to specify and even more difficult to maintain. Furthermore, this approach is limited since when there are more restaurants than the assumed maximum number (e.g., a number greater than twenty in this case), there is no provision in the process definition to handle such a case. 
     Some prior art approaches allow the multiple activation of services for each node, where the number of instances is based on the number of available resources. The Process Manager product available from Hewlett-Packard (HP) of Palo Alto, Calif., the assignee of the present invention, is an example of such an approach. In this approach, multiple activities can be executed in parallel within a work node. However, it is noted that the number of activities that are executed in parallel is always equal to the number of resources that are available for execution of that activity. In other words, no other criteria for the selection of the number of parallel activations are possible. 
     Furthermore, each activity is assigned to a different resource. Also, all the activities have the same input data. Moreover, the attributes of the node (e.g., the service selection, resource selection, security, exception handling specification) are the same for every activity execution within the work node. As can be appreciated, such a solution lacks flexibility. In fact, it would instead be desirable to have different resource selection criteria, different data, and different security and exception handling criteria depending on the purpose of the activity execution. 
     Consequently, it would be desirable to have a mechanism that allows for multiple executions, where the input can be varied for each execution, and the attributes of the execution can be varied for each execution, thereby providing a flexible solution. 
     Based on the foregoing, there remains a need for a multinode method and system having activation rules and termination rules that overcomes the disadvantages set forth previously. 
     SUMMARY OF THE INVENTION 
     According to one embodiment of the present invention, a method and system for processing workflows having at least one multinode (also referred to herein as a multi-service node) is described. 
     One aspect of the present invention is the provision of resource-based multinode acitvation rules. 
     Another aspect of the present invention is the provision of variable-based multinode acitvation rules. 
     Another aspect of the present invention is the provision of multinode termination conditions, where all nodes in the multinode must complete processing before processing for the multinode is terminated. 
     Another aspect of the present invention is the provision of termination conditions where less than all the nodes need to complete processing before processing for the multinode is terminated. 
     According to one embodiment, a multinode activation and termination method and system is provided for allowing multiple parallel instances of a same node to be invoked. First, a multinode is defined that allows for multiple parallel activation of a work node. At run time, a determination is made of the number of work nodes to be activated based on an activation rule. The work nodes are then executed. Each work node can be provided with different input data for execution, thereby allowing one to fine tune the input and attributes of each work node. A termination rule is utilized to determine when the execution of the multinode is completed. When the execution of the multinode is complete, a successor node is then executed. When the execution of the multinode is not complete, processing continues within the multinode. 
     Other features and advantages of the present invention will be apparent from the detailed description that follows. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention is illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings and in which like reference numerals refer to similar elements. 
         FIG. 1  illustrates an architecture for processing nodes according to one embodiment of the present invention can be utilized. 
         FIG. 2  is a block diagram of a multi-service node mechanism according to one embodiment of the present invention. 
         FIG. 3  is a flow chart illustrating the processing steps related to multi-service node activation that are performed by the multi-service node mechanism of  FIG. 2  in accordance with one embodiment of the present invention. 
         FIG. 4  is a flow chart illustrating the processing steps related to multi-service node termination that are performed by the multi-service node mechanism of  FIG. 2  in accordance with one embodiment of the present invention. 
         FIG. 5  is an exemplary restaurant reservation workflow in which the multinode activation by resource may be utilized and in which multinode termination in accordance with one embodiment of the present invention may be utilized. 
         FIG. 6  is an exemplary travel reservation workflow in which the multinode activation by variable may be utilized and in which multinode termination in accordance with an alternative embodiment of the present invention may be utilized. 
         FIG. 7  illustrates an exemplary prior art process definition. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     A method and system for multinode activation and termination are described. In the following description, for the purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It will be apparent, however, to one skilled in the art that the present invention may be practiced without these specific details. In other instances, well-known structures and devices are shown in block diagram form in order to avoid unnecessarily obscuring the present invention. 
     Architecture  100   
       FIG. 1  illustrates an architecture  100  for processing multinodes according to one embodiment of the present invention. The architecture  100  includes a workflow engine  110  that can, for example, be an application that executes on a processor. The workflow engine  110  retrieves a process definition  114  (e.g., a flowchart). The workflow engine  110  then determines the first work node to execute. Next, the workflow engine  110  determines (e.g., reads) an activity corresponding to the first work node. 
     Then, the workflow engine  110  determines a resource rule corresponding to the activity. Preferably, the workflow engine  110  queries a resource executive  130  (e.g., the Process Manager product available from Hewlett-Packard (HP) of Palo Alto, Calif., the assignee of the present invention) to obtain a single resource or list of resources. An example of a single resource is the name of an individual in the organization, who is responsible for performing the activity. An example of a list of resources is a list of names of individuals in the organization, who are responsible for performing the activity. 
     Once the workflow engine  110  receives the list of resources, the workflow engine  110  assigns the activity to a particular resource  134  (e.g., resourceA, . . . , resourceN). When the resource  134  completes the activity, the resource  134  notifies the workflow engine  110  of completion. The workflow engine  110  then retrieves the process definition  114  to determine the next node in the workflow for processing. The next work node is then processed in a manner similar to the first work node. This process is repeated for all work nodes until the all nodes in the workflow are processed. 
     The workflow engine  110  can include a multinode mechanism  150  for processing multinodes. It is noted that the multinode mechanism  150  is preferably implemented as part of the workflow engine  110  (e.g., incorporated in the workflow engine  110 ). Alternatively, the multinode mechanism  150  can be implemented as a module that is separate from the workflow engine  110 . In this case, the multinode mechanism  150  communicates with the workflow engine  110 , but is not part of the workflow engine  110 . 
     The multinode mechanism  150  (also referred to herein as a multinode handling facility) handles activation of the multinode and termination of the multinode. In one embodiment, the multinode mechanism  150  determines the number of nodes in the multinode to be activated based on an activation rule, executes the nodes in the multinode; determines when the execution of the multinode is completed based on a termination rule, and when the execution of the multinode is complete, executing a successor node. The multinode mechanism  150  is described in greater detail hereinafter with reference to  FIG. 2 . 
     Multinode Mechanism  150   
       FIG. 2  is a block diagram of a multinode mechanism  150  according to one embodiment of the present invention. The multinode mechanism  150  includes a multinode determination unit (MDU)  210  for receiving a node definition  214  and determining whether the current node is a normal work node or a multinode. The multinode mechanism  150  also includes an activation facility  220  for receiving an activation rule  224  and based thereon for determining whether activation is by resource (resource-based activation) or by variable (variable-based activation). 
     The multinode mechanism  150  also includes a resource-based activation facility  240  for processing activation by resource and a variable-based activation facility  250  for processing activation by variable. 
     The resource-based activation facility  240  includes a resource rule execution unit (RREU)  244  for executing the resource rule of the multinode. For example, the resource rule may be specified in a service node tag of the multinode description. The resource-based activation facility  240  further includes a new instance generation unit (NIGU)  248  for starting new instances of the multinode for each new resource in the resource list. 
     The variable-based activation facility  250  includes a variable name reader  254  for reading the variable name V. For example, variable V may be of type vector or list. The variable-based activation facility  250  further includes a new instance generation unit (NIGU)  258  for starting new instances of the multinode for each new element in the vector or list identified by the variable name. 
     Multi-Service Node Activation Processing 
       FIG. 3  is a flow chart illustrating the processing steps related to multi-service node activation that are performed by the multi-service node mechanism of  FIG. 2  in accordance with one embodiment of the present invention. In step  310 , a new node is scheduled for execution by the workflow engine  110 . In step  320 , the workflow engine  110  reads the node definition. In decision block  330 , a determination is made based on the node definition whether the current node is a multi-service node or a non-multi-service node. 
     When the current node is a multi-service node, processing proceeds to processing step  340 . When the current node is not a multi-service node, processing proceeds to processing step  334 , where normal node activation occurs. Normal node activation procedure is well-known to those of ordinary skill in the art and is not discussed further herein. 
     In step  340 , the workflow engine  110  reads the activation rule. The activation rule can, for example, be specified by an activation tag in a mark-up language (e.g., XML) service description. In decision block  350 , a determination is made whether the activation is by resource (i.e., resource-based activation) or by variable (i.e., variable-based activation). 
     In step  360 , the workflow engine  110  executes the resource rule of the service node as specified in the SERVICE_NODE tag of the multi-service description. In step  364 , the workflow engine  110  starts a new instance of the service node as specified in the SERVICE_NODE tag of the multi-service description. The new instance is assigned to the current resource. In decision block  368 , a determination is made whether there are more resources to which a new instance of a service node should be assigned. In other words, the decision block determines whether all resources have been processed. When all resources have been processed, processing ends. When there are more resources to be processed, processing proceeds to step  364 . It is noted that steps  364  and  368  are repeated for each resource r returned by the resource rule execution. Hence, in this case the number of service nodes activated is equal to the number of available resources for executing the node. 
     In step  370 , the workflow engine  110  reads the variable name V. The variable name V can be, for example, of type vector or list. In step  374 , the workflow engine  110  starts a new instance of the service node as specified in the SERVICE_NODE tag of the multi-service description. The value contained in the position i of vector V is passed as an input parameter to the service node. 
     In decision block  378 , a determination is made whether there are more elements in vector V to be processed. In other words, the decision block determines whether all elements in vector V have been processed. When all elements in vector V have been processed, the processing ends. When there are more elements to be processed, processing proceeds to step  374 . It is noted that steps  374  and  378  are repeated for each element i in vector V. 
     Multi-Service Node Termination Processing 
       FIG. 4  is a flow chart illustrating the processing steps related to multi-service node termination that are performed by the multi-service node mechanism of  FIG. 2  in accordance with one embodiment of the present invention. In step  410 , the execution of a node is completed. In step  420 , the workflow engine  110  reads a definition of the completed node. In decision block  430 , a determination is made whether the node is part of a multi-service node. 
     When the current node is part of a multi-service node, processing proceeds to processing step  440 . When the current node is not part of a multi-service node, processing proceeds to processing step  450 , where normal node termination occurs. Normal node termination procedure is well-known to those of ordinary skill in the art and is not discussed further herein. 
     In step  440 , the workflow engine  110  evaluates the termination condition that is specified in the TERMINATION tag. In decision block  460 , a determination is made whether the termination condition is true. When the termination condition is true, in step  470 , the multi-service node is completed. Otherwise, when the termination condition is false, the multi-service node is not completed, and processing ends (i.e., the multiservice node continues to execute). 
     Exemplary Restaurant Reservation Workflow 
       FIG. 5  is an exemplary restaurant reservation workflow  500  in which multinode activation by resource may be utilized and in which multinode termination in accordance with one embodiment of the present invention may be utilized. The process definition  500  has a start node  510  (e.g., StartNode 2 ), a first work node  520  (e.g., ProcessCustomerReqeust2) that processes the customer request, a multinode  530  (e.g., RestaurantRateRequest), a second work node  540  (e.g., NotifyCustomer 2 ) that notifies the customer of the rates of the different restaurants, and a complete node  550 (e.g., CompleteNode 2 ). 
     In this restaurant reservation workflow  500 , all available restaurants need to be contacted for price information. It is noted that the restaurants are considered to be resources in this example. Accordingly, the multinode  530  may be activated by resource (steps  360 - 368  of  FIG. 3 ). 
     It is further noted that termination for multinode  530  can be based upon the condition that information from all the restaurants has been received. In other words, the multinode  530  terminates when all work nodes in the multinode  530  have been completed according to one embodiment of the present invention. 
     Exemplary Travel Reservation Workflow 
       FIG. 6  is an exemplary travel reservation workflow  600  in which multinode activation by variable of the present invention may be utilized and in which multinode termination in accordance with an alternative embodiment of the present invention may be utilized. 
     The process definition  600  has a start node  610  (e.g., StartNode 3 ), a first work node  620  (e.g., FlightHotelAvailability) that checks flight availability and hotel availability, a multinode  630  (e.g., RequestVisa), a route node  640  (e.g., RouteNode 5 ), a work node  650  (e.g., BookTravel), a complete node  660  (e.g., CompleteNode 3 ), and a complete node  670  (e.g., CompleteNode 4 ). The route node  640  routes processing to the work node  650  (e.g., BookTravel) when all the visas are granted. The route node  640  routes processing to the complete node  670  (e.g., CompleteNode 4 ) when some of the visas are not granted. 
     The multinode  630  is employed to request a visa for all tourists in a group. Accordingly, activation of the multinode  630  may be accomplished by variable since the request for visas depends on the number of tourists in the group. It is noted that the consulates that release visas to the tourists are considered to be the resources in this case. The activation cannot be based on the number of resources (i.e., consulates), since there is no correlation between the number of tourists that need visas and the number of available resources (i.e., consulates that can release visas). Instead, a variable in the workflow instance can be utilized to indicate the number of visas that need to be requested in accordance with the present invention. 
     With this workflow, a multinode termination condition in accordance with an alternative embodiment of the present invention may be utilized. For example, workflow execution can proceed from the multinode  630  to the route node  640  when either all the visas have been received or when at least one visa has been declined. This example illustrates a case where the multinode may be terminated even before all work nodes have been completed. 
     In the foregoing specification, the invention has been described with reference to specific embodiments thereof. It will, however, be evident that various modifications and changes may be made thereto without departing from the broader scope of the invention. The specification and drawings are, accordingly, to be regarded in an illustrative rather than a restrictive sense.