1. Structuredness
Now that we are familiar with resources and the organizational perspective, let's have a look at another viewpoint in process analysis: the structuredness of the process.
2. Control-flow
When we look at structuredness, we often speak of "control-flow". Control-flow refers to the different successions of activities, like in the example we saw of the different students. Recall that each case can be expressed as a sequence of activities. Each unique sequence is called a trace or process variant.
3. Further analysis
There are several ways to look at the variants of the process. On the one hand, we have several metrics which we can use to look at one specific aspect of the process: start and end activities, the distribution of the case length, which activities are always present in a case and which are exceptional, but also rework. For each of these topics, a metric similar to that of resource_frequency of can be calculated.
Besides these metrics, there are various visual tools to look at control-flow patterns: among which process map and trace explorer which we already saw in the last chapter, but also the precedence matrix.
Let's have a close look at the variants of the process in the emergency department.
4. Entry & Exit points
We see that there are 2 entry points and 2 exit points in this process. Most patient journey's start with a check-in and end with a check-out. However, some are handed over by the emergency vehicle crew. Not all patients are check-out, as some of them need further treatment in the hospital.
5. Rework
Another aspect is rework. When we talk about rework, it means that some activities in the process are done multiple times for the same case, which often is a source of inefficiencies and waste.
For example, consider this journey of a particular patient.
We distinguish two types of rework: Firstly, repetitions, when an activity is repeated later on in the case, such as surgery in this example. Secondly, self-loops, when an activity is repeated immediately, such as assessment.
The number of repetitions and self-loops can be analyzed at different levels of detail; activities, resources, cases, etc. As we will see in the exercises, this is true for all the available metrics.
It is important to keep in mind that while rework might be a bad sign in some processes, it may be an inherent necessity in others. Surely, we shouldn't suggest that the second surgery wasn't necesary, as it might have saved a patients live. However, it might also incidate that something went wrong the first time. We should always interpret the results in the correct context.
6. Precedence matrix
As a visual, we can create precendence matrices of process logs.
A precedence matrix shows the flows between activities in a more structured way compared to process map. It thus shows which activities precede other activities, which ones are at the start or the end, and which are the most important flows in the process.
7. Precedence matrix
The data for this matrix can be calculated using the precedence_matrix function, while the generic plot function provides easy visualizations. The values in the matrix can be absolute frequencies as well as relative frequencies.
8. Precedence matrix Example
Let's consider the precedence matrix from the hospital event data. On the bottom we can recognize the start activities, while on the right we can see the end activities.
We can also observe the activities for which self-loops occur, namely the Assesment (553 times) and the Surgery (455). Further, note that the Handover emergency entrace is always immediately followed by surgery or resusciation.
9. Let's practice!
Let's have a look at some exercises.