1. CSS 496 Business Process Re-engineering for BS(CS)
Chapter 3: Enterprise modeling
Khurram Shahzad
Based on Petia, Marlon, Aalst, Johannesson and Weske Lectures

2. Enterprise Resource Planning
ERP definition
Software solution that addresses the enterprise needs taking the process view of an organisation to meet the organisational goals tightly integrating all functions of an enterprise
ERP means integration of
Processes
Databases
Tools
Applications
Interfaces

3. Enterprise Resource Planning
Drawback of ERP
Costly implementation
Dependency on vendor
Forgoing “best-of-breed” solutions
Solution: EAI
Enterprise Application Integration (EAI) is “the unrestricted sharing of data and business processes among any connected applications and data sources in the enterprise”.

4. Architectures of EAI
Message Broker
Process Broker
Point to Point

5. Goal Modeling How to make the goals of an enterprise explicit
Purpose of Goal Modeling
Describing the goals of an enterprise
Showing how the goals are interrelated
Finding problems that hinder goal fulfillment
Finding opportunities that facilitate goal fulfillment

6. Components of a Goal Model

7. An Example

8. An Example

9. A Goal Model for a Library

10. Goal Decomposition

11. Goal Decomposition

12. An Example
Per runs a campaign for president. His main opponent is Eva. Construct a goal model for the following:
Victory in the election
Get support from EU supporters
Get support from EU critics
Make the opponent look dishonourable
Per has misused credit cards
Eva has misused credit cards
Get many TV commercials
The budget is limited
Get financial support from big business
Get an image as independent
Get an image as trustworthy

13. Solution

14. Process Modeling

15. Process Modeling
Purpose of Process Modeling

16. Basic Concepts
Task - a logical unit of work that is carried out as a single whole
Resource - a person or a machine that can perform specific tasks
Activity - the performance of a task by a resource
Case - a sequence of activities performed to achieve some goal, an order, an insurance claim, a car assembly
Work item - the combination of a case and a task that is just to be carried out
Process - describes how a particular category of cases shall be managed
Control flow construct - sequence, selection, iteration, parallelisation

17. Process Modeling
Focus on
Petri Nets
BPMN
EPC

18. Petri Nets
Petri Nets – a formal approach based upon an established formalism for the modeling and analysis of processes
Advantages
It forces precise definitions
Ambiguities, uncertainties, and contradictions are thus prevented, in contrast to many informal diagramming techniques
Formalism often enables the use of number of analytical techniques

19. Petri Nets Classic Petri nets Simple process model
Just three elements: places, transitions and arcs.
Graphical and mathematical description.
Formal semantics and allows for analysis.

20. Petri Nets A Petri nets consists of places and transitions
Places are indicated by a circle
A transition is shown as a rectangle

21. Petri Nets Rules Connections are directed.
No connections between two places or two transitions.
Places may hold zero or more tokens.
First, we consider the case of at most one arc between two nodes.

22. Petri Nets
Enabled
A transition is enabled if each of its input places contains at least one token.
enabled
Not enabled
Not enabled

23. Petri Nets Firing fired
An enabled transition can fire (i.e., it occurs).
When it fires it consumes a token from each input place and produces a token for each output place.
fired

24. Petri Nets
Example

25. Petri Nets Enabled Transition
A transition is enabled when there is token in each of its input places

26. Petri Nets
Traffic Light Example

27. Petri Nets
Traffic Light Example

28. Petri Nets
Traffic Light Example

29. Role of a token Tokens can play the following roles:
a physical object, for example a product, a part, a drug, a person;
an information object, for example a message, a signal, a report;
a collection of objects, for example a truck with products, a warehouse with parts, or an address file;
an indicator of a state, for example the indicator of the state in which a process is, or the state of an object;
an indicator of a condition: the presence of a token indicates whether a certain condition is fulfilled.

30. Role of a place
a type of communication medium, like a telephone line, a middleman, or a communication network;
a buffer: for example, a depot, a queue or a post bin;
a geographical location, like a place in a warehouse, office or hospital;
a possible state or state condition: for example, the floor where an elevator is, or the condition that a specialist is available.

31. Role of a transition
an event: for example, starting an operation, the death of a patient, a change seasons or the switching of a traffic light from red to green;
a transformation of an object, like adapting a product, updating a database, or updating a document;
a transport of an object: for example, transporting goods, or sending a file.

32. Typical network structures
Causality
Parallelism (AND-split - AND-join)
Choice (XOR-split – XOR-join)
Iteration (XOR-join - XOR-split)
Capacity constraints
Feedback loop
Mutual exclusion
Alternating

33. Causality
Sequential routing

34. Parallelism

35. Parallelism: AND-split

36. Parallelism: AND-join

37. Choice: XOR-split

38. Choice: XOR-join

39. Iteration: 1 or more times
XOR-join before XOR-split

42. Limitations of classical Petri nets
Models tend to become large
Models cannot reflect temporal aspects

43. High-level Petri nets To tackle the problems identified.
Petri nets extended with:
Color (i.e., data)
Time
Hierarchy

44. Running example: Making punch cards
free desk employees
waiting patients
served patients
patient/ employees

45. Extension with color (1)
Tokens have a color (i.e., a data value)

46. Running example: Tokens are colored

47. Colored Petri Nets

48. Extension with time (1) Each token has a timestamp.
The timestamp specifies the earliest time when it can be consumed.

49. 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.

50. Petri Nets with Time
Every token gets a timestamp, indicating the time from which the token is available
A transition is enabled when each token to be consumed has a timestamp equal or prior to the current time
Each transition gives a delay to a token produced by the transition.

51. Running example: Enabling time
Transition start is enabled at time 2 = max{0,min{2,4,4}}.

52. Running example: Delays
Tokens for place busy get a delay of 3
@+3 = firing time plus 3 time units

53. Swimming School Exercise

54. Swimming School Exercise

55. Basic Workflow Concepts
Task - a logical unit of work that is carried out as a single whole
Resource - a person or a machine that can perform specific tasks
Activity - the performance of a task by a a resource
Case - a sequence of activities performed to achieve some goal, an order, an insurance claim, a car assembly
Work item - the combination of a case and a task that is just to be carried out
Process - describes how a particular category of cases shall be managed
Control flow construct - sequence, selection, iteration, parallelisation

56. Workflow Concepts in Petri Nets
Task - transition
Resource - token
Activity - transition that fires
Case - token
Work item - enabled transition
Process - Petri net
Control flow construct - modelled by places and transitions

57. Workflow Analysis Types of Analysis Qualitative (correctness)
Deadlock
Livelock …
Quantitative (performance)
Average completion time
Level of service

58. Reachability Analysis

59. Reachability Analysis

60. Reachability Analysis

61. Reachability Analysis

62. Reachability Graph Exercies

63. Reachability Graph Exercies

64. Quantitative Analysis
Resource utilization
Number of cases in progress
Waiting time
System time

65. Resource utilization Consider a process with one task
Number of cases in progress
λ is the number of incoming cases per time unit
µ is the number of cases the resource is able to process per time unit
The resource utilization is
ρ = λ / µ

66. Resource utilization λ = 4 µ = 5 The resource utilisation is
ρ = λ / µ = 4 / 5 = 0.8