/faculteit technologie management PN-1 مهندسی مجدد فرآیندهای تجاری بخش دوم: مدلسازی فرآیندها به کمک Petri nets

/faculteit technologie management PN-2 High level Petri nets Extending classical Petri nets with color, time and hierarchy (informal introduction)

/faculteit technologie management PN-3 Extension with time (1) Each token has a timestamp. The timestamp specifies the earliest time when it can be consumed.

/faculteit technologie management PN-4 Extension with time (2) The enabling time of a transition is the maximum of the tokens to be consumed. If there are multiple tokens in a place, the earliest ones are consumed first. A transition with the smallest firing time will fire first. Transitions are eager, i.e., they fire as soon as they can. Produced token may have a delay. The timestamp of a produced token is the firing time plus its delay.

/faculteit technologie management PN-5 Running example: Enabling time Transition start is enabled at time 2 = max{0,min{2,4,4}}.

/faculteit technologie management PN-6 Running example: Delays Tokens for place busy get a delay of = firing time plus 3 time units

/faculteit technologie management PN-7 Running example: Transition start fired Transition start fired a time 2. Continue to play (timed) token game…

/faculteit technologie management PN-8

/faculteit technologie management PN-9

/faculteit technologie management PN-10 Exercise: Final state?

/faculteit technologie management PN-11 Exercise: Final state?

/faculteit technologie management PN-12 Extension with hierarchy Timed and colored Petri nets result in more compact models. However, for complex systems/processes the model does not fit on a single page. Moreover, putting things at the same level does not reflect the structure of the process/system. Many hierarchy concepts are possible. In this course we restrict ourselves to transition refinement.

/faculteit technologie management PN-13 Instead of

/faculteit technologie management PN-14 We can use hierarchy

/faculteit technologie management PN-15 Reuse Reuse saves design efforts. Hierarchy can have any number of levels Transition refinement can be used for top-down and bottom-up design

/faculteit technologie management PN-16 Exercise: model three (parallel) punch card desks in a hierarchical manner

17 Workflow management concepts A workflow definition is composed out of three parts: process definition: a description of the process itself resource classification: a classification of the resources to be used resource management rules: how to map work onto resources

18 Process definition A process definition specifies which steps are required and in what order they should be executed. (routing definition, procedure, workflow script) (purchase order, tax declarations, insurance claims process) A process definition consists of: Tasks (step, activity, process element) A task is atomic: commit or rollback. Conditions (state, phase, requirement) A condition is used to determine the enabling of a task. Subprocesses

19 Case A case is the 'thing' which needs to be processed by following the process definition. (process instance, job, project) (insurance claim, purchase order, complaint, loan application) The state of a case is determined by: case variables (case parameters ) The logistic attributes of a case which are used to route the case. conditions The requirements which are satisfied. (Application data) Beyond the scope of the WFMS.

20 Mapping a process definition onto Petri nets task condition case subprocess case variables

21 Sequential "first A then B" Parallel "A en B at the same time or in any order" –AND-split –AND-join Choice "A or B" –OR-split –OR-join Iteration "multiple A's" Routing of cases

22 Sequential routing "First A then B" AB

23 Parallel routing "A and B at the same time or in any order" A B AND-splitAND-join

24 Choice (1) "A or B" Overkill ?! A B OR-splitOR-join

25 Choice (2) Implicit choice: it depends on the "eagerness" of A and B! A B OR-split OR-join

26 Choice (3) Choice is explicit and may be based on logistic attributes! A B OR-split OR-join We use high-level Petri nets: tokens have values: case variables transitions determine the number of tokens produced: explicit OR- split

27 Syntactic sugaring AND-split AND-join Explicit OR-split OR-join

28 Iteration A B C B may be executed several times.