Modeling Process Aware Information Systems with BPMN

Transcription

1 Modeling Process Aware Information Systems with BPMN Fabrizio Maria Maggi Based on lecture material by Marlon Dumas (University of Tartu, Estonia) and Wil van der Aalst (Eindhoven University of Technology, The Netherlands (c) Wil van der Aalst, Eindhoven University of Technology PN-1

2 Business Process Lifecycle (c) Wil van der Aalst, Eindhoven University of Technology

3 Purposes of process modeling Communication Documentation Analysis (e.g. simulation) Conceptual Executable Automation Testing Conceptual 3

4 (c) Wil van der Aalst, Eindhoven University of Technology 1. Introduction 2. Process Identification 3. Essential Process Modeling 4. Advanced Process Modeling 5. Process Discovery 6. Qualitative Process Analysis 7. Quantitative Process Analysis 8. Process Redesign 9. Process Automation 10.Process Intelligence

5 Business Process Lifecycle (c) Wil van der Aalst, Eindhoven University of Technology

6 Petri nets for modeling business processes [Aalst96] proposed to explicitly use Petri nets for business process modelling. Intuition: transitions represent the tasks that comprise a business process and places represent the conditions preceding and following the tasks. [Aalst96] W.M.P. van der Aalst. Three Good Reasons for Using a Petri-netbased Workflow Management System. Proc. of the International Working Conference on Information and Process Integration in Enterprises (IPIC 96), pp (1996) (c) Wil van der Aalst, Eindhoven University of Technology

7 Petri net example Order Fulfillment Example First, a take order task is executed. When pack order and check account tasks have been both completed, the credit check task is executed. If the customer has not sufficient credit the decline order runs and, finally, the return stock task ensures that the items from the order are returned to the warehouse. Then, pack order and check account tasks are executed in parallel. If the customer has sufficient credit remaining, the order is despatched. (c) Wil van der Aalst, Eindhoven University of Technology

8 Workflow nets: Definition The work [Aalst96] proposed a particular subclass of Petri nets, called Workflow nets (WF-nets) for modelling processes. A WF-net has a single start place and a single end place. This means that WF-nets closely correspond to real-life processes that tend to have a specific starting point and a specific end point. Every transition in the workflow net is on a path from the start to the end place. This ensures that each transition in a workflow net contributes to the progression of an executing instance towards its end state. Definition: A Petri net N = (P, T, F) is a WF-net (Workflow net) if and only if: There is one source place i P such that i = There is one sink place o P such that o = Every node x P T is on a path from i to o. (c) Wil van der Aalst, Eindhoven University of Technology

9 Exercise: Candidate WF-nets?

10 Workflow nets: Definition It is important to notice that the previous definition traces the minimal requirements for a WF-net. However, it does not guarantee that a candidate WF-net net will not potentially be subject to deadlocks. To ensure that any given process instance behaves in a predictable way, in [AH02] a number of so-called soundness criteria are formulated. [AH02] Wil M.P. van der Aalst and Kees M. van Hee. Workflow Management: Models, Methods, and Systems. The MIT Press (2002) (c) Wil van der Aalst, Eindhoven University of Technology

11 Workflow nets: Soundness Definition [soundness]: A procedure modeled in the form of a WF-net N = (P, T, F) is sound if and only if: [Option to Complete] Given an initial marking i, from every marking M reachable from i, there exists a firing sequence leading from state M to state o. This means that the any executing instance of the WF-net must eventually complete, i.e., net is free of deadlock and infinite loops. [Proper Completion] State o is the only state reachable from state i with at least one token in place o. Formally: When the net completes, no other task is still running and completion is signalled only once. At the moment of termination, there must be one token in the end place o and all other places in the WF-net must be empty. [No Dead Tasks] For every transition t, a marking M reachable from i can be found that enables t. The net does not contain any superfluous parts that can never be activated. In a nutshell, dead transitions are not allowed. (c) Wil van der Aalst, Eindhoven University of Technology

12 Workflow Net Constructs Automatic tasks execute as soon as they are enabled. User tasks are passed to human resources for execution once enabled. There are some notational enhancements for split and join constructs that simplify the specification of a WF-net. Petri nets can be used to understand their semantics. External tasks only proceed once Time tasks only proceed once they they are enabled and a required are enabled and a specified (timebased) message or signal is received from deadline occurs. the operating (c) Wil van environment. der Aalst, Eindhoven University of Technology

13 Parallelism: AND-split A B C According to the WfMC [WfMC], an AND-split is a point within the workflow where a single thread of control splits into two or more threads which are executed in parallel within the workflow, allowing multiple activities to be executed simultaneously. The execution of A enables both task B and task C. As a result, task B and task C are executed in parallel (in an arbitrary order). A AND-split B C In WF-nets, a special construct for AND-split is introduced. (c) Wil van der Aalst, Eindhoven University of Technology

14 Parallelism: AND-join B C D According to the WfMC [WfMC], an AND-join is a point in the workflow where two or more parallel executing activities converge into a single common thread of control. Task D is enabled after execution both B and C, i.e., D is used to synchronize two subflows. B C D AND-join In WF-nets, a special construct for AND-JOIN is introduced. (c) Wil van der Aalst, Eindhoven University of Technology

15 Conditional Routing: XOR-split A B C According to the WfMC [WfMC], a XOR-split is a point within the workflow where a single thread of control makes a decision upon which branch to take when encountered with multiple alternative workflow branches. Only one of the outgoing branches can be chosen (i.e., either task B or C can be executed). A XOR-split B C In WF-nets, a special construct for XOR-spit is introduced. (c) Wil van der Aalst, Eindhoven University of Technology

16 Conditional Routing: XOR-join B C B C D D XOR-join According to the WfMC [WfMC], a XOR-join is a point within the workflow where two or more alternative activity(s) workflow branches reconverge to a single common activity as the next step within the workflow. As no parallel activity execution has occurred at the join point, no synchronization is required. Therefore, D is enabled when B or C complete. In WF-nets, a special construct for XOR-JOIN is introduced. (c) Wil van der Aalst, Eindhoven University of Technology

17 WF-net example Order Fulfillment Process The take order task is externally triggered when an order request is received. The decline order task runs automatically with the customer receiving a notification either by or fax. Most tasks are undertaken by human resources (i.e., staff). (c) Wil van der Aalst, Eindhoven University of Technology

18 From Workflow Nets to BPMN A WF-net may be used to represent a process model, while the tokens represent process instances. Since tokens in WF-nets cannot be distinguished from each other, WF-nets can only host a single process instance per time. Moreover, WF-nets are not able to explicitly represent resources, data, etc. The Business Process Modeling Notation (BPMN) has been instead developed with the purpose of supporting the complete range of subdomains of business process modelling. BPMN is the ISO standard for modeling business processes (ISO/IEC 19510:2013), and creates a standardized bridge for the gap between the business process design and process implementation. The theoretical underpinnings of BPMN are largely based on WF-nets nets, adopting the same token passing for flow control. (c) Wil van der Aalst, Eindhoven University of Technology 18

19 Business Process Model and Notation (BPMN) OMG standard (nowadays BPMN 2.0) Supported by numerous tools: bpmn.org lists over 70 tools (c) Wil van der Aalst, Eindhoven University of Technology

20 BPMN from 10,000 miles A BPMN process model is a graph consisting of four types of core elements: start end activity event gateway sequence flow (c) Wil van der Aalst, Eindhoven University of Technology

21 A little bit more on events A start event triggers a new process instance by generating a token that traverses the sequence flow ( tokens source ) start event An end event signals that a process instance has completed with a given outcome by consuming a token ( tokens sink ) end event 21

22 Let s start modeling Order-to-cash An order-to-cash process is triggered by the receipt of a purchase order from a customer. Upon receipt, the purchase order has to be checked against the stock to determine if the the requested item(s) are available. Depending on stock availability the purchase order may be confirmed or rejected. If the purchase order is confirmed, an invoice is emitted and the goods requested are shipped. The process completes by archiving the order.

23 Let s start modeling break it down Order-to-cash An order-to-cash process is triggered by the receipt of a purchase order from a customer. Upon receipt, the purchase order has to be checked against the stock to determine if the the requested item(s) are available. Depending on stock availability the purchase order may be confirmed or rejected. If the purchase order is confirmed, an invoice is emitted and the goods requested are shipped. The process completes by archiving the order.

24 Let s start modeling break it down Order-to-cash An order-to-cash process is triggered by the receipt of a purchase order from a customer. Upon receipt, the purchase order has to be checked against the stock to determine if the the requested item(s) are available.

25 BPMN Model Order-to-cash Purchase order received Check stock availability 25

26 Let s start modeling break it down Order-to-cash An order-to-cash process is triggered by the receipt of a purchase order from a customer. Upon receipt, the purchase order has to be checked against the stock to determine if the the requested item(s) are available. Depending on stock availability the purchase order may be confirmed or rejected. If the purchase order is confirmed, an invoice is emitted and the goods requested are shipped. The process completes by archiving the order.

27 BPMN Model Order-to-cash Purchase order received start event activity Check stock availability Items not in stock Items in stock Reject order Order rejected split gateway Confirm order end event Emit invoice Ship goods Archive order end event Order fulfilled Event: noun + past-participle verb (e.g. insurance claim lodged) Naming conventions Activity: verb + noun (e.g. assess credit risk) 27

28 Execution of a process model The token game Order #1 Order #2 Order #3 Purchase order received Check stock availability Items not in stock Items in stock Reject order Confirm order Order rejected Emit invoice Ship goods Archive order Order fulfilled 28

29 Order-to-cash example revisited [ ] If the purchase order is confirmed, an invoice is emitted and the goods requested are shipped (in any order). The process completes by archiving the order. [ ] Purchase order received Check stock availability Items not in stock Items in stock Reject order Confirm order Order rejected Emit invoice Ship goods Archive order Order fulfilled 29

30 A little more on gateways: XOR Gateway condition An XOR Gateway captures decision points (XORsplit) and points where alternative flows are merged (XOR-join) XOR-split takes one outgoing branch condition XOR-join proceeds when one incoming branch has completed 30

31 Example: XOR Gateway Invoice checking process 5

32 A little more on gateways: AND Gateway An AND Gateway provides a mechanism to create and synchronize parallel flows. AND-split takes all outgoing branches AND-join proceeds when all incoming branches have completed 32

33 Example: AND Gateway Airport security check 33

34 Revised order-to-cash process model Items not in stock Reject order Order rejected Check stock availability XOR-split Send invoice Purchase order received Items in stock Confirm order AND-split AND-join Archive order Order fulfilled Ship goods 34

35 Petri nets to BPMN (c) Wil van der Aalst, Eindhoven University of Technology 35

36 Petri nets to BPMN (c) Wil van der Aalst, Eindhoven University of Technology 36

37 Petri nets to BPMN (c) Wil van der Aalst, Eindhoven University of Technology 37

38 Petri nets to BPMN (c) Wil van der Aalst, Eindhoven University of Technology 38

39 Petri nets to BPMN (c) Wil van der Aalst, Eindhoven University of Technology 39

40 Between XOR and AND Order distribution process A company has two warehouses that store different products: Amsterdam and Hamburg. When an order is received, it is distributed across these warehouses: if some of the relevant products are maintained in Amsterdam, a sub-order is sent there; likewise, if some relevant products are maintained in Hamburg, a sub-order is sent there. Afterwards, the order is registered and the process completes. 40

41 Solution 1 Order distribution process XOR-split XOR-join AND-split AND-join 41

42 Solution 2 Order distribution process AND-split AND-join XOR-split XOR-join 42

43 OR Gateway An OR Gateway provides a mechanism to create and synchronize n out of m parallel flows. cond 1 cond n OR-split takes one or more branches depending on conditions OR-join proceeds when all active incoming branches have completed 43

44 Solution using OR Gateway Order distribution process 44

45 Quick Note: Implicit vs. explicit gateways B B A = A C C 45

46 Guidelines: Naming Conventions 1. Give a name to every event and task 2. For tasks: verb followed by business object name and possibly complement Issue Driver Licence, Renew Licence via Agency 3. For message events: object + past participle Invoice received, Claim settled 4. Avoid generic verbs such as Handle, Record 5. Label each XOR-split with a condition Policy is invalid, Claim is inadmissible

47 Poll: Which model do you prefer?

48 One more guideline Model in blocks Pair up each AND-split with an AND-join and each XOR-split with a XORjoin, whenever possible Exception: sometimes a XOR-split leads to two end events different outcomes (cf. order management example)

49 Rework and repetition Address ministerial correspondence In the minister s office, when a ministerial inquiry has been received, it is registered into the system. Then the inquiry is investigated so that a ministerial response can be prepared. The finalization of a response includes the preparation of the response itself by the cabinet officer and the review of the response by the principal registrar. If the registrar does not approve the response, the latter needs to be prepared again by the cabinet officer for review. The process finishes only once the response has been approved. XOR-join: entry point XOR-split: exit point 49

50 Process Modelling Viewpoints Organization Who? Lanes & Pools What? Tasks Events When? Flows Gateways Which? Data / Materials Data Objects, Stores

51 Organizational Elements in BPMN Pools & Lanes Pool Captures a resource class. Generally used to model a business party (e.g. a whole company) Lane A resource sub-class within a pool. Generally used to model departments (e.g. shipping, finance), internal roles (e.g. Manager, Associate), software systems (e.g. ERP, CRM) Pool 51

52 Order-to-cash process with lanes

53 Message Flow A Message Flow represents a flow of information between two process parties (Pools) Message A Message Flow can connect: directly to the boundary of a Pool captures an informative message to/from that party to a specific activity or event within that Pool captures a message that triggers a specific activity/event within that party Pool 2 Pool 2 Receive Pool 1 Send Receive Pool 1 Send 53

54 Order-to-cash process with a black-box customer pool 54

55 Pools, Lanes and Flows: syntactic rules 1. A Sequence Flow cannot cross the boundaries of a Pool (message flows can) 2. Both Sequence Flow and Message Flow can cross the boundaries of Lanes 3. A Message Flow cannot connect two flow elements within the same pool

56 One more guideline Start modeling with one single white-box pool Initially, put the events and tasks in only one pool the pool of the party who is running the process Leave all other pools black-boxed Once you have modeled this way, and once the process diagram inside the white-box pool is complete, you can model the details (events and tasks) in the other pools if that is useful. In this course we will only model processes with one single whitebox pool all other pools are black-box

57 Process Modelling Viewpoints Data / Materials Which? Data Objects, Stores

58 Order-to-cash process, again Send invoice Purchase order received Check stock availability Items in stock Items not in stock Reject order Confirm order Ship goods Archive order Order fulfilled Order rejected The purchase order document serves as an input to the stock availability check. Based on the outcome of this check, the status of the document is updated, either to approved or rejected. If the order is approved, an invoice and a shipment notice are produced. 58

59 Model with information artifacts Purchase Order Purchase Order [checked] Purchase Order Send invoice Invoice Purchase Order Purchase order received Warehouse DB Check stock availability Items in stock Items not in stock Reject order Confirm order Order rejected Purchase Order Ship goods Shipment notice Archive order Orders DB Order fulfilled Purchase Order [rejected] Purchase Order [approved] 59

60 BPMN Information Artifacts Purchase order Invoice A Data Object captures an artifact required (input) or produced (output) by an activity. Can be physical or electronic Emit invoice Oracle CRM Retrieve client information Client info A Data Store is a place containing data objects that must be persisted beyond the duration of a process instance. It is used by an activity to store (as output) or retrieve (as input) data objects. 60

61 Quick Note: BPMN Text Annotations A Text Annotation is a mechanism to provide additional text information to the model reader Doesn t affect the flow of tokens through the process Includes packaging For blocked invoices Ship goods Clear vendor line items 61

62 BPMN Poster ( ) 62