Despite the importance of qualitative assessments
in BPR, as noted in
Logistics-based modeling allows for analysing the time spent in executing a business process. The product lead time is defined as the time that passes between the moment a customer orders a product and the moment a product is delivered. In more detail, we can distinguish between processing time (the time actually worked on a job or operation), queue time (the time a jobs waits for a resource to become available), setup time (the time that passes between the moment a resource becomes available and the moment work on the job is started), wait time (the time that is spent waiting for another job to complete), and transport time (the time that is needed to move a job from a resource at a certain location to a resource at another location).
For a particular model, measurements may be obtained by running a series of simulations. Based on an analysis of the simulation results, alternative models may be proposed. For example, when the setup time for a job is relatively large, combining jobs into a single task for an employee may be more efficient. The LBM method offers a number of primitives, with associated graphic icons, from which a business process model may be constructed as a network of resources connected by transport arcs.
On a somewhat more abstract level, one may regard a business process simulation as consisting of data, flowing through the process, and handlers -- datahandlers -- performing some action on the data, such as transportation or specific operations.
An operation takes time, and is executed by an employee. Sometimes an operation results in more than one outgoing dataflow, for instance when it issues a request for additional information from a different department.
A waitqueue functions as a regular queue if it has one incoming dataflow, i.e. transport. When there are more incoming flows, it functions as a synchronized queue. Data from one flow is not passed on to the next datahandler until the data from the other flow has arrived. This happens for instance when work on a case cannot continue until additional information has arrived.
An external agent can either generate data according to some random number distribution, or take data, process it and pass it on to the next datahandler. In the latter case the agent functions as a black box: we only care how long the processing takes, not how it is exactly performed.
In addition, BPSIM offers the classes means (which can be used to model resources that are necessary to perform certain operations), and employee (which models the different people that perform the operations).
As one can see, the entities task and organization unit from LBM have no specific counterpart in BPSIM. The reason for this is that having no other datahandler between two operations already implies that those operations belong to the same task. Consequently they are executed with no time in between and by the same employee. Also, the fact that tasks are executed in different organization units does not add any information that changes the behaviour of the simulation. If it takes time to transport information between different units, then that time can be represented by the object of class transport between those units.
For the gathering and analyzing of results, the SIM classes
analysis are used.
The class agent, for example,
can be given a histogram to track the lead time
of data it has generated.
A script interface for BPSIM
Example -- requests for loans
Now let us take a look at an example business process model based on the objects made available in BPSIM. The example will detail possible situations before and after business process redesign has taken place.
In slide present-models
the visual representation of
the model resulting from the redesign effort is shown,
embedded in a Web page.
In addition to the model, the page contains
some results obtained by running a simulation.
For example, the text indicates that
an employee is busy handling incoming requests
only 33% of the time.
The histogram depicts the distribution
of the lead times of incoming loan requests,
that is the time that passes between receiving
a request and giving an answer.
The Web page further contains a button to
start a simulation run,
a description of the model
and links to alternative models.
On a technological level, we advocate the use of business process simulation. Nevertheless, to accomodate the social aspects, it is important to support the visualization of such models and their integration in an arbitrarily complex information context, such as the World Wide Web. Developing visualisation and animation support for simulation models is a topic of ongoing research. See section DIVA.
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