Transcript Process modeling

(Re)designing workflows
Tips and tricks.
Wil van der Aalst
Eindhoven University of Technology
Faculty of Technology Management
Department of Information and Technology
P.O. Box 513
5600 MB Eindhoven
The Netherlands
[email protected]
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Designing a workflow
begin
analyze
What?
analyze
objectives
How?
text
analyze
tasks and
processes
By whom?
process definition
resources and
scheduling
realization
resource classification
allocation rules
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Guidelines
• Start with the identification of a case.
What is the case?
– A case is often initiated by a customer (internal or external!)
– The process adds value to a case.
– A case has a life-cycle with begin and end.
– A case cannot be divided, but the work can.
• Determine the scope of the process as soon as possible.
• Determine the goal of a process (added value).
• Ignore the existence of resources during the design of a
process.
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Guidelines (2)
• Workflow modeling is an iterative process
– don't be afraid to make mistakes !!
– tasks are split and joined during the process
– use hierarchy: divide and conquer
• During the process a task should become a Logical Unit
of Work (LUW)
– atomic: commit or rollback
– a task is executed by the same person, at the same time, at the
same place
– avoid setup times (not too small)
– avoid large chucks (commit work should be limited)
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Extracting information from an existing process.
• Follow (paper) documents.
• Identify communication between people, teams and departments.
C
A
D
B
• Identify regular communication patterns (dialog/protocol).
A
request
B
C
command
information
information
request
response
message
sequence
chart
5
Reengineering workflows
• BPR: fundamental, radical, dramatic, process.
• Ignore existing processes and organization.
• Symptoms of a sick process:
– too many cases (in-process-inventory)
– (throughput time / service time)-ratio is too high
– service level (% in time) is too low
• Key performance indicators:
– throughput time, waiting time, service level
– occupation rate, number of cases, ...
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Guidelines for BPR
•
•
•
•
•
Check the necessity of each task.
Appoint a process manager.
Appoint case managers.
(Re)consider the size of each task.
(Re)consider the trade-off between a generic process
and multiple versions of the same process.
• (Re)consider the trade-off between a generic task and
multiple specialized tasks.
• Try to introduce more parallelism.
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Guidelines for BPR (2)
• Investigate new opportunities as a result of modern
technology.
• Optimize communication structure.
• Do not automate paper workflows!
• An electronic document is everywhere and nowhere.
• Use resources as if they are in the same room.
• Use a resource for what it is good at.
• Maintain as much flexibility as possible for the future.
• Avoid setup times by clustering tasks.
• Avoid setups and exploit routine by clustering cases.
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Design criteria
A process design is evaluated on the basis of four
key issues:
• time
• quality
• costs
• flexibility
Often there is a trade-off!
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Design criterion 1: Time
• Throughput time is composed of:
– service time (including set-up)
– transport time (can often be reduced to 0)
– waiting time
» sharing of resources (limited capacity)
» external communication (trigger time)
• There are several ways to evaluate throughput/waiting time:
– average
– variance
– service level
– ability to meet due dates
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Design criterion 2: Quality
• External: satisfaction of the customer
– Product: product meets specification/expectation.
– Process: the way the product is delivered (service level)
• Internal: conditions of work
– challenging
– varying
– controlling
There is often a positive correlation between external and
internal quality.
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Design criterion 3: Costs
• Type of costs
– fixed or variable,
– human, system (hardware/software), or external,
– processing, management, or support.
Note the trade-off between human/system-related costs.
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Design criterion 4: Flexibility
• The ability to react to changes.
• Flexibility of
– resources (ability to execute many tasks/new tasks)
– process (ability to handle various cases and changing workloads)
– management (ability to change rules/allocation)
– organization (ability to change the structure and responsiveness to
wishes of the market and business partners)
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Trade-off
Costs
Time
Flexibility
Quality
(T+/-,Q+/-,C+/-,F+/-)
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(1) Check the necessity of each task
A
B
check
• Every "check task" may be skipped: a trade-off between the
costs of the check and the costs of not doing the check.
A
B
auto-select
A
B
check
(T+,Q-,C+/-)
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(2) Appoint process/case managers
• A process manager monitors a process to see whether
there are bottlenecks, capacity problems and delayed
cases. Management instruments: motivating the people
involved in the process and control parameters.
• Case managers are assigned to a case. They are
responsible and execute as many tasks as possible for
the case. Benefits:
– commitment
– reduction of setup time
– one contact person
(Q+)
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(3) (Re)consider the size of each task
Pros: less work to commit, allows for specialization.
Cons: setup time, fragmentation, less commitment.
Pros: setup reduction, no fragmentation, more commitment.
Cons: more work to commit, one person needs to be qualified for both parts.
Also a trade-off between the complexity of the process
and the complexity of a task.
(T+,F-)
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(4) Trade-off:
one generic process or multiple versions
A
B
A
B
A\B
AB
B\A
Issues: simplicity, efficiency, controllability, maintainability, ...
(F+/-)
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(5) Trade-off:
one generic task or multiple specialized tasks
• Similar considerations.
• Specialization may lead to:
– the possibility to improve the allocation of resources
– more support when executing the task
– less flexibility
– a more complex process
– monotonicity
(T+,F-)
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(6) Introduce as much parallelism as possible
• More parallelism leads to improved performance:
reduction of waiting times and better use of capacity.
• Two types of parallelism: semi and real parallelism.
• IT infrastructures which allow for the sharing of data
and work enable parallelism.
A
B
A
B
(T++)
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• DBMS: sharing of data
– An electronic document is everywhere and nowhere!
• Network technology:
– communication: e-mail, WWW, ...
– distribution of information: transportation of data is fast, cheap
and convenient
• Automation of task or automated support of tasks
• Examples:
–
–
–
–
parallel (sharing of data)
customer involvement (sending forms via the WWW)
form synchronous to asynchronous communication
risk analysis based on historical data
(T+,Q+/-,C+/-,F-)
Do not automate paper workflows!
(7) Investigate opportunities of IT
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(8) Improve the allocation of resources
• Use resources as if they are in one room: avoid (at any
time!) the situation where one group of people is
overloaded and another (similar) group is waiting for work.
(T+,Q-)
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• Let people do work that the are good at. However, avoid
inflexibility as a result of specialization!
• Stimulate resources to build routine.
• When allocating work to resources, consider the
flexibility in the near future.
• Avoid setups as much as possible. There are two kinds
of setups: (1) case setups and (2) task setups.
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(9) Improve communication structure
• Reduce the number of messages to be exchanged
between the process and the environment.
• Try to automate the handling of messages
(send/receive).
• Avoid communication errors (EDI,WWW).
• If possible, use asynchronous instead of synchronous
communication.
A
request
B
C
command
information
information
request
(T+,Q+,C+/-,F-)
response
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(10) Order tasks based on cost/effect
• Consider the class of “knock-out processes”, e.g., hiring
people, handling claims, etc.
• Postphone expensive tasks until the end.
• Execute highly selective tasks first.
• In other words: order the tasks using the ratio
“costs/effect”.
(T+,C-)
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Case
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