MTAT Business Process Management (BPM) (for Masters of IT) Lecture 8: Resource Allocation in Automated Business Processes

Transcription

1 MTAT Business Process Management (BPM) (for Masters of IT) Lecture 8: Resource Allocation in Automated Business Processes Marlon Dumas (based on lecture material by Arthur ter Hofstede and other members of the YAWL foundation:

2 Process Modelling Viewpoints What (functional perspective) What tasks/functions are happening in the process (manual or automated) When (control-flow perspective) In what order do they occur Which (data perspective) Which data is created/produced by the process and its tasks Who (resource perspective) Who performs these tasks 2

3 Path of a Work Item in YAWL 3

4 Resourcing Decision Points There are stages in a work item s lifecycle where resourcing decisions are to be made until the work item is placed in a work queue At each interaction point, the decision may be: system-initiated automatically performed by the system, using parameters set at design time, or user-initiated manually performed by a participant or administrator at runtime 4

5 Resourcing Decision Points The three decision points are: Offer: The work item is offered to one or more participants for execution. There is no obligation (from the system s perspective) for the participant to accept the offer. Allocate: The work item is allocated to a single participant, so that the participant is committed (willingly or not) to performing that work item at a later time. If the work item was previously offered to several other participants, the offer is withdrawn from them. Start: The work item is started by the allocated participant (i.e. enters executing state). 5

6 Default YAWL Worklist Handler 6

7 Resource Patterns Creation patterns: design-time work allocation directives Push patterns: workflow system proactively distributes work items Pull patterns: resources proactively identify and commit to work items Detour patterns: re-routing of work items Auto-start patterns: automated commencement Visibility patterns: observability of workflow activities Multiple resource patterns: work allocation involving multiple participants or resources 7

8 Work Item Lifecycle Resource Patterns S:offer-s S:create created S:offer-m offered to a single resource S:allocate R:allocate-s allocated to a single resource R:allocate-m R:start-s R:start R:start-m R:suspend suspended started R:fail R:resume R:complete completed offered to multiple resources failed 8

9 Creation Patterns Creation S:offer-s S:create created S:offer-m offered to a single resource S:allocate R:allocate-s allocated to a single resource R:allocate-m R:start-s R:start R:start-m R:suspend suspended started R:fail R:resume R:complete completed offered to multiple resources failed 9

10 Creation Patterns Creation Design time considerations relating to which resources may execute a work item at runtime Direct Allocation Role-Based Allocation Deferred Allocation Authorisation Separation of Duties Case Handling Retain Familiar Capability-Based Allocation History-Based Allocation Organisational Allocation 10

11 Direct Allocation 11

12 Role-based Allocation Creation: 2 The ability to specify at design time that a task can only be executed by resources which correspond to a given role. Actual decision for distribution deferred till runtime, can be influenced without changing workflow specification (thus providing more flexibility) resource/creation/wrp2_animation.php 12

13 Role-based Allocation in YAWL 13

14 YAWL Organisational Model 14

15 Separation of Duties Creation: 5 The ability to specify that two tasks must be allocated to different resources in a given workflow case. Also referred to as 4 eyes principle resource/creation/wrp5_animation.php 15

16 Separation of Duties in YAWL 16

17 Retain Familiar The opposite of the separation of duties Where several resources are available to undertake a work item, the ability to allocate a work item within a given workflow case to the same resource that undertook a preceding work item of the same case. resource/creation/wrp7_animation.php 17

18 Retain Familiar in YAWL 18

19 Push Patterns Push Correspond to situations where newly created work items are proactively routed to resources by the workflow system Key dimensions: Offer or allocation Single or multiple resources Basis of allocation Timing of distribution vs enablement 19

20 Push Patterns Push S:create S:offer-s created S:offer-m offered to a single resource S:allocate R:allocate-s allocated to a single resource R:allocate-m R:start-s R:start R:start-m R:suspend suspended started R:fail R:resume R:complete completed offered to multiple resources failed 20

21 Push Patterns Push Distribution by Offer - Single Resource Distribution by Offer - Multiple Resources Distribution by Allocation - Single Resource Random Allocation Round Robin Allocation Shortest Queue Early Distribution Distribution on Enablement Late Distribution 21

22 Shortest Queue Push: 17 The ability to allocate a work item to the resource that has the least number of work items allocated to it. Aims to expedite throughput Different definition of shortest queue possible One of a number of distribution strategies among possible (authorised) resources resource/push/wrp17_animation.php 22

23 Distribution by Allocation in YAWL 23

24 After Distribution Given appropriate privileges, a participant may: If a work item is allocated: deallocate it (removes themselves from the distribution set and redistribute the item); delegate it (to a member of their team ); or skip the work item (complete it immediately without first starting it) If a work item has started: reallocate it (to a member of their team), and in doing so may preserve the work done within the work item thus far (stateful reallocation), or to reset the work item data to its original values (stateless reallocation). 24

25 Detour Patterns Detour S:escalate-oo S:escalate-sm created offered to a single resource R:delegate offered to multiple resources allocated to a single resource S:escalate-am R:deallocate-am R:escalate-so S:deallocate-so R:deallocate-ao S:escalate-ao S:escalate-aa R:deallocate-sm S:escalate-sm R:suspend suspended started R:reallocation-no-state S:escalate-sa S:escalate-mm failed R:resume R:reallocationwith-state R:fail S:skip completed 25

26 Detour Patterns Detour Unplanned variations in work item routing Delegation Escalation Deallocation Stateful Reallocation Stateless Reallocation Suspension/Resumption Skipping 26

27 Delegation Detour: 27 The ability for a resource to allocate a work item previously allocated to it to another resource. Delegation allows a resource to re-route work items that it is unable to execute, e.g. because it is unavailable or because they do not wish to take on more work. wrp27_animation.php 27

28 Delegation in YAWL 28

29 Stateful Reallocation Detour: 30 The ability of a resource to allocate a work item to another resource without loss of state data. Provides a resource with the ability to offload both pending and currently executing work items to other resources whilst retaining work already performed. Centres on the ability to retain the current values of all data elements associated with the work item. Delegation also results in a work item being reassigned to another resource, but delegation only occurs for work items that have not yet been started wrp30_animation.php 29

30 Stateful Reallocation in YAWL 30

31 Recap: Resource specification in YAWL 31

32 For more info Detailed description of the workflow patterns: 32