DYNAMIC CREATION OF WORKFLOWS FROM DETERMINISTIC MODELS OF REAL WORLD PROCESSES

Abstract: A workflow generated from a declarative model of a real world process represents the procedural steps to accomplish the process. In one embodiment, the declarative model may include a first number of state nodes and a second number of task nodes interconnected with the state nodes. In such cases, generating a workflow may be accomplished by choosing one of a number of paths through th emodel, each of the paths comprising an alternating series of one or more of the state nodes and one or more of the task nodes with any predecessor state node in one of the paths representing a precondition for a subsequent task node along the one of the paths and any following state node of the subsequent task node along the one of the paths representing a result of applying one or more actions that correspond to that task node. As part of a computer assisted scheduling system, the model may be configured to receive updates reflecting changes in the real-world manufacturing environment. Such changes may represent completed tasks, and/or a change in the availability of one or more resources represented in the model.

Description: DYNAMIC CREATION OF WORKFLOWS FROM DETERMINISTIC MODELS OF REAL WORLD PROCESSES FIELD OF THE INVENTION The present invention involves the creation of procedural descriptions of real world processes, for example manufacturing processes, from declarative descriptions of the environment in which the processes are performed. BACKGROUND Within manufacturing environments, the questions of deciding what products to produce (assuming the environment is capable of producing more than a single product), when to produce them, how to produce each and whether even to accept new orders for different products must all be weighed against the realities of the various constraints imposed upon and within the environment. Workflow systems may and have been used to specify how products should be produced. In general, workflows represent procedural steps to accomplish a process (e.g., a product production process). In traditional workflow systems, different workflows are individually defined in advance, and a particular one of these predefined workflows is selected and run, according to the product being produced. Thus, in such systems one must decide whether to create only a few, inflexible workflows, or a number of different workflows. For the first scenario, although having only a few workflows may make the maintenance thereof relatively less burdensome (e.g., as compared to situations where a large number of workflows must be maintained), it also means that one will be forced to make due with workflows that are not necessarily optimized for all environmental conditions. In the second scenario, although have more workflows may allow for an optimum one to be selected, it does make the selection process more difficult and also increases the maintenance burden. The problem inherent in these approaches may be further exacerbated where the manufacturing environment undergoes not infrequent changes. SUMMARY OF THE INVENTION Presented herein is a solution to the dilemma posed above. Briefly, in accordance with the present invention, workflows can be generated from a declarative model of a real world environment. Indeed, one advantage of the present scheme is that multiple workflows can be generated from a single model, e.g., whenever environmental conditions are changed. In one particular embodiment, the declarative model may include a first number of state nodes and a second number of task nodes interconnected with the state nodes. In such cases, generating a workflow may be accomplished by choosing one of a number of paths through the model, each of the paths comprising an alternating series of one or more of the state nodes and one or more of the task nodes with any predecessor state node in one of the paths representing a precondition for a subsequent task node along the one of the paths and any following state node of the subsequent task node along the one of the paths representing a result of applying one or more actions that correspond to that task node. In general though, any of a number of model representations may be used. Thus, generating a workflow may be accomplished by choosing any one of a plurality of feasible routes for completion of the process defined by the model; by choosing an optimal one of a plurality of routes for completion of the process defined by the model; or by choosing one of a plurality of routes defined by the model according to one or more user-defined criteria for route selection. The routes so chosen may define bills of resources for the real world environment defined by the model. New workflows may be generated in response to an update to the model and/or in response to a new job request. In a further embodiment, a workflow is provided. The workflow may include a final product of the manufacturing process as represented by a first state node of a directed graph. Further, the workflow may include one or more manufacturing processes required in the production of the final product and the corresponding preconditions thereto and results produced thereby. The manufacturing processes may be represented by task nodes, and the preconditions thereto and the results produced thereby represented by state nodes. The task nodes and state nodes may be arranged within the directed graph such that inputs to each of the task nodes represent required states therefor and outputs of each of the task nodes represent alternative states produced thereby. In such an arrangement, the first state node may therefor represent the output of one or more of the manufacturing processes represented by one or more of the task nodes. In some cases, at least one of the task nodes may represent the consumption of reusable or non-reusable resources for a manufacturing environment. The state nodes may represent reusable resources and/or consumable resources for the manufacturing environment. The state nodes of the workflow may be arranged in a hierarchy defined by the directed graph so as to comprise a bill of materials for a manufacturing environment. Yet another embodiment of the present invention provides a computer assisted scheduling system. The system includes a model of a real-world manufacturing environment and a scheduler configured to optimize selection of one of a number of paths through the model to provide as a workflow in response to an order for a product produced by the manufacturing environment. Within the system, the model may be configured to receive updates reflecting changes in the real-world manufacturing environment. Such changes may represent completed tasks, and/or a change in the availability of one or more resources represented in the model. Further details of these and other embodiments will be discussed below, however, it should be remembered that these are merely examples of implementations of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS The present invention is illustrated by way of example, and not limitation, in the figures of the accompanying drawings in which like reference numerals refer to similar elements and in which: Figure 1 illustrates a model having task nodes and state nodes organized for use according to an embodiment of the present invention; Figure 2 illustrates a detailed model of a hypothetical print shop environment; Figure 3 illustrates an example of the hierarchical nature of a model having task nodes and state nodes organized for use according to an embodiment of the present invention; Figures 4A, 4B and 4C illustrate a printing process modeled by one or more task nodes according to a desired level of granularity for a model having task nodes and state nodes organized for use according to an embodiment of the present invention; Figure 5 illustrates an example of a scheduling system employing a model having task nodes and state nodes organized according to an embodiment of the present invention; and Figure 6 illustrates a further example of a scheduling system configured in accordance with an embodiment of the present invention. DETAILED DESCRIPTION A method of developing workflows that may find application in a real world environment is described herein. Many of the techniques to be discussed will make reference to a manufacturing environment (and, in particular, a print shop environment) in which similar types of products are produced in similar ways. However, upon review of this specification, those of ordinary skill in the art will recognize that the present scheme may find application in a variety of environments. Therefore, in the following description the illustrated embodiments should be regarded as examples only, and should not be deemed to limit the scope of the present invention. Before describing the scheme in detail, it is helpful to present an overview. The method makes use of a declarative model of the real world environment. The model is used to generate workflows, which are the procedural steps to be followed in accomplishing the process defined by the model. In one embodiment, the model may be regarded as a directed graph made up of state nodes and task nodes. The task nodes and state nodes are interconnected with one another in such a way so as to define one or more paths through the directed graph, with each path defining a route to a completed product. Each of the paths includes an alternating series of one or more of the state nodes and one or more of the task nodes. In some cases, two or more of the paths may share one or more task nodes and/or state nodes. Generating the actual workflows may be accomplished using a scheduler that is permitted to access the model (e.g., to guide a workflow engine in the creation of the workflows). The rules that define the scheduler may, therefor, determine the criteria by which the workflows are produced. In some cases, generating the workflows may involve choosing any of a number of feasible routes defined by the model. However, in other cases, more sophisticated criteria for workflow generation, such as optimizing for cost, value or other (e.g., user-defined) criteria may be specified and workflows generated accordingly. To better understand the above-described method, consider a hypothetical print shop. The print shop includes a number of machines, which are used in the printing of books and similar articles. For example, the print shop includes a number of printers, each of which is capable of producing a document, printed on paper or another material, from a computer-readable file (e.g., a PostScript™ file). In addition, the print shop includes special printers for producing covers. Besides printers, the print shop may include machines for binding the various documents and covers together and other machines for cutting the resulting products to size. In general, all of the products (e.g., books) produced by the print shop are produced using similar processes, but any of the end products may be created in any of a variety of ways. For example depending upon the availability of resources (e.g., the printing, binding and cutting machines) and materials (e.g., paper and ink for the printers, cover stock, etc.) one route may be chosen over another. Thus, the print shop is an example of a homogeneous manufacturing environment. Consider now the following scenario. A number of jobs, perhaps each at various stages of completion and each having certain deadlines for completion, are waiting to be processed. Each job has an associated cost of completion and each completed job has an associated value. Any job not completed on time carries an associated penalty, which may or may not be linear in nature. The task facing the owner of the hypothetical print shop then, is to decide how best to employ the available resources and materials to complete the existing job requests within their designated time frames, while maximizing the derived values from the jobs at the lowest cost. In other words, the print shop owner needs to produce workflows - reports that describe what work to do, when to do it, what resources to apply/utilize, etc., to complete the products. To this task can be added the complication that the print shop owner would like to be able to accept new orders, each of which will carry its own completion time deadlines, costs and values. To assist the print shop owner in these and other matters, the model illustrated in Figure 1 is introduced. Model 10 represents the print shop environment in terms of its bill of materials and bill of resources. It should be appreciated that model 10 may be instantiated as a computer-readable file and may thus be regarded as a virtual representation of the bill of materials and bill of resources. Importantly, the manner in which the inventory items that make up the bill of materials are interconnected to tasks that make up the bill of resources implicitly defines the workflow in the print shop. Before going further, it is helpful to define some terms. A bill of materials, as used herein, is a summary that defines a product structure. More than merely a parts list, a bill of materials provides some idea of how a product is assembled from its constituent parts. In some cases, it may indicate the types and quantities of subassemblies required to produce the product. Although the bill of materials shows the assembly chain for the product, it does not provide any information as to how or when the assembly is to be completed. A bill of resources on the other hand, is a precise list of the available reusable resources that may be employed to assemble the product. For example, the various machines that are located on the print shop floor comprise at least a portion of the print shop's bill of resources. In some cases, outside vendors and suppliers may be part of the bill of resources. Workflows then may be regarded as detailed sets of instructions for how to assemble the product of interest. The workflow specifies the order in which various resources are employed to produce the items on the bill of materials and, hence, acts as assembly instructions for the product. Model 10 is unique in that it integrates a bill of materials with a bill of resources to provide a logical flow structure that may be easily used to identify available workflows. That is, one or more workflows may be regarded as instances of the model. Returning to Figure 1, model 10 includes a collection of state nodes 12 and task nodes 14. The nodes 12 and 14 are interconnected in such a fashion so as to form a state transition graph. That is, task nodes 14 define processes or actions by which predecessor state nodes 12 are transformed to successor state nodes 12. The processes or actions defined by the task nodes 14 are those associated with the available resources of the manufacturing or other process defined by model 10 (e.g., the print shop machines and/or their associated operators for the above print shop example). Thus, in model 10, the state nodes 12 represent intermediate states (or milestones), which have been identified as comprising the bill of materials. All state nodes 12 are the outcome or result of a task node 14. In model 10, state nodes 12 and task nodes 14 always appear in alternating order as one proceeds along a path through the model. Paths are defined as complete routes to a final product and therefore may be regarded as workflows or production plans. Separating the state nodes 12 and task nodes 14 in this fashion provides clarity in the logical semantics of parallel paths. For example, all inputs to a task node 14 represent logical AND requirements. That is, the action associated with a given task node 14 cannot be performed until all of the associated inventory items represented by the state nodes 12 which feed the task node 14 are available. All inputs to a state node 12, on the other hand, represent logical ORs. That is, the inventory item defined by a given state node 12 may be produced by any of the actions associated with any immediate predecessor task node 14. In model 10, state nodes are represented using rectangles while task nodes are represented using ovals. The logical flows that interconnect the nodes are depicted with thick lines representing logical ANDs and thin lines representing logical ORs. Those of ordinary skill in the art will appreciate that model 10 may exist as a virtual representation of the associated manufacturing environment, for example, as may be present in a computer system, a computer-readable storage medium or other database environment. In some cases, model 10 may exist in various component parts in one or more locations of a distributed processing environment. Regardless of its physical location or makeup, however, it should be appreciated that model 10 may be continuously updated with information regarding the real-world manufacturing environment that it represents. In this way, as resources are taken off line or added, model 10 is available to identify new production plans. Within the virtual representation, a task node 14 may be defined with various attributes. For example, each task node may have an associated resource that actually performs the actions represented by the task node. In addition, each task node 14 will have an associated capacity, which may represent the resource's required time for completing the task. Such information may become useful for identifying and avoiding bottlenecks in the manufacturing environment when using model 10 to plan/schedule multiple jobs. The task nodes 14 also have defined predecessors, which in this case are represented by the state nodes 12. As indicated above, however, the attribute list need not include semantic definitions, because the structure of model 10 is such that the node type inherently defines the logical semantics. Other attributes relating to the rules and variants associated with each task node 14 may also be included. State nodes 12 may also have associated attributes. Among these may be an indication of predecessor and/or successor actions/events. Other rules may also form attributes. In general, all nodes of model 10 will have associated rules and each rule may be associated with a successor node of the model. During processing of a real world job in the manufacturing environment represented by model 10, after an action associated with a node has been completed, all rules of the node may be evaluated. If a rule is satisfied, the job may be passed to the successor node associated with the rule. If more than one rule is satisfied, the job may be passed to multiple successor nodes, as represented by the existence of multiple parallel paths in the model 10. Within this representation, each manufacturing process represented by a task node 14 requires certain resources to complete its associated task. These resources may be divided into materials and assets. Materials are those items which can be used only once (i.e., consumables) and are completely used up by the task that uses them. In the print shop environment, examples of materials include paper, toner (for the printers, etc.) and RIPed images, etc. Assets are those resources that are not consumed by the processes that use them. Examples include the actual print machines, the physical plant, operators, etc. (i.e., assets are reusable resources). Both materials and assets may be represented in model 10. To summarize, within the alternating structure of state nodes and task nodes, a predecessor state node in one of the paths (i.e., workflows) represents a precondition for a subsequent task node along that path. Similarly, a state node following a preceding task node along the one of the paths represents a result of applying one or more actions (e.g., manufacturing processes or sub-processes) that correspond to that task node. State nodes and task nodes may be chosen to represent any appropriate level of item or material (in the case of state nodes) or process (in the case of task nodes). In one embodiment, for example, task nodes are introduced into the model to represent significant steps in the processing of materials in the manufacturing environment. It is important to recognize that the manufacturing processes or sub-processes represented by the individual task nodes may correspond to on-site or off-site processes (e.g., where subcontractors or remote manufacturing facilities may be employed). In general then, each task node represents a transformation process for an item or material from a preceding state to a following state. The present model is flexible in that multiple task nodes may be used to represent multiple ways of transforming the item or material from the preceding state to the following state. In other words, different actions or processes (whether performed by humans, machines or both) that lead to the same result may be represented by different task nodes, or, if preferable, by the same task node (e.g., depending upon the granularity of the model chosen to represent a particular manufacturing environment). Indeed, because of this flexibility, the model may be hierarchically arranged such that each task node may be expanded to its own directed graph representation using the model structure described herein. Another interesting feature of the present model is the manner in which the logical semantics of the routes defined by the directed graph are implicit in the model structure itself. For example, all inputs to a task node implicitly represent logical AND requirements. Because of the hierarchy defined by the directed graph, it is axiomatic that the action (or actions) associated with a particular task node cannot be performed until all of the associated materials or items represented by the state nodes which feed that task node are available. The model structure itself makes this logical argument explicit, without having to introduce additional attributes when defining the task node. All inputs to a state node, on the other hand, represent logical ORs. That is, the inventory item or material defined by a particular state node may be produced by any of the actions associated with any immediate predecessor task nodes. Again, the structure of the present model itself defines these relationships, without requiring any additional defining attributes for a state node. Figure 2 presents a fully detailed model 20 of the hypothetical print shop. Model 20 is created using a "top-down" approach, wherein the end product, book 22, is regarded as the outcome of the entire manufacturing process. Model 20 is illustrated using the state node/ task node representation discussed above, where inventory items which make up the bill of materials for a book 22 are represented using rectangles and manufacturing processes which act on the inventory items are represented using ovals. Similar logical flows to those discussed above are inherent in the node structure and are represented in model 20 with thick lines representing logical ANDs and thin lines representing logical ORs. Having decided that book 22 represents the final state (i.e., the output of the print shop manufacturing environment), it is recognized that this state must be the result of some action. In the print shop hypothetical, a book is produced once it is cut to shape; thus, book 22 is the result of one of either of two cutting processes 24 or 26. Notice that model 20 accurately reflects the logical OR nature of these alternative processes. Because all task nodes (by which cutting processes 24 and 26 are represented in model 20) represent actions that are employed on one or more items of a bill of materials, it follows that the inputs to cutting processes 24 and 26 must be represented by state nodes. In this case, before a book can be cut to size by either of cutting processes 24 or 26, some bound material 28 must exist. The bound material 28 is represented in model 20 by the predecessor state node to the task nodes associated with the two cutting processes. Notice that the logical AND requirement for the bound material is also represented in model 20, thus illustrating the need for the bound material 28 to exist before the cutting process may be commenced. If bound material 28 is available, it follows that some binding process must have been applied. Thus, model 20 accommodates the act of binding with task nodes representing two hypothetical alternative binding processes 30 and 32. As shown, these processes act on the predecessor inventory items, namely printed cover 34 and printed body 36. Here, the body of the book 22 refers to all material included within the cover. The printed cover 34 and printed body 36 are represented using appropriate state nodes and the various logical combinations of these items, which may be acted upon by the two binding processes are also illustrated. It should be appreciated, however, that the very node definition will lead to the logical flow illustrated in model 20 and no additional rules need be defined. Both the printed cover 34 and the printed body 36 are the result of independent printing processes. For example, printed cover 34 may be produced by either of cover printing processes 38 or 40, while printed body 36 may be produced by any of printing processes 42, 44, 46 or 48. Thus, appropriate task node representing these various processes are introduced into model 20. Again, the node definition itself has provided an immediate indication of the logical paths available within the manufacturing process. The printing processes 42, 44, 46 and 48 each act upon a RIPed document, although some printing processes may only act upon certain types of RIPed documents. In the hypothetical print shop environment, two types of RIPed documents 50 and 52 may be produced, but each by independent RIPing processes 54, 56 and 58. Thus, these individual inventory items are represented by state nodes assigned to the RIPed documents 50 and 52 and the various RIPing processes 54, 56 and 58 are represented using appropriate task node. The RIPing processes themselves act upon PostScript files 60, represented by an appropriate state node. The PostScript file 60 is produced in response to a retrieval process 62, such as loading a PostScript file. For the cover, no RIPing process is required; thus printed cover 34 is produced directly from a cover PostScript file 64. As for the body PostScript file, cover PostScript file 64 is retrieved by a retrieval process 66. The retrieval processes 62 and 66 are carried out in response to a job request 64. Notice then that model 20 may be created by examining the prerequisites and/or preconditions that must exist in order to execute a particular task, and also determining the actions that are required to arrive at a particular inventory item. These prerequisites and actions are then combined in the logical hierarchy discussed above to form a single model in which the bill of materials (represented by the individual inventory items) and the bill of resources (represented by the collection of actions) are integrated with one another. This procedure may be applied to any manufacturing process, but is especially applicable to homogeneous manufacturing processes such as the print shop example, because a number of products may be produced using similar processes. Although model 20 has not illustrated the integration of consumables, such integration is easily achieved. For example, consumables may be represented as predecessor state nodes to the tasks that consume them. Thus, any or all of the printing processes 42, 44, 46 and/or 48 may draw upon paper, toner and other materials in addition to the RIPed documents. Such materials may be represented as state nodes similar to the RIPed documents 50 and 52, with the exception that the state would have to be defined to indicate its consumable status. Thus, in some embodiments, state nodes representing consumables may be implemented so that their available/not available status must be defined prior to execution of a subsequent task. Preferably, direct feedback from the manufacturing environment may be used to update this status in real time. From the above, it should be apparent that when the present model is used to represent a real-world manufacturing environment, any route through the model to a completed product automatically provides a complete bill of materials and bill of resources for that product. Further, alternative routes (and, hence, alternative bills of materials and bills of resources) are also provided. Thus, a scheduler may make use of the model to assist in the efficient employment of resources within the manufacturing environment. In essence, the scheduler will be required to perform route selection according to rules by which such routes may be chosen to achieve desirable or optimal results. As indicated above, an embodiment of the model may be hierarchical in nature in that one or more task nodes themselves may be further represented by other embodiments of the model. An example of this hierarchical nature is illustrated in Figure 3. In the drawing, a model 70 is illustrated in part. Model 70 is a virtual representation of a manufacturing environment that produces product, as represented by state node 72. Notice that multiple routes are defined by model 70, each route including its own state nodes (shown as rectangles) and task nodes (shown as ovals), some of which may be shared between routes. As explained above, these various routes each define bills of materials and bills of resources that may be used to produce the final product. A particular route (i.e., a workflow) is defined by path 74, which includes task node 76, state node 78 and task node 80. When the process represented by task node 80 operates on the item represented by state node 80, the product represented by state node 72 is produced. Assume now that model 70 is used by a manufacturer that subcontracts the work to be performed by the process represented by task node 76. For the manufacturer, this process is a self-contained unit that ultimately delivers the item represented by state node 78. The manufacturer need not be concerned with the manner in which the item represented by state node 78 is actually produced. Thus, model 70 need only include a representation of the process used to deliver that item (i.e., the granularity of task node 76 is such that an entire subcontracted manufacturing process is represented). The subcontractor employed by the manufacturer, however, is very much concerned with the manufacturing process represented by task node 76 in model 70. Indeed, as shown in Figure 3, the entire subcontracted manufacturing environment may itself be represented by a model 90, which has similar structure to that of model 70. That is, model 90 is a break down of task node 76, created to have the same logical semantic structure between task nodes and state nodes as in model 70. Because model 90 uses the same directed graph approach, should the manufacture who relies upon model 70 to assist in scheduling and other tasks (e.g., order promising, etc.) wish to identify potential bottlenecks, model 90 could be substituted for task node 76 in model 70. In such a case, the scheduler could identify problems that might not otherwise be detectable by the manufacturer. Thus, model 70 is hierarchically arranged such that any task node may be expanded to its own directed graph representation using a similar model structure. Task nodes may also be defined at various levels of granularity as follows. In Figure 4A, a task node 100 represents a transformation process between state nodes 102 and 104. Returning to the print shop metaphor discussed above, task node 100 may represent a document printing process employing any printer and any printer operator. At this level of granularity, the process represented by task node 100 is very coarse, in that the print shop owner is concerned only with the document printing process and not individual printing machines/operators. Figure 4B now illustrates the same document printing process, however, this time task nodes 110, 112 and 114 have been used to represent the process as performed by three different document printing machines. At this level of granularity, a model that included task nodes 110, 112 and 114 would provide different routes to produce the item represented by task node 104, differentiated by printing machine, but not by individual operator. Figure 4C illustrates the same document printing process, however, at a level of granularity that accommodates an identification of several different operators, each capable of using one or more of the possible printing machines. Task nodes 120a - 120i may be included in a model where significant or important differences (e.g., in execution time, capacity, etc.) between operators and/or printing machines is important. Thus, including such detail provides an associated scheduler with multiple possible routes for scheduling production processes. Notice that any of thee or other levels of detail may be accommodated in a model of the manufacturing environment of interest without deviating form the overall structure of the directed graph discussed above. Similar to the manner in which task nodes may be employed at various levels of granularity, state nodes may also be used to represent any desired inventory item in the production process of the manufacturing environment being modeled. Thus, entire subassemblies may be represented in some cases, while in other cases lesser items may be included. Of course, corresponding task nodes will be needed to properly represent the processes used to produce the items represented by the state nodes. Figure 5 illustrates one example of how a scheduler may make use of a model configured in accordance with the teachings presented herein. Note that the scheduler and the model may each be implemented in a computer system having a general-purpose processor and an accompanying memory and input/output system. The scheduler, for example, may represent executable or other code representing a series of computer- readable instructions to be executed by the processor in accordance with the discussion provided below. Similarly, the model may exist as a computer readable database or other file accessible by the processor (e.g., stored in memory). Model 130 is configured as a directed graph to represent a real-world manufacturing environment as described above. Thus, model 130 includes multiple routes between alternating series of state nodes and task nodes to represent various ways in which a product may be produced. Schedule 132 is permitted to access model 130 so as to produce workflows 134 in response to taskings 136. Taskings 136 may represent orders that are being placed for processing within the manufacturing environment, carryovers from previous orders (e.g., that were not completed during previous shifts, etc.) or other requirements. Workflows 134 represent the route through model 130 chosen by scheduler 132 for completion of individual taskings 136. That is, each workflow 138 represents a detailed set of instructions to complete a task (i.e., to produce a product called for by the associated tasking 136). Model 130 may be continually updated to accurately reflect the real-world manufacturing environment, which it represents. Thus, as various operators take breaks or are replaced with new workers, and/or as machines are rotated in and out of service and/or as items in a particular bill of materials are completed or delayed due to equipment failure, model 130 is updated. This allows scheduler 132 to update workflows 134 to account for the changes in the real world environment. To produce workflows 134, scheduler 132 may determine which of the number of possible routes represented in model 130 are available to process each tasking 136 and may then provide work assignments accordingly. For example, scheduler 132 may determine which routes are unavailable by determining which processes represented by task nodes in model 130 are already filled to capacity and decide to schedule new taskings 136 along routes that do not include those task nodes. Of course, many other scheduling methods are known in the art and may be used to produce the workflows 134. Figure 6 illustrates an alternative system for generating workflows in accordance with yet another embodiment of the present invention. In the system, orders 140 are applied to a workflow engine 142. The orders may represent requests for products that are produced in a manufacturing environment represented by model 144. Model 144 may be a model organized in the fashion discussed above (e.g., as a directed graph with alternating series of state nodes and task nodes, etc.) or a model organized in another fashion. In response to orders 140 and/or updates 146 received from the real world environment represented by model 144, workflow engine 142 calls upon scheduler 148 to provide scheduling information. These calls are made in the form of schedule or reschedule commands 150. In response, scheduler 148 queries model 144 to determine available routes for product completion that may be available. For example, where model 144 is configured as described above, scheduler 148 may examine routes as alternating series of state nodes and task nodes, and assess each complete route through the model 144 on the basis of one or more selection criteria. These criteria may be as simple as finding a viable route (i.e., any complete path through the model), to more complex selections involving a determination of the effect of loading particular manufacturing processes (as represented by task nodes) with additional projects (corresponding to new orders, etc.), to costor value maximizing selection decisions. In any event, model 144 accurately reports the current state of the manufacturing environment to scheduler 148. This state is continually updated according to updates 152 provided by workflow engine 142. Workflow engine 142 receives update information (e.g., representing task completions, state availability, process availability, resource availability, etc.) and provides the necessary update information 152 that allows model 144 to accurately reflect the current state of the real world. Scheduler 148 relies on the real world state reflected by model 144 to produce route selection decisions 154. These route selection decisions (made in accordance with the scheduler's rules for such selections) form the basis for the workflows 156 returned by workflow engine 142. Such workflows may be returned any time new orders 140 are placed, in response to events that affect the real world environment represented by model 144, or upon user request (e.g., at the start of a new shift in the manufacturing environment). Thus, a method for generating workflows that may find application in a manufacturing environment has been described. Although the foregoing specification and accompanying figures discuss and illustrate specific embodiments, it should be appreciated that the present invention is to be measured only in terms of the claims that follow.

Claims: CLAIMS What is claimed is: 1. A method comprising generating from a declarative model of a real world environment a workflow of procedural steps to accomplish a process to be executed within the environment. 2. The method of claim 1 wherein the declarative model comprises a first number of state nodes and a second number of task nodes interconnected with the state nodes and generating a workflow comprises choosing one of a number of paths through the model, each of the paths comprising an alternating series of one or more of the state nodes and one or more of the task nodes with any predecessor state node in one of the paths representing a precondition for a subsequent task node along the one of the paths and any following state node of the subsequent task node along the one of the paths representing a result of applying one or more actions that correspond to that task node. 3. The method of claim 1 wherein generating a workflow comprises choosing any one of a plurality of feasible routes for completion of the process. 4. The method of claim 1 wherein generating a workflow comprises choosing an optimal route from a plurality of routes for completion of the process. 5. The method of claim 1 wherein generating a workflow comprises choosing one of a plurality of routes defined by the model according to one or more user-defined criteria for route selection. 6. The method of claim 5 wherein the model comprises a first number of state nodes and a second number of task nodes interconnected with the state nodes and choosing one of a plurality of routes comprises choosing one of a number of paths through the model, each of the paths comprising an alternating series of one or more of the state nodes and one or more of the task nodes with any predecessor state node in one of the paths representing a precondition for a subsequent task node along the one of the paths and any following state node of the subsequent task node along the one of the paths representing a result of applying one or more actions that correspond to that task node.. 7. The method of claim 6 wherein each of the routes define bills of resources for the real world environment and choosing a route comprises specifying one of the available bills of resources. 8. The method of claim 1 further comprising generating a new workflow in response to an update to the model and/or a new job request. 9. A workflow, comprising: a final product of the manufacturing process represented by a first state node of a directed graph; and one or more manufacturing processes required in the production of the final product and the corresponding preconditions thereto and results produced thereby, with the manufacturing processes represented by task nodes and the preconditions thereto and the results produced thereby represented by state nodes, the task nodes and state nodes arranged within the directed graph such that inputs to each of the task nodes represent required states therefor and outputs of each of the task nodes represent alternative states produced thereby, the first state node representing the output of one or more of the manufacturing processes represented by one or more of the task nodes. 10. The workflow of claim 9 wherein at least one of the task nodes represents consumption of a resource and/or an inventory item of a manufacturing environment. 11. The workflow of claim 9 wherein the state nodes represent reusable resources and/or consumable resources for a manufacturing environment. 12. The workflow of claim 9 wherein the state nodes are arranged in a hierarchy defined by the directed graph so as to comprise a bill of materials for a manufacturing environment. 13. A computer assisted scheduling system, comprising: a model of a real-world manufacturing environment; and a scheduler configured to optimize selection of one of a number of paths through the model to provide as a workflow in response to an order for a product produced by the manufacturing environment. 14. The system of claim 13 wherein the model is configured to receive updates reflecting changes in the real-world manufacturing environment. 15. The system of claim 14 wherein the changes comprise completed tasks. 16. The system of claim 14 wherein the changes comprise a change in the availability of one or more resources represented in the model.

Inventors: GOODROW CRISTOS J, NELSON PHILIP C, SMIRNOV YURI V, SOUNG YUH-WEN, WINNER JEFFREY B, GOODROW, CRISTOS, J., NELSON, PHILIP, C., SMIRNOV, YURI, V., SOUNG, YUH-WEN, WINNER, JEFFREY, B.
Applicants: IMPRESSE CORP, IMPRESSE CORPORATION
Application year: 1999
Main classification: G06F17
IPC codes: G06Q10