In this chapter a domain model of mobile work was developed. The entities, state models, and objectives introduced are common for a large number of mobile business processes regardless of their actual business domain. In the following chapters this domain model will be utilized to develop a business modeling method that hides the mobility-driven properties and restrictions of mobile processes from the business modeler. In doing so the business mod-eler can focus on the business-specific properties of the processes to model.
Nonetheless, the modeling method is capable of introducing the mobility as-pects into the process models developed, as will be demonstrated in Chapter 3. Besides being the basis for the following chapters, the model can also be seen as a general reference model of mobile work.
Chapter 3
Simulation of Mobility
In this chapter we introduce a simulation method for mobile business pro-cesses and the environments they are executed in. The method helps to judge different improvement scenarios in business process reengineering projects.
It can thus be utilized to identify promising scenarios to be considered fur-ther in such projects. It consists of a CPN domain model representing the domain model introduced in Chapter 2, a CPN process model of mobile business processes, the Simple Mobile Process modeling Language (SMPL) derived from UML activity diagrams, and a transformation scheme to con-vert SMPL models to CPN process models. The CPN models are executable in a simulator and, thus, facilitate the method to provide simulation support in BPR projects. CPNs are a yet powerful but complex language the average business analyst is not familiar with. Therefore, the SMPL and an appro-priate transformation scheme are provided to increase the usability of the method by allowing for the modeling of mobile business processes with less effort than CPNs. The first section is concerned with the proper conditions of simulation runs and the requirements regarding the simulation method.
In the second section the CPN domain model is described in-depth, and the third section concentrates on the CPN process model to build mobile busi-ness processes for simulation. The fourth section introduces the SMPL as a subset of UML activity diagrams as well as the transformation scheme. The chapter concludes with a summary of the insights gained.
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40 CHAPTER 3. SIMULATION OF MOBILITY
3.1 Introduction to Dynamic Analysis and Simula-tion
3.1.1 Problems Addressed
Simulation systems often provide formal models to describe the situation to examine. Such formalisms as, e.g., Petri nets provide an enormous expres-sive power to the modeler of a specific problem. Even more flexibility and expressiveness Petri nets gain from extensions as, e.g., FUNSOFT nets [30]
or CPNs [55].
The drawback of Petri nets themselves and their empowering extensions lies in their expressive power since modeling real world processes requires a deep understanding of PNs’ formalism and semantics and leads to quite large nets with tens and hundreds of model elements [120]. This prevents the average business user or business analyst from modeling complex business scenarios with PNs [113; 128].
To a certain degree mobile environments consisting of entities as presented in Chapter 2 can be evaluated statically. Metrics like the worker-to-asset-ratio per region or the average depot-asset-distance can help to find differences between regions. Such information helps to identify canidate regions for op-timization efforts. Nonetheless, analyzing the mobile environment this way an enterprise is not capable of predicting the behaviour of the mobile en-vironment under the dynamic conditions of the operation of such systems.
We conceptualize dynamic conditions as operational situations demanding immediate reaction (e.g., combustion of a power substation) as well as sit-uations preventing the operation of parts of the workforce (e.g., traffic ac-cident with workers involved, sickness of workers). While the organization may know about the statistical distribution and frequency of such situa-tions, there is usually no knowledge about their influence on short-term, mid-term, and long-term operation and cost effects. Additionally, organiza-tions as, e.g., utilities may have to handle business processes with previously unknown progress and skill profiles.
Consider the damage search and repair process introduced in Section 2.1.3 (p. 15). Since the result of the search task depicted in Figure 2.5 determines the subsequent process steps, preliminary planning of the accordant cases is not suitable. The resulting sequence of planning and work execution cannot be analyzed in a static way but needs to be evaluated by dynamic simulation.
In addition to the situations introduced above, dynamic conditions arise if the scenario to be examined is no real scenario but the result of applying parametrization criteria as introduced in Section 2.5.4. For such scenarios, usually, no corresponding operational experience exists and thus the scenar-ios have to be simulated. The simulation method introduced here will thus
3.1. INTRODUCTION TO DYNAMIC ANALYSIS AND SIMULATION41 provide an analytical environment to evaluate the static modifications to mobile environments under conditions similar to real operation in mobile environments. The method allows for the simulation of a whole process en-vironment with different cases of different processes being executed in one and the same simulation instead of considering the processes separately.
CPNs [55]—an extension of Petri nets [92]—were chosen for the development of the simulation method because they have a complete formal basis, and tools for the modeling and simulation are available free of charge.
3.1.2 General Execution of Simulations
Figure 3.1 gives an overview of the basic activities when using simulation for the analysis of a mobile scenario. It is assumed that the domain model and the processes have already been loaded into the simulator.
actExecution of Simulations Loading of scenario data
Generation of business cases
Assignment of tasks to workers
Execution of mobile business cases
Evaluation of simulation results
Adjustment of mobile scenarios
Figure 3.1: General execution of dynamic analysis with simulations In the following, the activities are described in more detail:
1. Loading of scenario data imports all relevant data into the simulation model. Necessary data includes cases, workers, assets, and regions.
2. Generation of business cases: Based on how frequently the associated processes have to be executed, the loaded cases are assigned with pri-orities and arrival times. For the daily planning a list of cases is created while the urgent cases (see Definition 4.1, p. 88) arrive arbitrarily and as single cases.
3. Assignment of tasks to workers takes place in two different ways: Dur-ing daily plannDur-ing, a list of tasks is put into the daily schedules of the workers, representing their worklists. During the working day, ran-domly arriving urgent cases are added to the workers’ schedules, post-poning already planned tasks.
4. The execution of business cases represents the actual physical activ-ity of the workers. During this step timestamps are adjusted, traveling
42 CHAPTER 3. SIMULATION OF MOBILITY times, waiting times, and working times are accumulated and stored in the appropriate entities. As usual for simulations, the times are ran-domly distributed around the default values of the respective actions.
5. The evaluation of simulation results is splitted into the aggregation of necessary data by the simulation tool and the interpretation of the data by the user.
6. Based on the insights of the evaluation, the user might adjust the scenario’s parameters and initiate a new simulation run.